Hide the window immediately on close

The screen may not be destroyed immediately on close to avoid undefined
behavior, because it may still receive events from the decoder.

But the visual window must still be closed immediately.

README.md

@@ -491,18 +491,6 @@ 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/scrcpy.1

@@ -155,10 +155,6 @@ 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.

app/src/cli.c

@@ -143,12 +143,6 @@ 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"
@@ -816,7 +810,8 @@ 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;

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
-decoder_init(struct decoder *decoder, struct video_buffer *vb) {
-    decoder->video_buffer = vb;
+/** Downcast packet_sink to decoder */
+#define DOWNCAST(SINK) container_of(SINK, struct decoder, packet_sink)
+
+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 +51,105 @@ 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 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:
-// <http://git.videolan.org/?p=ffmpeg.git;a=commitdiff;h=7fc329e2dd6226dfecaa4a1d7adf353bf2773726>
-#ifdef SCRCPY_LAVF_HAS_NEW_ENCODING_DECODING_API
+    bool is_config = packet->pts == AV_NOPTS_VALUE;
+    if (is_config) {
+        // nothing to do
+        return true;
+    }
+
     int ret;
     if ((ret = avcodec_send_packet(decoder->codec_ctx, packet)) < 0) {
         LOGE("Could not send video packet: %d", ret);
         return false;
     }
-    ret = avcodec_receive_frame(decoder->codec_ctx,
-                                decoder->video_buffer->producer_frame);
+    ret = avcodec_receive_frame(decoder->codec_ctx, decoder->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
-decoder_interrupt(struct decoder *decoder) {
-    video_buffer_interrupt(decoder->video_buffer);
+static bool
+decoder_packet_sink_open(struct sc_packet_sink *sink, const AVCodec *codec) {
+    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 1
 
 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);
-
-bool
-decoder_open(struct decoder *decoder, const AVCodec *codec);
+decoder_init(struct decoder *decoder);
 
 void
-decoder_close(struct decoder *decoder);
-
-bool
-decoder_push(struct decoder *decoder, const AVPacket *packet);
-
-void
-decoder_interrupt(struct decoder *decoder);
+decoder_add_sink(struct decoder *decoder, struct sc_frame_sink *sink);
 
 #endif

app/src/recorder.c

@@ -5,6 +5,9 @@
 
 #include "util/log.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
 
 static const AVOutputFormat *
@@ -57,50 +60,6 @@ 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 +69,6 @@ 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 +82,8 @@ 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 +189,26 @@ 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 +216,80 @@ run_recorder(void *data) {
     return 0;
 }
 
-bool
-recorder_start(struct recorder *recorder) {
-    LOGD("Starting recorder thread");
+static 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;
+    }
+
+    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
+        avformat_free_context(recorder->ctx);
+        return false;
+    }
+
+    LOGD("Starting recorder thread");
     bool ok = sc_thread_create(&recorder->thread, run_recorder, "recorder",
                                recorder);
     if (!ok) {
         LOGC("Could not start recorder thread");
+        avformat_free_context(recorder->ctx);
         return false;
     }
 
+    LOGI("Recording started to %s file: %s", format_name, recorder->filename);
+
     return true;
 }
 
-void
-recorder_stop(struct recorder *recorder) {
+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);
 }
 
-bool
+static bool
 recorder_push(struct recorder *recorder, const AVPacket *packet) {
     sc_mutex_lock(&recorder->mutex);
     assert(!recorder->stopped);
@@ -376,3 +313,73 @@ 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;
+    }
+
+    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;
+
+    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) {
+    sc_cond_destroy(&recorder->queue_cond);
+    sc_mutex_destroy(&recorder->mutex);
+    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

@@ -25,14 +25,12 @@
 #include "server.h"
 #include "stream.h"
 #include "tiny_xpm.h"
-#include "video_buffer.h"
 #include "util/log.h"
 #include "util/net.h"
 
 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;
@@ -247,7 +245,6 @@ 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;
     bool stream_started = false;
@@ -305,11 +302,6 @@ scrcpy(const struct scrcpy_options *options) {
         }
         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)) {
@@ -318,7 +310,7 @@ scrcpy(const struct scrcpy_options *options) {
             file_handler_initialized = true;
         }
 
-        decoder_init(&decoder, &video_buffer);
+        decoder_init(&decoder);
         dec = &decoder;
     }
 
@@ -336,7 +328,15 @@ 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 +368,13 @@ scrcpy(const struct scrcpy_options *options) {
             .fullscreen = options->fullscreen,
         };
 
-        if (!screen_init(&screen, &video_buffer, &fps_counter,
-                         &screen_params)) {
+        if (!screen_init(&screen, &fps_counter, &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;
@@ -397,12 +398,13 @@ 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
-    // is shutdown
-    if (stream_started) {
-        stream_stop(&stream);
-    }
+    // The stream is not stopped explicitly, because it will stop by itself on
+    // end-of-stream
     if (controller_started) {
         controller_stop(&controller);
     }
@@ -446,10 +448,6 @@ 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

@@ -72,7 +72,6 @@ struct scrcpy_options {
     bool control;
     bool display;
     bool turn_screen_off;
-    bool render_expired_frames;
     bool prefer_text;
     bool window_borderless;
     bool mipmaps;
@@ -120,7 +119,6 @@ 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,
-            struct fps_counter *fps_counter,
+screen_init(struct screen *screen, 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 = {
-        .on_frame_available = on_frame_available,
-        .on_frame_skipped = on_frame_skipped,
-    };
-    video_buffer_set_consumer_callbacks(vb, &cbs, screen);
+    bool ok = video_buffer_init(&screen->vb);
+    if (!ok) {
+        LOGE("Could not initialize video buffer");
+        return false;
+    }
 
     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 +9,19 @@
 
 #include "coords.h"
 #include "opengl.h"
+#include "trait/frame_sink.h"
+#include "video_buffer.h"
 
 struct video_buffer;
 
 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 +44,8 @@ struct screen {
     bool fullscreen;
     bool maximized;
     bool mipmaps;
+
+    AVFrame *frame;
 };
 
 struct screen_params {
@@ -58,14 +68,20 @@ struct screen_params {
 
 // initialize screen, create window, renderer and texture (window is hidden)
 bool
-screen_init(struct screen *screen, struct video_buffer *vb,
-            struct fps_counter *fps_counter,
+screen_init(struct screen *screen, 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) {
-    if (stream->recorder && !recorder_push(stream->recorder, packet)) {
-        LOGE("Could not send config packet to recorder");
-        return false;
-    }
-    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");
+push_packet_to_sinks(struct stream *stream, const AVPacket *packet) {
+    for (unsigned i = 0; i < stream->sink_count; ++i) {
+        struct sc_packet_sink *sink = stream->sinks[i];
+        if (!sink->ops->push(sink, packet)) {
+            LOGE("Could not send config packet to sink %d", i);
             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)) {
-        LOGE("Could not open decoder");
+    if (!stream_open_sinks(stream, codec)) {
+        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:
-    if (stream->recorder) {
-        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_close_sinks:
+    stream_close_sinks(stream);
 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,
-            struct decoder *decoder, struct recorder *recorder) {
+stream_init(struct stream *stream, socket_t socket) {
     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,
-            struct decoder *decoder, struct recorder *recorder);
+stream_init(struct stream *stream, socket_t socket);
+
+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 +1,24 @@
+#ifndef SC_FRAME_SINK
+#define SC_FRAME_SINK
+
+#include "common.h"
+
+#include <assert.h>
+#include <stdbool.h>
+
+/**
+ * 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 +1,25 @@
+#ifndef SC_PACKET_SINK
+#define SC_PACKET_SINK
+
+#include "common.h"
+
+#include <assert.h>
+#include <stdbool.h>
+#include <libavcodec/avcodec.h>
+
+/**
+ * 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/video_buffer.c

@@ -7,67 +7,36 @@
 #include "util/log.h"
 
 bool
-video_buffer_init(struct video_buffer *vb, bool wait_consumer) {
-    vb->producer_frame = av_frame_alloc();
-    if (!vb->producer_frame) {
-        goto error_0;
-    }
-
+video_buffer_init(struct video_buffer *vb) {
     vb->pending_frame = av_frame_alloc();
     if (!vb->pending_frame) {
-        goto error_1;
+        return false;
     }
 
-    vb->consumer_frame = av_frame_alloc();
-    if (!vb->consumer_frame) {
-        goto error_2;
+    vb->tmp_frame = av_frame_alloc();
+    if (!vb->tmp_frame) {
+        av_frame_free(&vb->pending_frame);
+        return false;
     }
 
     bool ok = sc_mutex_init(&vb->mutex);
     if (!ok) {
-        goto error_3;
-    }
-
-    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;
+        av_frame_free(&vb->pending_frame);
+        av_frame_free(&vb->tmp_frame);
+        return 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
-video_buffer_set_consumer_callbacks(struct video_buffer *vb,
-                                    const struct video_buffer_callbacks *cbs,
-                                    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);
-
+bool
+video_buffer_push(struct video_buffer *vb, const AVFrame *frame,
+                  bool *previous_frame_skipped) {
     sc_mutex_lock(&vb->mutex);
-    if (vb->wait_consumer) {
-        // wait for the current (expired) frame to be consumed
-        while (!vb->pending_frame_consumed && !vb->interrupted) {
-            sc_cond_wait(&vb->pending_frame_consumed_cond, &vb->mutex);
-        }
+
+    // Use a temporary frame to preserve pending_frame in case of error.
+    // tmp_frame is an empty frame, no need to call av_frame_unref() beforehand.
+    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);
-    swap_frames(&vb->producer_frame, &vb->pending_frame);
+    // Now that av_frame_ref() succeeded, we can replace the previous
+    // 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) {
-        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);
-    }
+    return true;
 }
 
-const AVFrame *
-video_buffer_consumer_take_frame(struct video_buffer *vb) {
+void
+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_unref(vb->pending_frame);
+    av_frame_move_ref(dst, 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:
- *  - one frame is held by the producer (producer_frame)
- *  - one frame is held by the consumer (consumer_frame)
- *  - one frame is shared between the producer and the consumer (pending_frame)
+ * A video buffer holds 1 pending frame, which is the last frame received from
+ * the producer (typically, the decoder).
  *
- * 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(),
- * which swaps the producer and pending frames.
- *
- * When the consumer is notified that a new frame is available, it calls
- * video_buffer_consumer_take_frame() to retrieve it, which swaps the pending
- * and consumer frames. The frame is valid until the next call, without
- * blocking the producer.
+ * The producer and the consumer typically do not live in the same thread.
+ * 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
+ * retrieve the pending frame from there, and that frame may have changed since
+ * the callback if producer pushed a new one in between.
  */
 
 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
-video_buffer_set_consumer_callbacks(struct video_buffer *vb,
-                                    const struct video_buffer_callbacks *cbs,
-                                    void *cbs_userdata);
+bool
+video_buffer_push(struct video_buffer *vb, const AVFrame *frame, bool *skipped);
 
-// set the producer frame as ready for consuming
 void
-video_buffer_producer_offer_frame(struct video_buffer *vb);
-
-// 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);
+video_buffer_consume(struct video_buffer *vb, AVFrame *dst);
 
 #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);