Document v4l2 sink in README

It allows to send the video stream to /dev/videoN, so that it can be
captured (like a webcam) by any V4L2-compatible tool.

Refs #2232 <https://github.com/Genymobile/scrcpy/pull/2232>
Refs #2233 <https://github.com/Genymobile/scrcpy/pull/2233>

Co-authored-by: Romain Vimont <rom@rom1v.com>

README.md

@@ -198,6 +198,7 @@ If `--max-size` is also specified, resizing is applied after cropping.
 To lock the orientation of the mirroring:
 
 ```bash
+scrcpy --lock-video-orientation     # initial (current) orientation
 scrcpy --lock-video-orientation 0   # natural orientation
 scrcpy --lock-video-orientation 1   # 90° counterclockwise
 scrcpy --lock-video-orientation 2   # 180°
@@ -225,7 +226,9 @@ error will give the available encoders:
 scrcpy --encoder _
 ```
 
-### Recording
+### Capture
+
+#### Recording
 
 It is possible to record the screen while mirroring:
 
@@ -249,6 +252,58 @@ variation] does not impact the recorded file.
 [packet delay variation]: https://en.wikipedia.org/wiki/Packet_delay_variation
 
 
+#### v4l2loopback
+
+On Linux, it is possible to send the video stream to a v4l2 loopback device, so
+that the Android device can be opened like a webcam by any v4l2-capable tool.
+
+The module `v4l2loopback` must be installed:
+
+```bash
+sudo apt install v4l2loopback-dkms
+```
+
+To create a v4l2 device:
+
+```bash
+sudo modprobe v4l2loopback
+```
+
+This will create a new video device in `/dev/videoN`, where `N` is an integer
+(more [options](https://github.com/umlaeute/v4l2loopback#options) are available
+to create several devices or devices with specific IDs).
+
+To list the enabled devices:
+
+```bash
+# requires v4l-utils package
+v4l2-ctl --list-devices
+
+# simple but might be sufficient
+ls /dev/video*
+```
+
+To start scrcpy using a v4l2 sink:
+
+```bash
+scrcpy --v4l2-sink=/dev/videoN
+scrcpy --v4l2-sink=/dev/videoN -N  # --no-display to disable mirroring window
+```
+
+(replace `N` by the device ID, check with `ls /dev/video*`)
+
+Once enabled, you can open your video stream with a v4l2-capable tool:
+
+```bash
+ffplay -i /dev/videoN
+vlc v4l2:///dev/videoN   # VLC might add some buffering delay
+```
+
+For example, you could capture the video within [OBS].
+
+[OBS]: https://obsproject.com/
+
+
 ### Connection
 
 #### Wireless
@@ -491,18 +546,6 @@ scrcpy -Sw
 ```
 
 
-#### Render expired frames
-
-By default, to minimize latency, _scrcpy_ always renders the last decoded frame
-available, and drops any previous one.
-
-To force the rendering of all frames (at a cost of a possible increased
-latency), use:
-
-```bash
-scrcpy --render-expired-frames
-```
-
 #### Show touches
 
 For presentations, it may be useful to show physical touches (on the physical

app/meson.build

@@ -33,6 +33,11 @@ else
     src += [ 'src/sys/unix/process.c' ]
 endif
 
+v4l2_support = host_machine.system() == 'linux'
+if v4l2_support
+    src += [ 'src/v4l2_sink.c' ]
+endif
+
 check_functions = [
     'strdup'
 ]
@@ -49,6 +54,10 @@ if not get_option('crossbuild_windows')
         dependency('sdl2'),
     ]
 
+    if v4l2_support
+        dependencies += dependency('libavdevice')
+    endif
+
 else
 
     # cross-compile mingw32 build (from Linux to Windows)
@@ -124,6 +133,9 @@ conf.set('SERVER_DEBUGGER', get_option('server_debugger'))
 # select the debugger method ('old' for Android < 9, 'new' for Android >= 9)
 conf.set('SERVER_DEBUGGER_METHOD_NEW', get_option('server_debugger_method') == 'new')
 
+# enable V4L2 support (linux only)
+conf.set('HAVE_V4L2', v4l2_support)
+
 configure_file(configuration: conf, output: 'config.h')
 
 src_dir = include_directories('src')

app/scrcpy.1

@@ -83,10 +83,12 @@ Inject computer clipboard text as a sequence of key events on Ctrl+v (like MOD+S
 This is a workaround for some devices not behaving as expected when setting the device clipboard programmatically.
 
 .TP
-.BI "\-\-lock\-video\-orientation " value
+.BI "\-\-lock\-video\-orientation " [value]
-Lock video orientation to \fIvalue\fR. Possible values are -1 (unlocked), 0, 1, 2 and 3. Natural device orientation is 0, and each increment adds a 90 degrees otation counterclockwise.
+Lock video orientation to \fIvalue\fR. Possible values are "unlocked", "initial" (locked to the initial orientation), 0, 1, 2 and 3. Natural device orientation is 0, and each increment adds a 90 degrees otation counterclockwise.
 
-Default is -1 (unlocked).
+Default is "unlocked".
+
+Passing the option without argument is equivalent to passing "initial".
 
 .TP
 .BI "\-\-max\-fps " value
@@ -155,10 +157,6 @@ Supported names are currently "direct3d", "opengl", "opengles2", "opengles", "me
 .UR https://wiki.libsdl.org/SDL_HINT_RENDER_DRIVER
 .UE
 
-.TP
-.B \-\-render\-expired\-frames
-By default, to minimize latency, scrcpy always renders the last available decoded frame, and drops any previous ones. This flag forces to render all frames, at a cost of a possible increased latency.
-
 .TP
 .BI "\-\-rotation " value
 Set the initial display rotation. Possibles values are 0, 1, 2 and 3. Each increment adds a 90 degrees rotation counterclockwise.
@@ -187,6 +185,12 @@ Enable "show touches" on start, restore the initial value on exit.
 
 It only shows physical touches (not clicks from scrcpy).
 
+.TP
+.BI "\-\-v4l2-sink " /dev/videoN
+Output to v4l2loopback device.
+
+It requires to lock the video orientation (see --lock-video-orientation).
+
 .TP
 .BI "\-V, \-\-verbosity " value
 Set the log level ("debug", "info", "warn" or "error").

app/src/cli.c

@@ -79,12 +79,15 @@ scrcpy_print_usage(const char *arg0) {
         "        This is a workaround for some devices not behaving as\n"
         "        expected when setting the device clipboard programmatically.\n"
         "\n"
-        "    --lock-video-orientation value\n"
+        "    --lock-video-orientation [value]\n"
         "        Lock video orientation to value.\n"
-        "        Possible values are -1 (unlocked), 0, 1, 2 and 3.\n"
+        "        Possible values are \"unlocked\", \"initial\" (locked to the\n"
+        "        initial orientation), 0, 1, 2 and 3.\n"
         "        Natural device orientation is 0, and each increment adds a\n"
         "        90 degrees rotation counterclockwise.\n"
-        "        Default is -1 (unlocked).\n"
+        "        Default is \"unlocked\".\n"
+        "        Passing the option without argument is equivalent to passing\n"
+        "        \"initial\".\n"
         "\n"
         "    --max-fps value\n"
         "        Limit the frame rate of screen capture (officially supported\n"
@@ -143,12 +146,6 @@ scrcpy_print_usage(const char *arg0) {
         "        \"opengles2\", \"opengles\", \"metal\" and \"software\".\n"
         "        <https://wiki.libsdl.org/SDL_HINT_RENDER_DRIVER>\n"
         "\n"
-        "    --render-expired-frames\n"
-        "        By default, to minimize latency, scrcpy always renders the\n"
-        "        last available decoded frame, and drops any previous ones.\n"
-        "        This flag forces to render all frames, at a cost of a\n"
-        "        possible increased latency.\n"
-        "\n"
         "    --rotation value\n"
         "        Set the initial display rotation.\n"
         "        Possibles values are 0, 1, 2 and 3. Each increment adds a 90\n"
@@ -179,6 +176,13 @@ scrcpy_print_usage(const char *arg0) {
         "        on exit.\n"
         "        It only shows physical touches (not clicks from scrcpy).\n"
         "\n"
+#ifdef HAVE_V4L2
+        "    --v4l2-sink /dev/videoN\n"
+        "        Output to v4l2loopback device.\n"
+        "        It requires to lock the video orientation (see\n"
+        "        --lock-video-orientation).\n"
+        "\n"
+#endif
         "    -V, --verbosity value\n"
         "        Set the log level (debug, info, warn or error).\n"
 #ifndef NDEBUG
@@ -389,15 +393,27 @@ parse_max_fps(const char *s, uint16_t *max_fps) {
 }
 
 static bool
-parse_lock_video_orientation(const char *s, int8_t *lock_video_orientation) {
+parse_lock_video_orientation(const char *s,
+                             enum sc_lock_video_orientation *lock_mode) {
+    if (!s || !strcmp(s, "initial")) {
+        // Without argument, lock the initial orientation
+        *lock_mode = SC_LOCK_VIDEO_ORIENTATION_INITIAL;
+        return true;
+    }
+
+    if (!strcmp(s, "unlocked")) {
+        *lock_mode = SC_LOCK_VIDEO_ORIENTATION_UNLOCKED;
+        return true;
+    }
+
     long value;
-    bool ok = parse_integer_arg(s, &value, false, -1, 3,
+    bool ok = parse_integer_arg(s, &value, false, 0, 3,
                                 "lock video orientation");
     if (!ok) {
         return false;
     }
 
-    *lock_video_orientation = (int8_t) value;
+    *lock_mode = (enum sc_lock_video_orientation) value;
     return true;
 }
 
@@ -667,6 +683,7 @@ guess_record_format(const char *filename) {
 #define OPT_LEGACY_PASTE           1024
 #define OPT_ENCODER_NAME           1025
 #define OPT_POWER_OFF_ON_CLOSE     1026
+#define OPT_V4L2_SINK              1027
 
 bool
 scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
@@ -686,7 +703,7 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"fullscreen",             no_argument,       NULL, 'f'},
         {"help",                   no_argument,       NULL, 'h'},
         {"legacy-paste",           no_argument,       NULL, OPT_LEGACY_PASTE},
-        {"lock-video-orientation", required_argument, NULL,
+        {"lock-video-orientation", optional_argument, NULL,
                                                   OPT_LOCK_VIDEO_ORIENTATION},
         {"max-fps",                required_argument, NULL, OPT_MAX_FPS},
         {"max-size",               required_argument, NULL, 'm'},
@@ -708,6 +725,9 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
         {"show-touches",           no_argument,       NULL, 't'},
         {"stay-awake",             no_argument,       NULL, 'w'},
         {"turn-screen-off",        no_argument,       NULL, 'S'},
+#ifdef HAVE_V4L2
+        {"v4l2-sink",              required_argument, NULL, OPT_V4L2_SINK},
+#endif
         {"verbosity",              required_argument, NULL, 'V'},
         {"version",                no_argument,       NULL, 'v'},
         {"window-title",           required_argument, NULL, OPT_WINDOW_TITLE},
@@ -771,7 +791,8 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
                 }
                 break;
             case OPT_LOCK_VIDEO_ORIENTATION:
-                if (!parse_lock_video_orientation(optarg, &opts->lock_video_orientation)) {
+                if (!parse_lock_video_orientation(optarg,
+                        &opts->lock_video_orientation)) {
                     return false;
                 }
                 break;
@@ -816,7 +837,8 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
                 opts->stay_awake = true;
                 break;
             case OPT_RENDER_EXPIRED_FRAMES:
-                opts->render_expired_frames = true;
+                LOGW("Option --render-expired-frames has been removed. This "
+                     "flag has been ignored.");
                 break;
             case OPT_WINDOW_TITLE:
                 opts->window_title = optarg;
@@ -890,16 +912,36 @@ scrcpy_parse_args(struct scrcpy_cli_args *args, int argc, char *argv[]) {
             case OPT_POWER_OFF_ON_CLOSE:
                 opts->power_off_on_close = true;
                 break;
+#ifdef HAVE_V4L2
+            case OPT_V4L2_SINK:
+                opts->v4l2_device = optarg;
+                break;
+#endif
             default:
                 // getopt prints the error message on stderr
                 return false;
         }
     }
 
+#ifdef HAVE_V4L2
+    if (!opts->display && !opts->record_filename && !opts->v4l2_device) {
+        LOGE("-N/--no-display requires either screen recording (-r/--record)"
+             " or sink to v4l2loopback device (--v4l2-sink)");
+        return false;
+    }
+
+    if (opts->v4l2_device && opts->lock_video_orientation
+                             == SC_LOCK_VIDEO_ORIENTATION_UNLOCKED) {
+        LOGI("Video orientation is locked for v4l2 sink. "
+             "See --lock-video-orientation.");
+        opts->lock_video_orientation = SC_LOCK_VIDEO_ORIENTATION_INITIAL;
+    }
+#else
     if (!opts->display && !opts->record_filename) {
         LOGE("-N/--no-display requires screen recording (-r/--record)");
         return false;
     }
+#endif
 
     int index = optind;
     if (index < argc) {

app/src/common.h

@@ -8,4 +8,7 @@
 #define MIN(X,Y) (X) < (Y) ? (X) : (Y)
 #define MAX(X,Y) (X) > (Y) ? (X) : (Y)
 
+#define container_of(ptr, type, member) \
+    ((type *) (((char *) (ptr)) - offsetof(type, member)))
+
 #endif

app/src/compat.h

@@ -8,20 +8,9 @@
 # define _DARWIN_C_SOURCE
 #endif
 
-#include <libavcodec/version.h>
 #include <libavformat/version.h>
 #include <SDL2/SDL_version.h>
 
-// In ffmpeg/doc/APIchanges:
-// 2016-04-11 - 6f69f7a / 9200514 - lavf 57.33.100 / 57.5.0 - avformat.h
-//   Add AVStream.codecpar, deprecate AVStream.codec.
-#if    (LIBAVFORMAT_VERSION_MICRO >= 100 /* FFmpeg */ && \
-        LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(57, 33, 100)) \
-    || (LIBAVFORMAT_VERSION_MICRO < 100 && /* Libav */ \
-        LIBAVFORMAT_VERSION_INT >= AV_VERSION_INT(57, 5, 0))
-# define SCRCPY_LAVF_HAS_NEW_CODEC_PARAMS_API
-#endif
-
 // In ffmpeg/doc/APIchanges:
 // 2018-02-06 - 0694d87024 - lavf 58.9.100 - avformat.h
 //   Deprecate use of av_register_input_format(), av_register_output_format(),
@@ -33,15 +22,6 @@
 # define SCRCPY_LAVF_REQUIRES_REGISTER_ALL
 #endif
 
-// In ffmpeg/doc/APIchanges:
-// 2016-04-21 - 7fc329e - lavc 57.37.100 - avcodec.h
-//   Add a new audio/video encoding and decoding API with decoupled input
-//   and output -- avcodec_send_packet(), avcodec_receive_frame(),
-//   avcodec_send_frame() and avcodec_receive_packet().
-#if LIBAVCODEC_VERSION_INT >= AV_VERSION_INT(57, 37, 100)
-# define SCRCPY_LAVF_HAS_NEW_ENCODING_DECODING_API
-#endif
-
 #if SDL_VERSION_ATLEAST(2, 0, 5)
 // <https://wiki.libsdl.org/SDL_HINT_MOUSE_FOCUS_CLICKTHROUGH>
 # define SCRCPY_SDL_HAS_HINT_MOUSE_FOCUS_CLICKTHROUGH

app/src/decoder.c

@@ -4,14 +4,40 @@
 
 #include "events.h"
 #include "video_buffer.h"
+#include "trait/frame_sink.h"
 #include "util/log.h"
 
-void
+/** Downcast packet_sink to decoder */
-decoder_init(struct decoder *decoder, struct video_buffer *vb) {
+#define DOWNCAST(SINK) container_of(SINK, struct decoder, packet_sink)
-    decoder->video_buffer = vb;
+
+static void
+decoder_close_first_sinks(struct decoder *decoder, unsigned count) {
+    while (count) {
+        struct sc_frame_sink *sink = decoder->sinks[--count];
+        sink->ops->close(sink);
+    }
 }
 
-bool
+static inline void
+decoder_close_sinks(struct decoder *decoder) {
+    decoder_close_first_sinks(decoder, decoder->sink_count);
+}
+
+static bool
+decoder_open_sinks(struct decoder *decoder) {
+    for (unsigned i = 0; i < decoder->sink_count; ++i) {
+        struct sc_frame_sink *sink = decoder->sinks[i];
+        if (!sink->ops->open(sink)) {
+            LOGE("Could not open frame sink %d", i);
+            decoder_close_first_sinks(decoder, i);
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static bool
 decoder_open(struct decoder *decoder, const AVCodec *codec) {
     decoder->codec_ctx = avcodec_alloc_context3(codec);
     if (!decoder->codec_ctx) {
@@ -25,52 +51,106 @@ decoder_open(struct decoder *decoder, const AVCodec *codec) {
         return false;
     }
 
+    decoder->frame = av_frame_alloc();
+    if (!decoder->frame) {
+        LOGE("Could not create decoder frame");
+        avcodec_close(decoder->codec_ctx);
+        avcodec_free_context(&decoder->codec_ctx);
+        return false;
+    }
+
+    if (!decoder_open_sinks(decoder)) {
+        LOGE("Could not open decoder sinks");
+        av_frame_free(&decoder->frame);
+        avcodec_close(decoder->codec_ctx);
+        avcodec_free_context(&decoder->codec_ctx);
+        return false;
+    }
+
     return true;
 }
 
-void
+static void
 decoder_close(struct decoder *decoder) {
+    decoder_close_sinks(decoder);
+    av_frame_free(&decoder->frame);
     avcodec_close(decoder->codec_ctx);
     avcodec_free_context(&decoder->codec_ctx);
 }
 
-bool
+static bool
+push_frame_to_sinks(struct decoder *decoder, const AVFrame *frame) {
+    for (unsigned i = 0; i < decoder->sink_count; ++i) {
+        struct sc_frame_sink *sink = decoder->sinks[i];
+        if (!sink->ops->push(sink, frame)) {
+            LOGE("Could not send frame to sink %d", i);
+            return false;
+        }
+    }
+
+    return true;
+}
+
+static bool
 decoder_push(struct decoder *decoder, const AVPacket *packet) {
-// the new decoding/encoding API has been introduced by:
+    bool is_config = packet->pts == AV_NOPTS_VALUE;
-// <http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=7fc329e2dd6226dfecaa4a1d7adf353bf2773726>
+    if (is_config) {
-#ifdef SCRCPY_LAVF_HAS_NEW_ENCODING_DECODING_API
+        // nothing to do
-    int ret;
+        return true;
-    if ((ret = avcodec_send_packet(decoder->codec_ctx, packet)) < 0) {
+    }
+
+    int ret = avcodec_send_packet(decoder->codec_ctx, packet);
+    if (ret < 0 && ret != AVERROR(EAGAIN)) {
         LOGE("Could not send video packet: %d", ret);
         return false;
     }
-    ret = avcodec_receive_frame(decoder->codec_ctx,
+    ret = avcodec_receive_frame(decoder->codec_ctx, decoder->frame);
-                                decoder->video_buffer->producer_frame);
     if (!ret) {
         // a frame was received
-        video_buffer_producer_offer_frame(decoder->video_buffer);
+        bool ok = push_frame_to_sinks(decoder, decoder->frame);
+        // A frame lost should not make the whole pipeline fail. The error, if
+        // any, is already logged.
+        (void) ok;
     } else if (ret != AVERROR(EAGAIN)) {
         LOGE("Could not receive video frame: %d", ret);
         return false;
     }
-#else
-    int got_picture;
-    int len = avcodec_decode_video2(decoder->codec_ctx,
-                                    decoder->video_buffer->producer_frame,
-                                    &got_picture,
-                                    packet);
-    if (len < 0) {
-        LOGE("Could not decode video packet: %d", len);
-        return false;
-    }
-    if (got_picture) {
-        video_buffer_producer_offer_frame(decoder->video_buffer);
-    }
-#endif
     return true;
 }
 
-void
+static bool
-decoder_interrupt(struct decoder *decoder) {
+decoder_packet_sink_open(struct sc_packet_sink *sink, const AVCodec *codec) {
-    video_buffer_interrupt(decoder->video_buffer);
+    struct decoder *decoder = DOWNCAST(sink);
+    return decoder_open(decoder, codec);
+}
+
+static void
+decoder_packet_sink_close(struct sc_packet_sink *sink) {
+    struct decoder *decoder = DOWNCAST(sink);
+    decoder_close(decoder);
+}
+
+static bool
+decoder_packet_sink_push(struct sc_packet_sink *sink, const AVPacket *packet) {
+    struct decoder *decoder = DOWNCAST(sink);
+    return decoder_push(decoder, packet);
+}
+
+void
+decoder_init(struct decoder *decoder) {
+    static const struct sc_packet_sink_ops ops = {
+        .open = decoder_packet_sink_open,
+        .close = decoder_packet_sink_close,
+        .push = decoder_packet_sink_push,
+    };
+
+    decoder->packet_sink.ops = &ops;
+}
+
+void
+decoder_add_sink(struct decoder *decoder, struct sc_frame_sink *sink) {
+    assert(decoder->sink_count < DECODER_MAX_SINKS);
+    assert(sink);
+    assert(sink->ops);
+    decoder->sinks[decoder->sink_count++] = sink;
 }

app/src/decoder.h

@@ -3,30 +3,27 @@
 
 #include "common.h"
 
+#include "trait/packet_sink.h"
+
 #include <stdbool.h>
 #include <libavformat/avformat.h>
 
-struct video_buffer;
+#define DECODER_MAX_SINKS 2
 
 struct decoder {
-    struct video_buffer *video_buffer;
+    struct sc_packet_sink packet_sink; // packet sink trait
+
+    struct sc_frame_sink *sinks[DECODER_MAX_SINKS];
+    unsigned sink_count;
 
     AVCodecContext *codec_ctx;
+    AVFrame *frame;
 };
 
 void
-decoder_init(struct decoder *decoder, struct video_buffer *vb);
+decoder_init(struct decoder *decoder);
-
-bool
-decoder_open(struct decoder *decoder, const AVCodec *codec);
 
 void
-decoder_close(struct decoder *decoder);
+decoder_add_sink(struct decoder *decoder, struct sc_frame_sink *sink);
-
-bool
-decoder_push(struct decoder *decoder, const AVPacket *packet);
-
-void
-decoder_interrupt(struct decoder *decoder);
 
 #endif

app/src/main.c

@@ -6,6 +6,9 @@
 #include <stdbool.h>
 #include <unistd.h>
 #include <libavformat/avformat.h>
+#ifdef HAVE_V4L2
+# include <libavdevice/avdevice.h>
+#endif
 #define SDL_MAIN_HANDLED // avoid link error on Linux Windows Subsystem
 #include <SDL2/SDL.h>
 
@@ -28,6 +31,11 @@ print_version(void) {
     fprintf(stderr, " - libavutil %d.%d.%d\n", LIBAVUTIL_VERSION_MAJOR,
                                                LIBAVUTIL_VERSION_MINOR,
                                                LIBAVUTIL_VERSION_MICRO);
+#ifdef HAVE_V4L2
+    fprintf(stderr, " - libavdevice %d.%d.%d\n", LIBAVDEVICE_VERSION_MAJOR,
+                                                 LIBAVDEVICE_VERSION_MINOR,
+                                                 LIBAVDEVICE_VERSION_MICRO);
+#endif
 }
 
 static SDL_LogPriority
@@ -90,6 +98,12 @@ main(int argc, char *argv[]) {
     av_register_all();
 #endif
 
+#ifdef HAVE_V4L2
+    if (args.opts.v4l2_device) {
+        avdevice_register_all();
+    }
+#endif
+
     if (avformat_network_init()) {
         return 1;
     }

app/src/recorder.c

@@ -4,6 +4,10 @@
 #include <libavutil/time.h>
 
 #include "util/log.h"
+#include "util/str_util.h"
+
+/** Downcast packet_sink to recorder */
+#define DOWNCAST(SINK) container_of(SINK, struct recorder, packet_sink)
 
 static const AVRational SCRCPY_TIME_BASE = {1, 1000000}; // timestamps in us
 
@@ -19,8 +23,8 @@ find_muxer(const char *name) {
 #else
         oformat = av_oformat_next(oformat);
 #endif
-        // until null or with name "mp4"
+        // until null or containing the requested name
-    } while (oformat && strcmp(oformat->name, name));
+    } while (oformat && !strlist_contains(oformat->name, ',', name));
     return oformat;
 }
 
@@ -57,50 +61,6 @@ recorder_queue_clear(struct recorder_queue *queue) {
     }
 }
 
-bool
-recorder_init(struct recorder *recorder,
-              const char *filename,
-              enum sc_record_format format,
-              struct size declared_frame_size) {
-    recorder->filename = strdup(filename);
-    if (!recorder->filename) {
-        LOGE("Could not strdup filename");
-        return false;
-    }
-
-    bool ok = sc_mutex_init(&recorder->mutex);
-    if (!ok) {
-        LOGC("Could not create mutex");
-        free(recorder->filename);
-        return false;
-    }
-
-    ok = sc_cond_init(&recorder->queue_cond);
-    if (!ok) {
-        LOGC("Could not create cond");
-        sc_mutex_destroy(&recorder->mutex);
-        free(recorder->filename);
-        return false;
-    }
-
-    queue_init(&recorder->queue);
-    recorder->stopped = false;
-    recorder->failed = false;
-    recorder->format = format;
-    recorder->declared_frame_size = declared_frame_size;
-    recorder->header_written = false;
-    recorder->previous = NULL;
-
-    return true;
-}
-
-void
-recorder_destroy(struct recorder *recorder) {
-    sc_cond_destroy(&recorder->queue_cond);
-    sc_mutex_destroy(&recorder->mutex);
-    free(recorder->filename);
-}
-
 static const char *
 recorder_get_format_name(enum sc_record_format format) {
     switch (format) {
@@ -110,88 +70,6 @@ recorder_get_format_name(enum sc_record_format format) {
     }
 }
 
-bool
-recorder_open(struct recorder *recorder, const AVCodec *input_codec) {
-    const char *format_name = recorder_get_format_name(recorder->format);
-    assert(format_name);
-    const AVOutputFormat *format = find_muxer(format_name);
-    if (!format) {
-        LOGE("Could not find muxer");
-        return false;
-    }
-
-    recorder->ctx = avformat_alloc_context();
-    if (!recorder->ctx) {
-        LOGE("Could not allocate output context");
-        return false;
-    }
-
-    // contrary to the deprecated API (av_oformat_next()), av_muxer_iterate()
-    // returns (on purpose) a pointer-to-const, but AVFormatContext.oformat
-    // still expects a pointer-to-non-const (it has not be updated accordingly)
-    // <https://github.com/FFmpeg/FFmpeg/commit/0694d8702421e7aff1340038559c438b61bb30dd>
-    recorder->ctx->oformat = (AVOutputFormat *) format;
-
-    av_dict_set(&recorder->ctx->metadata, "comment",
-                "Recorded by scrcpy " SCRCPY_VERSION, 0);
-
-    AVStream *ostream = avformat_new_stream(recorder->ctx, input_codec);
-    if (!ostream) {
-        avformat_free_context(recorder->ctx);
-        return false;
-    }
-
-#ifdef SCRCPY_LAVF_HAS_NEW_CODEC_PARAMS_API
-    ostream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
-    ostream->codecpar->codec_id = input_codec->id;
-    ostream->codecpar->format = AV_PIX_FMT_YUV420P;
-    ostream->codecpar->width = recorder->declared_frame_size.width;
-    ostream->codecpar->height = recorder->declared_frame_size.height;
-#else
-    ostream->codec->codec_type = AVMEDIA_TYPE_VIDEO;
-    ostream->codec->codec_id = input_codec->id;
-    ostream->codec->pix_fmt = AV_PIX_FMT_YUV420P;
-    ostream->codec->width = recorder->declared_frame_size.width;
-    ostream->codec->height = recorder->declared_frame_size.height;
-#endif
-
-    int ret = avio_open(&recorder->ctx->pb, recorder->filename,
-                        AVIO_FLAG_WRITE);
-    if (ret < 0) {
-        LOGE("Failed to open output file: %s", recorder->filename);
-        // ostream will be cleaned up during context cleaning
-        avformat_free_context(recorder->ctx);
-        return false;
-    }
-
-    LOGI("Recording started to %s file: %s", format_name, recorder->filename);
-
-    return true;
-}
-
-void
-recorder_close(struct recorder *recorder) {
-    if (recorder->header_written) {
-        int ret = av_write_trailer(recorder->ctx);
-        if (ret < 0) {
-            LOGE("Failed to write trailer to %s", recorder->filename);
-            recorder->failed = true;
-        }
-    } else {
-        // the recorded file is empty
-        recorder->failed = true;
-    }
-    avio_close(recorder->ctx->pb);
-    avformat_free_context(recorder->ctx);
-
-    if (recorder->failed) {
-        LOGE("Recording failed to %s", recorder->filename);
-    } else {
-        const char *format_name = recorder_get_format_name(recorder->format);
-        LOGI("Recording complete to %s file: %s", format_name, recorder->filename);
-    }
-}
-
 static bool
 recorder_write_header(struct recorder *recorder, const AVPacket *packet) {
     AVStream *ostream = recorder->ctx->streams[0];
@@ -205,13 +83,8 @@ recorder_write_header(struct recorder *recorder, const AVPacket *packet) {
     // copy the first packet to the extra data
     memcpy(extradata, packet->data, packet->size);
 
-#ifdef SCRCPY_LAVF_HAS_NEW_CODEC_PARAMS_API
     ostream->codecpar->extradata = extradata;
     ostream->codecpar->extradata_size = packet->size;
-#else
-    ostream->codec->extradata = extradata;
-    ostream->codec->extradata_size = packet->size;
-#endif
 
     int ret = avformat_write_header(recorder->ctx, NULL);
     if (ret < 0) {
@@ -317,7 +190,26 @@ run_recorder(void *data) {
             sc_mutex_unlock(&recorder->mutex);
             break;
         }
+    }
 
+    if (!recorder->failed) {
+        if (recorder->header_written) {
+            int ret = av_write_trailer(recorder->ctx);
+            if (ret < 0) {
+                LOGE("Failed to write trailer to %s", recorder->filename);
+                recorder->failed = true;
+            }
+        } else {
+            // the recorded file is empty
+            recorder->failed = true;
+        }
+    }
+
+    if (recorder->failed) {
+        LOGE("Recording failed to %s", recorder->filename);
+    } else {
+        const char *format_name = recorder_get_format_name(recorder->format);
+        LOGI("Recording complete to %s file: %s", format_name, recorder->filename);
     }
 
     LOGD("Recorder thread ended");
@@ -325,34 +217,108 @@ run_recorder(void *data) {
     return 0;
 }
 
-bool
+static bool
-recorder_start(struct recorder *recorder) {
+recorder_open(struct recorder *recorder, const AVCodec *input_codec) {
-    LOGD("Starting recorder thread");
+    bool ok = sc_mutex_init(&recorder->mutex);
-
-    bool ok = sc_thread_create(&recorder->thread, run_recorder, "recorder",
-                               recorder);
     if (!ok) {
-        LOGC("Could not start recorder thread");
+        LOGC("Could not create mutex");
         return false;
     }
 
-    return true;
+    ok = sc_cond_init(&recorder->queue_cond);
+    if (!ok) {
+        LOGC("Could not create cond");
+        goto error_mutex_destroy;
     }
 
-void
+    queue_init(&recorder->queue);
-recorder_stop(struct recorder *recorder) {
+    recorder->stopped = false;
+    recorder->failed = false;
+    recorder->header_written = false;
+    recorder->previous = NULL;
+
+    const char *format_name = recorder_get_format_name(recorder->format);
+    assert(format_name);
+    const AVOutputFormat *format = find_muxer(format_name);
+    if (!format) {
+        LOGE("Could not find muxer");
+        goto error_cond_destroy;
+    }
+
+    recorder->ctx = avformat_alloc_context();
+    if (!recorder->ctx) {
+        LOGE("Could not allocate output context");
+        goto error_cond_destroy;
+    }
+
+    // contrary to the deprecated API (av_oformat_next()), av_muxer_iterate()
+    // returns (on purpose) a pointer-to-const, but AVFormatContext.oformat
+    // still expects a pointer-to-non-const (it has not be updated accordingly)
+    // <https://github.com/FFmpeg/FFmpeg/commit/0694d8702421e7aff1340038559c438b61bb30dd>
+    recorder->ctx->oformat = (AVOutputFormat *) format;
+
+    av_dict_set(&recorder->ctx->metadata, "comment",
+                "Recorded by scrcpy " SCRCPY_VERSION, 0);
+
+    AVStream *ostream = avformat_new_stream(recorder->ctx, input_codec);
+    if (!ostream) {
+        goto error_avformat_free_context;
+    }
+
+    ostream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
+    ostream->codecpar->codec_id = input_codec->id;
+    ostream->codecpar->format = AV_PIX_FMT_YUV420P;
+    ostream->codecpar->width = recorder->declared_frame_size.width;
+    ostream->codecpar->height = recorder->declared_frame_size.height;
+
+    int ret = avio_open(&recorder->ctx->pb, recorder->filename,
+                        AVIO_FLAG_WRITE);
+    if (ret < 0) {
+        LOGE("Failed to open output file: %s", recorder->filename);
+        // ostream will be cleaned up during context cleaning
+        goto error_avformat_free_context;
+    }
+
+    LOGD("Starting recorder thread");
+    ok = sc_thread_create(&recorder->thread, run_recorder, "recorder",
+                               recorder);
+    if (!ok) {
+        LOGC("Could not start recorder thread");
+        goto error_avio_close;
+    }
+
+    LOGI("Recording started to %s file: %s", format_name, recorder->filename);
+
+    return true;
+
+error_avio_close:
+    avio_close(recorder->ctx->pb);
+error_avformat_free_context:
+    avformat_free_context(recorder->ctx);
+error_cond_destroy:
+    sc_cond_destroy(&recorder->queue_cond);
+error_mutex_destroy:
+    sc_mutex_destroy(&recorder->mutex);
+
+    return false;
+}
+
+static void
+recorder_close(struct recorder *recorder) {
     sc_mutex_lock(&recorder->mutex);
     recorder->stopped = true;
     sc_cond_signal(&recorder->queue_cond);
     sc_mutex_unlock(&recorder->mutex);
-}
 
-void
-recorder_join(struct recorder *recorder) {
     sc_thread_join(&recorder->thread, NULL);
+
+    avio_close(recorder->ctx->pb);
+    avformat_free_context(recorder->ctx);
+    sc_cond_destroy(&recorder->queue_cond);
+    sc_mutex_destroy(&recorder->mutex);
 }
 
-bool
+static bool
 recorder_push(struct recorder *recorder, const AVPacket *packet) {
     sc_mutex_lock(&recorder->mutex);
     assert(!recorder->stopped);
@@ -376,3 +342,51 @@ recorder_push(struct recorder *recorder, const AVPacket *packet) {
     sc_mutex_unlock(&recorder->mutex);
     return true;
 }
+
+static bool
+recorder_packet_sink_open(struct sc_packet_sink *sink, const AVCodec *codec) {
+    struct recorder *recorder = DOWNCAST(sink);
+    return recorder_open(recorder, codec);
+}
+
+static void
+recorder_packet_sink_close(struct sc_packet_sink *sink) {
+    struct recorder *recorder = DOWNCAST(sink);
+    recorder_close(recorder);
+}
+
+static bool
+recorder_packet_sink_push(struct sc_packet_sink *sink, const AVPacket *packet) {
+    struct recorder *recorder = DOWNCAST(sink);
+    return recorder_push(recorder, packet);
+}
+
+bool
+recorder_init(struct recorder *recorder,
+              const char *filename,
+              enum sc_record_format format,
+              struct size declared_frame_size) {
+    recorder->filename = strdup(filename);
+    if (!recorder->filename) {
+        LOGE("Could not strdup filename");
+        return false;
+    }
+
+    recorder->format = format;
+    recorder->declared_frame_size = declared_frame_size;
+
+    static const struct sc_packet_sink_ops ops = {
+        .open = recorder_packet_sink_open,
+        .close = recorder_packet_sink_close,
+        .push = recorder_packet_sink_push,
+    };
+
+    recorder->packet_sink.ops = &ops;
+
+    return true;
+}
+
+void
+recorder_destroy(struct recorder *recorder) {
+    free(recorder->filename);
+}

app/src/recorder.h

@@ -8,6 +8,7 @@
 
 #include "coords.h"
 #include "scrcpy.h"
+#include "trait/packet_sink.h"
 #include "util/queue.h"
 #include "util/thread.h"
 
@@ -19,6 +20,8 @@ struct record_packet {
 struct recorder_queue QUEUE(struct record_packet);
 
 struct recorder {
+    struct sc_packet_sink packet_sink; // packet sink trait
+
     char *filename;
     enum sc_record_format format;
     AVFormatContext *ctx;
@@ -28,7 +31,7 @@ struct recorder {
     sc_thread thread;
     sc_mutex mutex;
     sc_cond queue_cond;
-    bool stopped; // set on recorder_stop() by the stream reader
+    bool stopped; // set on recorder_close()
     bool failed; // set on packet write failure
     struct recorder_queue queue;
 
@@ -46,22 +49,4 @@ recorder_init(struct recorder *recorder, const char *filename,
 void
 recorder_destroy(struct recorder *recorder);
 
-bool
-recorder_open(struct recorder *recorder, const AVCodec *input_codec);
-
-void
-recorder_close(struct recorder *recorder);
-
-bool
-recorder_start(struct recorder *recorder);
-
-void
-recorder_stop(struct recorder *recorder);
-
-void
-recorder_join(struct recorder *recorder);
-
-bool
-recorder_push(struct recorder *recorder, const AVPacket *packet);
-
 #endif

app/src/scrcpy.c

@@ -25,17 +25,21 @@
 #include "server.h"
 #include "stream.h"
 #include "tiny_xpm.h"
-#include "video_buffer.h"
 #include "util/log.h"
 #include "util/net.h"
+#ifdef HAVE_V4L2
+# include "v4l2_sink.h"
+#endif
 
 static struct server server;
 static struct screen screen;
 static struct fps_counter fps_counter;
-static struct video_buffer video_buffer;
 static struct stream stream;
 static struct decoder decoder;
 static struct recorder recorder;
+#ifdef HAVE_V4L2
+static struct sc_v4l2_sink v4l2_sink;
+#endif
 static struct controller controller;
 static struct file_handler file_handler;
 
@@ -247,9 +251,11 @@ scrcpy(const struct scrcpy_options *options) {
 
     bool server_started = false;
     bool fps_counter_initialized = false;
-    bool video_buffer_initialized = false;
     bool file_handler_initialized = false;
     bool recorder_initialized = false;
+#ifdef HAVE_V4L2
+    bool v4l2_sink_initialized = false;
+#endif
     bool stream_started = false;
     bool controller_initialized = false;
     bool controller_started = false;
@@ -298,18 +304,12 @@ scrcpy(const struct scrcpy_options *options) {
         goto end;
     }
 
-    struct decoder *dec = NULL;
     if (options->display) {
         if (!fps_counter_init(&fps_counter)) {
             goto end;
         }
         fps_counter_initialized = true;
 
-        if (!video_buffer_init(&video_buffer, options->render_expired_frames)) {
-            goto end;
-        }
-        video_buffer_initialized = true;
-
         if (options->control) {
             if (!file_handler_init(&file_handler, server.serial,
                                    options->push_target)) {
@@ -317,8 +317,15 @@ scrcpy(const struct scrcpy_options *options) {
             }
             file_handler_initialized = true;
         }
+    }
 
-        decoder_init(&decoder, &video_buffer);
+    struct decoder *dec = NULL;
+    bool needs_decoder = options->display;
+#ifdef HAVE_V4L2
+    needs_decoder |= !!options->v4l2_device;
+#endif
+    if (needs_decoder) {
+        decoder_init(&decoder);
         dec = &decoder;
     }
 
@@ -336,7 +343,15 @@ scrcpy(const struct scrcpy_options *options) {
 
     av_log_set_callback(av_log_callback);
 
-    stream_init(&stream, server.video_socket, dec, rec);
+    stream_init(&stream, server.video_socket);
+
+    if (dec) {
+        stream_add_sink(&stream, &dec->packet_sink);
+    }
+
+    if (rec) {
+        stream_add_sink(&stream, &rec->packet_sink);
+    }
 
     if (options->display) {
         if (options->control) {
@@ -368,12 +383,13 @@ scrcpy(const struct scrcpy_options *options) {
             .fullscreen = options->fullscreen,
         };
 
-        if (!screen_init(&screen, &video_buffer, &fps_counter,
+        if (!screen_init(&screen, &fps_counter, &screen_params)) {
-                         &screen_params)) {
             goto end;
         }
         screen_initialized = true;
 
+        decoder_add_sink(&decoder, &screen.frame_sink);
+
         if (options->turn_screen_off) {
             struct control_msg msg;
             msg.type = CONTROL_MSG_TYPE_SET_SCREEN_POWER_MODE;
@@ -385,6 +401,18 @@ scrcpy(const struct scrcpy_options *options) {
         }
     }
 
+#ifdef HAVE_V4L2
+    if (options->v4l2_device) {
+        if (!sc_v4l2_sink_init(&v4l2_sink, options->v4l2_device, frame_size)) {
+            goto end;
+        }
+
+        decoder_add_sink(&decoder, &v4l2_sink.frame_sink);
+
+        v4l2_sink_initialized = true;
+    }
+#endif
+
     // now we consumed the header values, the socket receives the video stream
     // start the stream
     if (!stream_start(&stream)) {
@@ -397,12 +425,13 @@ scrcpy(const struct scrcpy_options *options) {
     ret = event_loop(options);
     LOGD("quit...");
 
+    // Close the window immediately on closing, because screen_destroy() may
+    // only be called once the stream thread is joined (it may take time)
+    screen_hide_window(&screen);
+
 end:
-    // stop stream and controller so that they don't continue once their socket
+    // The stream is not stopped explicitly, because it will stop by itself on
-    // is shutdown
+    // end-of-stream
-    if (stream_started) {
-        stream_stop(&stream);
-    }
     if (controller_started) {
         controller_stop(&controller);
     }
@@ -424,6 +453,12 @@ end:
         stream_join(&stream);
     }
 
+#ifdef HAVE_V4L2
+    if (v4l2_sink_initialized) {
+        sc_v4l2_sink_destroy(&v4l2_sink);
+    }
+#endif
+
     // Destroy the screen only after the stream is guaranteed to be finished,
     // because otherwise the screen could receive new frames after destruction
     if (screen_initialized) {
@@ -446,10 +481,6 @@ end:
         file_handler_destroy(&file_handler);
     }
 
-    if (video_buffer_initialized) {
-        video_buffer_destroy(&video_buffer);
-    }
-
     if (fps_counter_initialized) {
         fps_counter_join(&fps_counter);
         fps_counter_destroy(&fps_counter);

app/src/scrcpy.h

@@ -20,6 +20,16 @@ enum sc_record_format {
     SC_RECORD_FORMAT_MKV,
 };
 
+enum sc_lock_video_orientation {
+    SC_LOCK_VIDEO_ORIENTATION_UNLOCKED = -1,
+    // lock the current orientation when scrcpy starts
+    SC_LOCK_VIDEO_ORIENTATION_INITIAL = -2,
+    SC_LOCK_VIDEO_ORIENTATION_0 = 0,
+    SC_LOCK_VIDEO_ORIENTATION_1,
+    SC_LOCK_VIDEO_ORIENTATION_2,
+    SC_LOCK_VIDEO_ORIENTATION_3,
+};
+
 #define SC_MAX_SHORTCUT_MODS 8
 
 enum sc_shortcut_mod {
@@ -52,6 +62,7 @@ struct scrcpy_options {
     const char *render_driver;
     const char *codec_options;
     const char *encoder_name;
+    const char *v4l2_device;
     enum sc_log_level log_level;
     enum sc_record_format record_format;
     struct sc_port_range port_range;
@@ -59,7 +70,7 @@ struct scrcpy_options {
     uint16_t max_size;
     uint32_t bit_rate;
     uint16_t max_fps;
-    int8_t lock_video_orientation;
+    enum sc_lock_video_orientation lock_video_orientation;
     uint8_t rotation;
     int16_t window_x; // SC_WINDOW_POSITION_UNDEFINED for "auto"
     int16_t window_y; // SC_WINDOW_POSITION_UNDEFINED for "auto"
@@ -72,7 +83,6 @@ struct scrcpy_options {
     bool control;
     bool display;
     bool turn_screen_off;
-    bool render_expired_frames;
     bool prefer_text;
     bool window_borderless;
     bool mipmaps;
@@ -94,6 +104,7 @@ struct scrcpy_options {
     .render_driver = NULL, \
     .codec_options = NULL, \
     .encoder_name = NULL, \
+    .v4l2_device = NULL, \
     .log_level = SC_LOG_LEVEL_INFO, \
     .record_format = SC_RECORD_FORMAT_AUTO, \
     .port_range = { \
@@ -107,7 +118,7 @@ struct scrcpy_options {
     .max_size = 0, \
     .bit_rate = DEFAULT_BIT_RATE, \
     .max_fps = 0, \
-    .lock_video_orientation = -1, \
+    .lock_video_orientation = SC_LOCK_VIDEO_ORIENTATION_UNLOCKED, \
     .rotation = 0, \
     .window_x = SC_WINDOW_POSITION_UNDEFINED, \
     .window_y = SC_WINDOW_POSITION_UNDEFINED, \
@@ -120,7 +131,6 @@ struct scrcpy_options {
     .control = true, \
     .display = true, \
     .turn_screen_off = false, \
-    .render_expired_frames = false, \
     .prefer_text = false, \
     .window_borderless = false, \
     .mipmaps = true, \

app/src/screen.c

@@ -13,6 +13,8 @@
 
 #define DISPLAY_MARGINS 96
 
+#define DOWNCAST(SINK) container_of(SINK, struct screen, frame_sink)
+
 static inline struct size
 get_rotated_size(struct size size, int rotation) {
     struct size rotated_size;
@@ -191,27 +193,6 @@ screen_update_content_rect(struct screen *screen) {
     }
 }
 
-static void
-on_frame_available(struct video_buffer *vb, void *userdata) {
-    (void) vb;
-    (void) userdata;
-
-    static SDL_Event new_frame_event = {
-        .type = EVENT_NEW_FRAME,
-    };
-
-    // Post the event on the UI thread
-    SDL_PushEvent(&new_frame_event);
-}
-
-static void
-on_frame_skipped(struct video_buffer *vb, void *userdata) {
-    (void) vb;
-
-    struct screen *screen = userdata;
-    fps_counter_add_skipped_frame(screen->fps_counter);
-}
-
 static inline SDL_Texture *
 create_texture(struct screen *screen) {
     SDL_Renderer *renderer = screen->renderer;
@@ -262,11 +243,58 @@ event_watcher(void *data, SDL_Event *event) {
 }
 #endif
 
+static bool
+screen_frame_sink_open(struct sc_frame_sink *sink) {
+    struct screen *screen = DOWNCAST(sink);
+    (void) screen;
+#ifndef NDEBUG
+    screen->open = true;
+#endif
+
+    // nothing to do, the screen is already open on the main thread
+    return true;
+}
+
+static void
+screen_frame_sink_close(struct sc_frame_sink *sink) {
+    struct screen *screen = DOWNCAST(sink);
+    (void) screen;
+#ifndef NDEBUG
+    screen->open = false;
+#endif
+
+    // nothing to do, the screen lifecycle is not managed by the frame producer
+}
+
+static bool
+screen_frame_sink_push(struct sc_frame_sink *sink, const AVFrame *frame) {
+    struct screen *screen = DOWNCAST(sink);
+
+    bool previous_frame_skipped;
+    bool ok = video_buffer_push(&screen->vb, frame, &previous_frame_skipped);
+    if (!ok) {
+        return false;
+    }
+
+    if (previous_frame_skipped) {
+        fps_counter_add_skipped_frame(screen->fps_counter);
+        // The EVENT_NEW_FRAME triggered for the previous frame will consume
+        // this new frame instead
+    } else {
+        static SDL_Event new_frame_event = {
+            .type = EVENT_NEW_FRAME,
+        };
+
+        // Post the event on the UI thread
+        SDL_PushEvent(&new_frame_event);
+    }
+
+    return true;
+}
+
 bool
-screen_init(struct screen *screen, struct video_buffer *vb,
+screen_init(struct screen *screen, struct fps_counter *fps_counter,
-            struct fps_counter *fps_counter,
             const struct screen_params *params) {
-    screen->vb = vb;
     screen->fps_counter = fps_counter;
 
     screen->resize_pending = false;
@@ -274,11 +302,11 @@ screen_init(struct screen *screen, struct video_buffer *vb,
     screen->fullscreen = false;
     screen->maximized = false;
 
-    static const struct video_buffer_callbacks cbs = {
+    bool ok = video_buffer_init(&screen->vb);
-        .on_frame_available = on_frame_available,
+    if (!ok) {
-        .on_frame_skipped = on_frame_skipped,
+        LOGE("Could not initialize video buffer");
-    };
+        return false;
-    video_buffer_set_consumer_callbacks(vb, &cbs, screen);
+    }
 
     screen->frame_size = params->frame_size;
     screen->rotation = params->rotation;
@@ -324,6 +352,7 @@ screen_init(struct screen *screen, struct video_buffer *vb,
     if (!screen->renderer) {
         LOGC("Could not create renderer: %s", SDL_GetError());
         SDL_DestroyWindow(screen->window);
+        video_buffer_destroy(&screen->vb);
         return false;
     }
 
@@ -375,6 +404,17 @@ screen_init(struct screen *screen, struct video_buffer *vb,
         LOGC("Could not create texture: %s", SDL_GetError());
         SDL_DestroyRenderer(screen->renderer);
         SDL_DestroyWindow(screen->window);
+        video_buffer_destroy(&screen->vb);
+        return false;
+    }
+
+    screen->frame = av_frame_alloc();
+    if (!screen->frame) {
+        LOGC("Could not create screen frame");
+        SDL_DestroyTexture(screen->texture);
+        SDL_DestroyRenderer(screen->renderer);
+        SDL_DestroyWindow(screen->window);
+        video_buffer_destroy(&screen->vb);
         return false;
     }
 
@@ -393,6 +433,18 @@ screen_init(struct screen *screen, struct video_buffer *vb,
     SDL_AddEventWatch(event_watcher, screen);
 #endif
 
+    static const struct sc_frame_sink_ops ops = {
+        .open = screen_frame_sink_open,
+        .close = screen_frame_sink_close,
+        .push = screen_frame_sink_push,
+    };
+
+    screen->frame_sink.ops = &ops;
+
+#ifndef NDEBUG
+    screen->open = false;
+#endif
+
     return true;
 }
 
@@ -401,11 +453,21 @@ screen_show_window(struct screen *screen) {
     SDL_ShowWindow(screen->window);
 }
 
+void
+screen_hide_window(struct screen *screen) {
+    SDL_HideWindow(screen->window);
+}
+
 void
 screen_destroy(struct screen *screen) {
+#ifndef NDEBUG
+    assert(!screen->open);
+#endif
+    av_frame_free(&screen->frame);
     SDL_DestroyTexture(screen->texture);
     SDL_DestroyRenderer(screen->renderer);
     SDL_DestroyWindow(screen->window);
+    video_buffer_destroy(&screen->vb);
 }
 
 static void
@@ -510,7 +572,9 @@ update_texture(struct screen *screen, const AVFrame *frame) {
 
 static bool
 screen_update_frame(struct screen *screen) {
-    const AVFrame *frame = video_buffer_consumer_take_frame(screen->vb);
+    av_frame_unref(screen->frame);
+    video_buffer_consume(&screen->vb, screen->frame);
+    AVFrame *frame = screen->frame;
 
     fps_counter_add_rendered_frame(screen->fps_counter);
 

app/src/screen.h

@@ -9,11 +9,17 @@
 
 #include "coords.h"
 #include "opengl.h"
-
+#include "trait/frame_sink.h"
-struct video_buffer;
+#include "video_buffer.h"
 
 struct screen {
-    struct video_buffer *vb;
+    struct sc_frame_sink frame_sink; // frame sink trait
+
+#ifndef NDEBUG
+    bool open; // track the open/close state to assert correct behavior
+#endif
+
+    struct video_buffer vb;
     struct fps_counter *fps_counter;
 
     SDL_Window *window;
@@ -36,6 +42,8 @@ struct screen {
     bool fullscreen;
     bool maximized;
     bool mipmaps;
+
+    AVFrame *frame;
 };
 
 struct screen_params {
@@ -58,14 +66,20 @@ struct screen_params {
 
 // initialize screen, create window, renderer and texture (window is hidden)
 bool
-screen_init(struct screen *screen, struct video_buffer *vb,
+screen_init(struct screen *screen, struct fps_counter *fps_counter,
-            struct fps_counter *fps_counter,
             const struct screen_params *params);
 
 // destroy window, renderer and texture (if any)
 void
 screen_destroy(struct screen *screen);
 
+// hide the window
+//
+// It is used to hide the window immediately on closing without waiting for
+// screen_destroy()
+void
+screen_hide_window(struct screen *screen);
+
 // render the texture to the renderer
 //
 // Set the update_content_rect flag if the window or content size may have

app/src/stream.c

@@ -66,25 +66,11 @@ notify_stopped(void) {
 }
 
 static bool
-process_config_packet(struct stream *stream, AVPacket *packet) {
+push_packet_to_sinks(struct stream *stream, const AVPacket *packet) {
-    if (stream->recorder && !recorder_push(stream->recorder, packet)) {
+    for (unsigned i = 0; i < stream->sink_count; ++i) {
-        LOGE("Could not send config packet to recorder");
+        struct sc_packet_sink *sink = stream->sinks[i];
-        return false;
+        if (!sink->ops->push(sink, packet)) {
-    }
+            LOGE("Could not send config packet to sink %d", i);
-    return true;
-}
-
-static bool
-process_frame(struct stream *stream, AVPacket *packet) {
-    if (stream->decoder && !decoder_push(stream->decoder, packet)) {
-        return false;
-    }
-
-    if (stream->recorder) {
-        packet->dts = packet->pts;
-
-        if (!recorder_push(stream->recorder, packet)) {
-            LOGE("Could not send packet to recorder");
             return false;
         }
     }
@@ -111,9 +97,11 @@ stream_parse(struct stream *stream, AVPacket *packet) {
         packet->flags |= AV_PKT_FLAG_KEY;
     }
 
-    bool ok = process_frame(stream, packet);
+    packet->dts = packet->pts;
+
+    bool ok = push_packet_to_sinks(stream, packet);
     if (!ok) {
-        LOGE("Could not process frame");
+        LOGE("Could not process packet");
         return false;
     }
 
@@ -156,7 +144,7 @@ stream_push_packet(struct stream *stream, AVPacket *packet) {
 
     if (is_config) {
         // config packet
-        bool ok = process_config_packet(stream, packet);
+        bool ok = push_packet_to_sinks(stream, packet);
         if (!ok) {
             return false;
         }
@@ -177,6 +165,33 @@ stream_push_packet(struct stream *stream, AVPacket *packet) {
     return true;
 }
 
+static void
+stream_close_first_sinks(struct stream *stream, unsigned count) {
+    while (count) {
+        struct sc_packet_sink *sink = stream->sinks[--count];
+        sink->ops->close(sink);
+    }
+}
+
+static inline void
+stream_close_sinks(struct stream *stream) {
+    stream_close_first_sinks(stream, stream->sink_count);
+}
+
+static bool
+stream_open_sinks(struct stream *stream, const AVCodec *codec) {
+    for (unsigned i = 0; i < stream->sink_count; ++i) {
+        struct sc_packet_sink *sink = stream->sinks[i];
+        if (!sink->ops->open(sink, codec)) {
+            LOGE("Could not open packet sink %d", i);
+            stream_close_first_sinks(stream, i);
+            return false;
+        }
+    }
+
+    return true;
+}
+
 static int
 run_stream(void *data) {
     struct stream *stream = data;
@@ -193,27 +208,15 @@ run_stream(void *data) {
         goto end;
     }
 
-    if (stream->decoder && !decoder_open(stream->decoder, codec)) {
+    if (!stream_open_sinks(stream, codec)) {
-        LOGE("Could not open decoder");
+        LOGE("Could not open stream sinks");
         goto finally_free_codec_ctx;
     }
 
-    if (stream->recorder) {
-        if (!recorder_open(stream->recorder, codec)) {
-            LOGE("Could not open recorder");
-            goto finally_close_decoder;
-        }
-
-        if (!recorder_start(stream->recorder)) {
-            LOGE("Could not start recorder");
-            goto finally_close_recorder;
-        }
-    }
-
     stream->parser = av_parser_init(AV_CODEC_ID_H264);
     if (!stream->parser) {
         LOGE("Could not initialize parser");
-        goto finally_stop_and_join_recorder;
+        goto finally_close_sinks;
     }
 
     // We must only pass complete frames to av_parser_parse2()!
@@ -243,20 +246,8 @@ run_stream(void *data) {
     }
 
     av_parser_close(stream->parser);
-finally_stop_and_join_recorder:
+finally_close_sinks:
-    if (stream->recorder) {
+    stream_close_sinks(stream);
-        recorder_stop(stream->recorder);
-        LOGI("Finishing recording...");
-        recorder_join(stream->recorder);
-    }
-finally_close_recorder:
-    if (stream->recorder) {
-        recorder_close(stream->recorder);
-    }
-finally_close_decoder:
-    if (stream->decoder) {
-        decoder_close(stream->decoder);
-    }
 finally_free_codec_ctx:
     avcodec_free_context(&stream->codec_ctx);
 end:
@@ -265,12 +256,18 @@ end:
 }
 
 void
-stream_init(struct stream *stream, socket_t socket,
+stream_init(struct stream *stream, socket_t socket) {
-            struct decoder *decoder, struct recorder *recorder) {
     stream->socket = socket;
-    stream->decoder = decoder,
-    stream->recorder = recorder;
     stream->has_pending = false;
+    stream->sink_count = 0;
+}
+
+void
+stream_add_sink(struct stream *stream, struct sc_packet_sink *sink) {
+    assert(stream->sink_count < STREAM_MAX_SINKS);
+    assert(sink);
+    assert(sink->ops);
+    stream->sinks[stream->sink_count++] = sink;
 }
 
 bool
@@ -285,13 +282,6 @@ stream_start(struct stream *stream) {
     return true;
 }
 
-void
-stream_stop(struct stream *stream) {
-    if (stream->decoder) {
-        decoder_interrupt(stream->decoder);
-    }
-}
-
 void
 stream_join(struct stream *stream) {
     sc_thread_join(&stream->thread, NULL);

app/src/stream.h

@@ -8,14 +8,19 @@
 #include <libavformat/avformat.h>
 #include <SDL2/SDL_atomic.h>
 
+#include "trait/packet_sink.h"
 #include "util/net.h"
 #include "util/thread.h"
 
+#define STREAM_MAX_SINKS 2
+
 struct stream {
     socket_t socket;
     sc_thread thread;
-    struct decoder *decoder;
+
-    struct recorder *recorder;
+    struct sc_packet_sink *sinks[STREAM_MAX_SINKS];
+    unsigned sink_count;
+
     AVCodecContext *codec_ctx;
     AVCodecParserContext *parser;
     // successive packets may need to be concatenated, until a non-config
@@ -25,15 +30,14 @@ struct stream {
 };
 
 void
-stream_init(struct stream *stream, socket_t socket,
+stream_init(struct stream *stream, socket_t socket);
-            struct decoder *decoder, struct recorder *recorder);
+
+void
+stream_add_sink(struct stream *stream, struct sc_packet_sink *sink);
 
 bool
 stream_start(struct stream *stream);
 
-void
-stream_stop(struct stream *stream);
-
 void
 stream_join(struct stream *stream);
 

app/src/trait/frame_sink.h

@@ -0,0 +1,26 @@
+#ifndef SC_FRAME_SINK
+#define SC_FRAME_SINK
+
+#include "common.h"
+
+#include <assert.h>
+#include <stdbool.h>
+
+typedef struct AVFrame AVFrame;
+
+/**
+ * Frame sink trait.
+ *
+ * Component able to receive AVFrames should implement this trait.
+ */
+struct sc_frame_sink {
+    const struct sc_frame_sink_ops *ops;
+};
+
+struct sc_frame_sink_ops {
+    bool (*open)(struct sc_frame_sink *sink);
+    void (*close)(struct sc_frame_sink *sink);
+    bool (*push)(struct sc_frame_sink *sink, const AVFrame *frame);
+};
+
+#endif

app/src/trait/packet_sink.h

@@ -0,0 +1,27 @@
+#ifndef SC_PACKET_SINK
+#define SC_PACKET_SINK
+
+#include "common.h"
+
+#include <assert.h>
+#include <stdbool.h>
+
+typedef struct AVCodec AVCodec;
+typedef struct AVPacket AVPacket;
+
+/**
+ * Packet sink trait.
+ *
+ * Component able to receive AVPackets should implement this trait.
+ */
+struct sc_packet_sink {
+    const struct sc_packet_sink_ops *ops;
+};
+
+struct sc_packet_sink_ops {
+    bool (*open)(struct sc_packet_sink *sink, const AVCodec *codec);
+    void (*close)(struct sc_packet_sink *sink);
+    bool (*push)(struct sc_packet_sink *sink, const AVPacket *packet);
+};
+
+#endif

app/src/util/str_util.c

@@ -140,6 +140,24 @@ parse_integer_with_suffix(const char *s, long *out) {
     return true;
 }
 
+bool
+strlist_contains(const char *list, char sep, const char *s) {
+    char *p;
+    do {
+        p = strchr(list, sep);
+
+        size_t token_len = p ? (size_t) (p - list) : strlen(list);
+        if (!strncmp(list, s, token_len)) {
+            return true;
+        }
+
+        if (p) {
+            list = p + 1;
+        }
+    } while (p);
+    return false;
+}
+
 size_t
 utf8_truncation_index(const char *utf8, size_t max_len) {
     size_t len = strlen(utf8);

app/src/util/str_util.h

@@ -43,6 +43,11 @@ parse_integers(const char *s, const char sep, size_t max_items, long *out);
 bool
 parse_integer_with_suffix(const char *s, long *out);
 
+// search s in the list separated by sep
+// for example, strlist_contains("a,bc,def", ',', "bc") returns true
+bool
+strlist_contains(const char *list, char sep, const char *s);
+
 // return the index to truncate a UTF-8 string at a valid position
 size_t
 utf8_truncation_index(const char *utf8, size_t max_len);

app/src/v4l2_sink.c

@@ -0,0 +1,341 @@
+#include "v4l2_sink.h"
+
+#include "util/log.h"
+#include "util/str_util.h"
+
+/** Downcast frame_sink to sc_v4l2_sink */
+#define DOWNCAST(SINK) container_of(SINK, struct sc_v4l2_sink, frame_sink)
+
+static const AVRational SCRCPY_TIME_BASE = {1, 1000000}; // timestamps in us
+
+static const AVOutputFormat *
+find_muxer(const char *name) {
+#ifdef SCRCPY_LAVF_HAS_NEW_MUXER_ITERATOR_API
+    void *opaque = NULL;
+#endif
+    const AVOutputFormat *oformat = NULL;
+    do {
+#ifdef SCRCPY_LAVF_HAS_NEW_MUXER_ITERATOR_API
+        oformat = av_muxer_iterate(&opaque);
+#else
+        oformat = av_oformat_next(oformat);
+#endif
+        // until null or containing the requested name
+    } while (oformat && !strlist_contains(oformat->name, ',', name));
+    return oformat;
+}
+
+static bool
+write_header(struct sc_v4l2_sink *vs, const AVPacket *packet) {
+    AVStream *ostream = vs->format_ctx->streams[0];
+
+    uint8_t *extradata = av_malloc(packet->size * sizeof(uint8_t));
+    if (!extradata) {
+        LOGC("Could not allocate extradata");
+        return false;
+    }
+
+    // copy the first packet to the extra data
+    memcpy(extradata, packet->data, packet->size);
+
+    ostream->codecpar->extradata = extradata;
+    ostream->codecpar->extradata_size = packet->size;
+
+    int ret = avformat_write_header(vs->format_ctx, NULL);
+    if (ret < 0) {
+        LOGE("Failed to write header to %s", vs->device_name);
+        return false;
+    }
+
+    return true;
+}
+
+static void
+rescale_packet(struct sc_v4l2_sink *vs, AVPacket *packet) {
+    AVStream *ostream = vs->format_ctx->streams[0];
+    av_packet_rescale_ts(packet, SCRCPY_TIME_BASE, ostream->time_base);
+}
+
+static bool
+write_packet(struct sc_v4l2_sink *vs, AVPacket *packet) {
+    if (!vs->header_written) {
+        bool ok = write_header(vs, packet);
+        if (!ok) {
+            return false;
+        }
+        vs->header_written = true;
+        return true;
+    }
+
+    rescale_packet(vs, packet);
+
+    bool ok = av_write_frame(vs->format_ctx, packet) >= 0;
+
+    // Failing to write the last frame is not very serious, no future frame may
+    // depend on it, so the resulting file will still be valid
+    (void) ok;
+
+    return true;
+}
+
+static bool
+encode_and_write_frame(struct sc_v4l2_sink *vs, const AVFrame *frame) {
+    int ret = avcodec_send_frame(vs->encoder_ctx, frame);
+    if (ret < 0 && ret != AVERROR(EAGAIN)) {
+        LOGE("Could not send v4l2 video frame: %d", ret);
+        return false;
+    }
+
+    AVPacket *packet = &vs->packet;
+    ret = avcodec_receive_packet(vs->encoder_ctx, packet);
+    if (ret == 0) {
+        // A packet was received
+
+        bool ok = write_packet(vs, packet);
+        if (!ok) {
+            LOGW("Could not send packet to v4l2 sink");
+            return false;
+        }
+        av_packet_unref(packet);
+    } else if (ret != AVERROR(EAGAIN)) {
+        LOGE("Could not receive v4l2 video packet: %d", ret);
+        return false;
+    }
+
+    return true;
+}
+
+static int
+run_v4l2_sink(void *data) {
+    struct sc_v4l2_sink *vs = data;
+
+    for (;;) {
+        sc_mutex_lock(&vs->mutex);
+
+        while (!vs->stopped && vs->vb.pending_frame_consumed) {
+            sc_cond_wait(&vs->cond, &vs->mutex);
+        }
+
+        if (vs->stopped) {
+            sc_mutex_unlock(&vs->mutex);
+            break;
+        }
+
+        sc_mutex_unlock(&vs->mutex);
+
+        video_buffer_consume(&vs->vb, vs->frame);
+        bool ok = encode_and_write_frame(vs, vs->frame);
+        if (!ok) {
+            LOGE("Could not send frame to v4l2 sink");
+            break;
+        }
+    }
+
+    LOGD("V4l2 thread ended");
+
+    return 0;
+}
+
+static bool
+sc_v4l2_sink_open(struct sc_v4l2_sink *vs) {
+    bool ok = video_buffer_init(&vs->vb);
+    if (!ok) {
+        return false;
+    }
+
+    ok = sc_mutex_init(&vs->mutex);
+    if (!ok) {
+        LOGC("Could not create mutex");
+        goto error_video_buffer_destroy;
+    }
+
+    ok = sc_cond_init(&vs->cond);
+    if (!ok) {
+        LOGC("Could not create cond");
+        goto error_mutex_destroy;
+    }
+
+    // FIXME
+    const AVOutputFormat *format = find_muxer("video4linux2,v4l2");
+    if (!format) {
+        LOGE("Could not find v4l2 muxer");
+        goto error_cond_destroy;
+    }
+
+    const AVCodec *encoder = avcodec_find_encoder(AV_CODEC_ID_RAWVIDEO);
+    if (!encoder) {
+        LOGE("Raw video encoder not found");
+        return false;
+    }
+
+    vs->format_ctx = avformat_alloc_context();
+    if (!vs->format_ctx) {
+        LOGE("Could not allocate v4l2 output context");
+        return false;
+    }
+
+    // contrary to the deprecated API (av_oformat_next()), av_muxer_iterate()
+    // returns (on purpose) a pointer-to-const, but AVFormatContext.oformat
+    // still expects a pointer-to-non-const (it has not be updated accordingly)
+    // <https://github.com/FFmpeg/FFmpeg/commit/0694d8702421e7aff1340038559c438b61bb30dd>
+    vs->format_ctx->oformat = (AVOutputFormat *) format;
+    vs->format_ctx->url = strdup(vs->device_name);
+    if (!vs->format_ctx->url) {
+        LOGE("Could not strdup v4l2 device name");
+        goto error_avformat_free_context;
+        return false;
+    }
+
+    AVStream *ostream = avformat_new_stream(vs->format_ctx, encoder);
+    if (!ostream) {
+        LOGE("Could not allocate new v4l2 stream");
+        goto error_avformat_free_context;
+        return false;
+    }
+
+    ostream->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;
+    ostream->codecpar->codec_id = encoder->id;
+    ostream->codecpar->format = AV_PIX_FMT_YUV420P;
+    ostream->codecpar->width = vs->frame_size.width;
+    ostream->codecpar->height = vs->frame_size.height;
+
+    int ret = avio_open(&vs->format_ctx->pb, vs->device_name, AVIO_FLAG_WRITE);
+    if (ret < 0) {
+        LOGE("Failed to open output device: %s", vs->device_name);
+        // ostream will be cleaned up during context cleaning
+        goto error_avformat_free_context;
+    }
+
+    vs->encoder_ctx = avcodec_alloc_context3(encoder);
+    if (!vs->encoder_ctx) {
+        LOGC("Could not allocate codec context for v4l2");
+        goto error_avio_close;
+    }
+
+    vs->encoder_ctx->width = vs->frame_size.width;
+    vs->encoder_ctx->height = vs->frame_size.height;
+    vs->encoder_ctx->pix_fmt = AV_PIX_FMT_YUV420P;
+    vs->encoder_ctx->time_base.num = 1;
+    vs->encoder_ctx->time_base.den = 1;
+
+    if (avcodec_open2(vs->encoder_ctx, encoder, NULL) < 0) {
+        LOGE("Could not open codec for v4l2");
+        goto error_avcodec_free_context;
+    }
+
+    vs->frame = av_frame_alloc();
+    if (!vs->frame) {
+        LOGE("Could not create v4l2 frame");
+        goto error_avcodec_close;
+    }
+
+    LOGD("Starting v4l2 thread");
+    ok = sc_thread_create(&vs->thread, run_v4l2_sink, "v4l2", vs);
+    if (!ok) {
+        LOGC("Could not start v4l2 thread");
+        goto error_av_frame_free;
+    }
+
+    vs->header_written = false;
+    vs->stopped = false;
+
+    LOGI("v4l2 sink started to device: %s", vs->device_name);
+
+    return true;
+
+error_av_frame_free:
+    av_frame_free(&vs->frame);
+error_avcodec_close:
+    avcodec_close(vs->encoder_ctx);
+error_avcodec_free_context:
+    avcodec_free_context(&vs->encoder_ctx);
+error_avio_close:
+    avio_close(vs->format_ctx->pb);
+error_avformat_free_context:
+    avformat_free_context(vs->format_ctx);
+error_cond_destroy:
+    sc_cond_destroy(&vs->cond);
+error_mutex_destroy:
+    sc_mutex_destroy(&vs->mutex);
+error_video_buffer_destroy:
+    video_buffer_destroy(&vs->vb);
+
+    return false;
+}
+
+static void
+sc_v4l2_sink_close(struct sc_v4l2_sink *vs) {
+    sc_mutex_lock(&vs->mutex);
+    vs->stopped = true;
+    sc_cond_signal(&vs->cond);
+    sc_mutex_unlock(&vs->mutex);
+
+    sc_thread_join(&vs->thread, NULL);
+
+    av_frame_free(&vs->frame);
+    avcodec_close(vs->encoder_ctx);
+    avcodec_free_context(&vs->encoder_ctx);
+    avio_close(vs->format_ctx->pb);
+    avformat_free_context(vs->format_ctx);
+    sc_cond_destroy(&vs->cond);
+    sc_mutex_destroy(&vs->mutex);
+    video_buffer_destroy(&vs->vb);
+}
+
+static bool
+sc_v4l2_sink_push(struct sc_v4l2_sink *vs, const AVFrame *frame) {
+    bool ok = video_buffer_push(&vs->vb, frame, NULL);
+    if (!ok) {
+        return false;
+    }
+
+    // signal possible change of vs->vb.pending_frame_consumed
+    sc_cond_signal(&vs->cond);
+
+    return true;
+}
+
+static bool
+sc_v4l2_frame_sink_open(struct sc_frame_sink *sink) {
+    struct sc_v4l2_sink *vs = DOWNCAST(sink);
+    return sc_v4l2_sink_open(vs);
+}
+
+static void
+sc_v4l2_frame_sink_close(struct sc_frame_sink *sink) {
+    struct sc_v4l2_sink *vs = DOWNCAST(sink);
+    sc_v4l2_sink_close(vs);
+}
+
+static bool
+sc_v4l2_frame_sink_push(struct sc_frame_sink *sink, const AVFrame *frame) {
+    struct sc_v4l2_sink *vs = DOWNCAST(sink);
+    return sc_v4l2_sink_push(vs, frame);
+}
+
+bool
+sc_v4l2_sink_init(struct sc_v4l2_sink *vs, const char *device_name,
+                  struct size frame_size) {
+    vs->device_name = strdup(device_name);
+    if (!vs->device_name) {
+        LOGE("Could not strdup v4l2 device name");
+        return false;
+    }
+
+    vs->frame_size = frame_size;
+
+    static const struct sc_frame_sink_ops ops = {
+        .open = sc_v4l2_frame_sink_open,
+        .close = sc_v4l2_frame_sink_close,
+        .push = sc_v4l2_frame_sink_push,
+    };
+
+    vs->frame_sink.ops = &ops;
+
+    return true;
+}
+
+void
+sc_v4l2_sink_destroy(struct sc_v4l2_sink *vs) {
+    free(vs->device_name);
+}

app/src/v4l2_sink.h

@@ -0,0 +1,39 @@
+#ifndef SC_V4L2_SINK_H
+#define SC_V4L2_SINK_H
+
+#include "common.h"
+
+#include "coords.h"
+#include "trait/frame_sink.h"
+#include "video_buffer.h"
+
+#include <libavformat/avformat.h>
+
+struct sc_v4l2_sink {
+    struct sc_frame_sink frame_sink; // frame sink trait
+
+    struct video_buffer vb;
+    AVFormatContext *format_ctx;
+    AVCodecContext *encoder_ctx;
+
+    char *device_name;
+    struct size frame_size;
+
+    sc_thread thread;
+    sc_mutex mutex;
+    sc_cond cond;
+    bool stopped;
+    bool header_written;
+
+    AVFrame *frame;
+    AVPacket packet;
+};
+
+bool
+sc_v4l2_sink_init(struct sc_v4l2_sink *vs, const char *device_name,
+                  struct size frame_size);
+
+void
+sc_v4l2_sink_destroy(struct sc_v4l2_sink *vs);
+
+#endif

app/src/video_buffer.c

@@ -7,67 +7,36 @@
 #include "util/log.h"
 
 bool
-video_buffer_init(struct video_buffer *vb, bool wait_consumer) {
+video_buffer_init(struct video_buffer *vb) {
-    vb->producer_frame = av_frame_alloc();
-    if (!vb->producer_frame) {
-        goto error_0;
-    }
-
     vb->pending_frame = av_frame_alloc();
     if (!vb->pending_frame) {
-        goto error_1;
+        return false;
     }
 
-    vb->consumer_frame = av_frame_alloc();
+    vb->tmp_frame = av_frame_alloc();
-    if (!vb->consumer_frame) {
+    if (!vb->tmp_frame) {
-        goto error_2;
+        av_frame_free(&vb->pending_frame);
+        return false;
     }
 
     bool ok = sc_mutex_init(&vb->mutex);
     if (!ok) {
-        goto error_3;
+        av_frame_free(&vb->pending_frame);
-    }
+        av_frame_free(&vb->tmp_frame);
-
+        return false;
-    vb->wait_consumer = wait_consumer;
-    if (wait_consumer) {
-        ok = sc_cond_init(&vb->pending_frame_consumed_cond);
-        if (!ok) {
-            sc_mutex_destroy(&vb->mutex);
-            goto error_2;
-        }
-        // interrupted is not used if wait_consumer is disabled since offering
-        // a frame will never block
-        vb->interrupted = false;
     }
 
     // there is initially no frame, so consider it has already been consumed
     vb->pending_frame_consumed = true;
 
-    // The callbacks must be set by the consumer via
-    // video_buffer_set_consumer_callbacks()
-    vb->cbs = NULL;
-
     return true;
-
-error_3:
-    av_frame_free(&vb->consumer_frame);
-error_2:
-    av_frame_free(&vb->pending_frame);
-error_1:
-    av_frame_free(&vb->producer_frame);
-error_0:
-    return false;
 }
 
 void
 video_buffer_destroy(struct video_buffer *vb) {
-    if (vb->wait_consumer) {
-        sc_cond_destroy(&vb->pending_frame_consumed_cond);
-    }
     sc_mutex_destroy(&vb->mutex);
-    av_frame_free(&vb->consumer_frame);
     av_frame_free(&vb->pending_frame);
-    av_frame_free(&vb->producer_frame);
+    av_frame_free(&vb->tmp_frame);
 }
 
 static inline void
@@ -77,71 +46,43 @@ swap_frames(AVFrame **lhs, AVFrame **rhs) {
     *rhs = tmp;
 }
 
-void
+bool
-video_buffer_set_consumer_callbacks(struct video_buffer *vb,
+video_buffer_push(struct video_buffer *vb, const AVFrame *frame,
-                                    const struct video_buffer_callbacks *cbs,
+                  bool *previous_frame_skipped) {
-                                    void *cbs_userdata) {
-    assert(!vb->cbs); // must be set only once
-    assert(cbs);
-    assert(cbs->on_frame_available);
-    vb->cbs = cbs;
-    vb->cbs_userdata = cbs_userdata;
-}
-
-void
-video_buffer_producer_offer_frame(struct video_buffer *vb) {
-    assert(vb->cbs);
-
     sc_mutex_lock(&vb->mutex);
-    if (vb->wait_consumer) {
+
-        // wait for the current (expired) frame to be consumed
+    // Use a temporary frame to preserve pending_frame in case of error.
-        while (!vb->pending_frame_consumed && !vb->interrupted) {
+    // tmp_frame is an empty frame, no need to call av_frame_unref() beforehand.
-            sc_cond_wait(&vb->pending_frame_consumed_cond, &vb->mutex);
+    int r = av_frame_ref(vb->tmp_frame, frame);
-        }
+    if (r) {
+        LOGE("Could not ref frame: %d", r);
+        return false;
     }
 
-    av_frame_unref(vb->pending_frame);
+    // Now that av_frame_ref() succeeded, we can replace the previous
-    swap_frames(&vb->producer_frame, &vb->pending_frame);
+    // pending_frame
+    swap_frames(&vb->pending_frame, &vb->tmp_frame);
+    av_frame_unref(vb->tmp_frame);
 
-    bool skipped = !vb->pending_frame_consumed;
+    if (previous_frame_skipped) {
+        *previous_frame_skipped = !vb->pending_frame_consumed;
+    }
     vb->pending_frame_consumed = false;
 
     sc_mutex_unlock(&vb->mutex);
 
-    if (skipped) {
+    return true;
-        if (vb->cbs->on_frame_skipped)
-            vb->cbs->on_frame_skipped(vb, vb->cbs_userdata);
-    } else {
-        vb->cbs->on_frame_available(vb, vb->cbs_userdata);
-    }
 }
 
-const AVFrame *
+void
-video_buffer_consumer_take_frame(struct video_buffer *vb) {
+video_buffer_consume(struct video_buffer *vb, AVFrame *dst) {
     sc_mutex_lock(&vb->mutex);
     assert(!vb->pending_frame_consumed);
     vb->pending_frame_consumed = true;
 
-    swap_frames(&vb->consumer_frame, &vb->pending_frame);
+    av_frame_move_ref(dst, vb->pending_frame);
-    av_frame_unref(vb->pending_frame);
+    // av_frame_move_ref() resets its source frame, so no need to call
+    // av_frame_unref()
 
-    if (vb->wait_consumer) {
-        // unblock video_buffer_offer_decoded_frame()
-        sc_cond_signal(&vb->pending_frame_consumed_cond);
-    }
     sc_mutex_unlock(&vb->mutex);
-
-    // consumer_frame is only written from this thread, no need to lock
-    return vb->consumer_frame;
-}
-
-void
-video_buffer_interrupt(struct video_buffer *vb) {
-    if (vb->wait_consumer) {
-        sc_mutex_lock(&vb->mutex);
-        vb->interrupted = true;
-        sc_mutex_unlock(&vb->mutex);
-        // wake up blocking wait
-        sc_cond_signal(&vb->pending_frame_consumed_cond);
-    }
 }

app/src/video_buffer.h

@@ -12,71 +12,39 @@
 typedef struct AVFrame AVFrame;
 
 /**
- * There are 3 frames in memory:
+ * A video buffer holds 1 pending frame, which is the last frame received from
- *  - one frame is held by the producer (producer_frame)
+ * the producer (typically, the decoder).
- *  - one frame is held by the consumer (consumer_frame)
- *  - one frame is shared between the producer and the consumer (pending_frame)
  *
- * The producer generates a frame into the producer_frame (it may takes time).
+ * If a pending frame has not been consumed when the producer pushes a new
+ * frame, then it is lost. The intent is to always provide access to the very
+ * last frame to minimize latency.
  *
- * Once the frame is produced, it calls video_buffer_producer_offer_frame(),
+ * The producer and the consumer typically do not live in the same thread.
- * which swaps the producer and pending frames.
+ * That's the reason why the callback on_frame_available() does not provide the
- *
+ * frame as parameter: the consumer might post an event to its own thread to
- * When the consumer is notified that a new frame is available, it calls
+ * retrieve the pending frame from there, and that frame may have changed since
- * video_buffer_consumer_take_frame() to retrieve it, which swaps the pending
+ * the callback if producer pushed a new one in between.
- * and consumer frames. The frame is valid until the next call, without
- * blocking the producer.
  */
 
 struct video_buffer {
-    AVFrame *producer_frame;
     AVFrame *pending_frame;
-    AVFrame *consumer_frame;
+    AVFrame *tmp_frame; // To preserve the pending frame on error
 
     sc_mutex mutex;
-    bool wait_consumer; // never overwrite a pending frame if it is not consumed
-    bool interrupted;
 
-    sc_cond pending_frame_consumed_cond;
     bool pending_frame_consumed;
-
-    const struct video_buffer_callbacks *cbs;
-    void *cbs_userdata;
-};
-
-struct video_buffer_callbacks {
-    // Called when a new frame can be consumed by
-    // video_buffer_consumer_take_frame(vb)
-    // This callback is mandatory (it must not be NULL).
-    void (*on_frame_available)(struct video_buffer *vb, void *userdata);
-
-    // Called when a pending frame has been overwritten by the producer
-    // This callback is optional (it may be NULL).
-    void (*on_frame_skipped)(struct video_buffer *vb, void *userdata);
 };
 
 bool
-video_buffer_init(struct video_buffer *vb, bool wait_consumer);
+video_buffer_init(struct video_buffer *vb);
 
 void
 video_buffer_destroy(struct video_buffer *vb);
 
-void
+bool
-video_buffer_set_consumer_callbacks(struct video_buffer *vb,
+video_buffer_push(struct video_buffer *vb, const AVFrame *frame, bool *skipped);
-                                    const struct video_buffer_callbacks *cbs,
-                                    void *cbs_userdata);
 
-// set the producer frame as ready for consuming
 void
-video_buffer_producer_offer_frame(struct video_buffer *vb);
+video_buffer_consume(struct video_buffer *vb, AVFrame *dst);
-
-// mark the consumer frame as consumed and return it
-// the frame is valid until the next call to this function
-const AVFrame *
-video_buffer_consumer_take_frame(struct video_buffer *vb);
-
-// wake up and avoid any blocking call
-void
-video_buffer_interrupt(struct video_buffer *vb);
 
 #endif

app/tests/test_cli.c

@@ -58,7 +58,6 @@ static void test_options(void) {
         "--push-target", "/sdcard/Movies",
         "--record", "file",
         "--record-format", "mkv",
-        "--render-expired-frames",
         "--serial", "0123456789abcdef",
         "--show-touches",
         "--turn-screen-off",
@@ -87,7 +86,6 @@ static void test_options(void) {
     assert(!strcmp(opts->push_target, "/sdcard/Movies"));
     assert(!strcmp(opts->record_filename, "file"));
     assert(opts->record_format == SC_RECORD_FORMAT_MKV);
-    assert(opts->render_expired_frames);
     assert(!strcmp(opts->serial, "0123456789abcdef"));
     assert(opts->show_touches);
     assert(opts->turn_screen_off);

app/tests/test_strutil.c

@@ -287,6 +287,18 @@ static void test_parse_integer_with_suffix(void) {
     assert(!ok);
 }
 
+static void test_strlist_contains(void) {
+    assert(strlist_contains("a,bc,def", ',', "bc"));
+    assert(!strlist_contains("a,bc,def", ',', "b"));
+    assert(strlist_contains("", ',', ""));
+    assert(strlist_contains("abc,", ',', ""));
+    assert(strlist_contains(",abc", ',', ""));
+    assert(strlist_contains("abc,,def", ',', ""));
+    assert(!strlist_contains("abc", ',', ""));
+    assert(strlist_contains(",,|x", '|', ",,"));
+    assert(strlist_contains("xyz", '\0', "xyz"));
+}
+
 int main(int argc, char *argv[]) {
     (void) argc;
     (void) argv;
@@ -304,5 +316,6 @@ int main(int argc, char *argv[]) {
     test_parse_integer();
     test_parse_integers();
     test_parse_integer_with_suffix();
+    test_strlist_contains();
     return 0;
 }

server/src/main/java/com/genymobile/scrcpy/Device.java

@@ -25,6 +25,9 @@ public final class Device {
     public static final int POWER_MODE_OFF = SurfaceControl.POWER_MODE_OFF;
     public static final int POWER_MODE_NORMAL = SurfaceControl.POWER_MODE_NORMAL;
 
+    public static final int LOCK_VIDEO_ORIENTATION_UNLOCKED = -1;
+    public static final int LOCK_VIDEO_ORIENTATION_INITIAL = -2;
+
     private static final ServiceManager SERVICE_MANAGER = new ServiceManager();
 
     public interface RotationListener {

server/src/main/java/com/genymobile/scrcpy/ScreenInfo.java

@@ -82,6 +82,12 @@ public final class ScreenInfo {
 
     public static ScreenInfo computeScreenInfo(DisplayInfo displayInfo, Rect crop, int maxSize, int lockedVideoOrientation) {
         int rotation = displayInfo.getRotation();
+
+        if (lockedVideoOrientation == Device.LOCK_VIDEO_ORIENTATION_INITIAL) {
+            // The user requested to lock the video orientation to the current orientation
+            lockedVideoOrientation = rotation;
+        }
+
         Size deviceSize = displayInfo.getSize();
         Rect contentRect = new Rect(0, 0, deviceSize.getWidth(), deviceSize.getHeight());
         if (crop != null) {