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Fix for demuxers that can't seek to 0 (FFmpeg bugs, see init_seek)

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This commit is contained in:
bnnm 2016-12-01 20:11:17 +01:00
parent f5da8281e2
commit 47be992b4b
1 changed files with 57 additions and 0 deletions
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57
src/meta/ffmpeg.c
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@ -6,6 +6,9 @@
#define FFMPEG_DEFAULT_BLOCK_SIZE 2048
static void init_seek(ffmpeg_codec_data * data);
static volatile int g_ffmpeg_initialized = 0;
/*
@ -328,6 +331,11 @@ ffmpeg_codec_data * init_ffmpeg_faux_riff(STREAMFILE *streamFile, int64_t fmt_of
if (!data->sampleBuffer)
goto fail;
/* setup decent seeking for faulty formats */
init_seek(data);
return data;
fail:
@ -337,6 +345,55 @@ fail:
}
/**
* Special patching for FFmpeg's buggy seek code.
*
* To seek with avformat_seek_file/av_seek_frame, FFmpeg's demuxers can implement read_seek2 (newest API)
* or read_seek (older API), with various search modes. If none are available it will use seek_frame_generic,
* which manually reads frame by frame until the selected timestamp. However, the prev frame will be consumed
* (so after seeking to 0 next av_read_frame will actually give the second frame and so on).
*
* Fortunately seek_frame_generic can use an index to find the correct position. This function reads the
* first frame/packet and sets up index to timestamp 0. This ensures faulty demuxers will seek to 0 correctly.
*/
static void init_seek(ffmpeg_codec_data * data) {
int ret, found = 0;
int64_t ts = 0;
AVStream * stream;
AVPacket * pkt;
/* read_seek wouldn't use the index, but direct access to FFmpeg's internals is no good */
/* if (data->formatCtx->iformat->read_seek || data->formatCtx->iformat->read_seek2)
return; */
pkt = data->lastReadPacket;
/* find the first packet */
while (!found) {
av_packet_unref(pkt);
ret = av_read_frame(data->formatCtx, pkt);
if (ret < 0)
break;
if (pkt->stream_index != data->streamIndex)
continue; /* ignore non-selected streams */
found = 1;
}
if (!found)
return;
/* add index 0 */
stream = data->formatCtx->streams[data->streamIndex];
av_add_index_entry(stream, pkt->pos, ts, pkt->size, 0, AVINDEX_KEYFRAME); /* todo distance*/
/* move back to beginning, since we just consumed packets */
avformat_seek_file(data->formatCtx, data->streamIndex, ts, ts, ts, AVSEEK_FLAG_ANY);
avcodec_flush_buffers(data->codecCtx);
}
void free_ffmpeg(ffmpeg_codec_data *data) {
if (data->lastReadPacket) {
av_packet_unref(data->lastReadPacket);