drgreen/android_frameworks_base
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Proper chunk size computation for Layer II/III V2 and V2.5, skip optional ID3 tag.

Browse Source 
related-to-bug: 1986192
This commit is contained in:
Andreas Huber
2009-10-12 15:48:51 -07:00
parent ef703f60d5
commit 63f20ec1a8
1 changed files with 33 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

32
media/libstagefright/MP3Extractor.cpp
View File

@ -147,7 +147,12 @@ static bool get_mp3_frame_size(
*out_bitrate = bitrate;
}
if (version == 3 /* V1 */) {
*frame_size = 144000 * bitrate / sampling_rate + padding;
} else {
// V2 or V2.5
*frame_size = 72000 * bitrate / sampling_rate + padding;
}
}
if (out_sampling_rate) {
@ -166,6 +171,33 @@ static bool get_mp3_frame_size(
static bool Resync(
const sp<DataSource> &source, uint32_t match_header,
off_t *inout_pos, uint32_t *out_header) {
if (*inout_pos == 0) {
// Skip an optional ID3 header if syncing at the very beginning
// of the datasource.
uint8_t id3header[10];
if (source->read_at(0, id3header, sizeof(id3header))
< (ssize_t)sizeof(id3header)) {
// If we can't even read these 10 bytes, we might as well bail out,
// even if there _were_ 10 bytes of valid mp3 audio data...
return false;
}
if (id3header[0] == 'I' && id3header[1] == 'D' && id3header[2] == '3') {
// Skip the ID3v2 header.
size_t len =
((id3header[6] & 0x7f) << 21)
| ((id3header[7] & 0x7f) << 14)
| ((id3header[8] & 0x7f) << 7)
| (id3header[9] & 0x7f);
len += 10;
*inout_pos += len;
}
}
// Everything must match except for
// protection, bitrate, padding, private bits and mode extension.
const uint32_t kMask = 0xfffe0ccf;