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demux_lavf: add simple seek-by-bytes mode for MPEG

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Seeking in MPEG files with pts resets could fail completely, as it was
always done by timestamps and those of course don't unambiguously
specify a file position in such files. Add basic functionality for
byte-based seeking and playback position reporting, and decide whether
to use that functionality based on a simple heuristic (could be
improved).
This commit is contained in:
Uoti Urpala 2010-11-10 07:17:51 +02:00
parent 3c2cfee488
commit 8fb91511b1
1 changed files with 39 additions and 3 deletions
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42
libmpdemux/demux_lavf.c
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@ -77,6 +77,8 @@ typedef struct lavf_priv {
int nb_streams_last; int nb_streams_last;
bool internet_radio_hack; bool internet_radio_hack;
bool use_dts; bool use_dts;
bool seek_by_bytes;
int bitrate;
}lavf_priv_t; }lavf_priv_t;
static int mp_read(void *opaque, uint8_t *buf, int size) { static int mp_read(void *opaque, uint8_t *buf, int size) {
@ -612,7 +614,22 @@ static demuxer_t* demux_open_lavf(demuxer_t *demuxer){
demuxer->video->id=-2; // audio-only demuxer->video->id=-2; // audio-only
} //else if (best_video > 0 && demuxer->video->id == -1) demuxer->video->id = best_video; } //else if (best_video > 0 && demuxer->video->id == -1) demuxer->video->id = best_video;
demuxer->accurate_seek = true; /* libavformat sets bitrate for mpeg based on pts at start and end
* of file, which fails for files with pts resets. So calculate our
* own bitrate estimate. */
if (priv->avif->flags & AVFMT_TS_DISCONT) {
for (int i = 0; i < avfc->nb_streams; i++)
priv->bitrate += avfc->streams[i]->codec->bit_rate;
/* pts-based is more accurate if there are no resets; try to make
* a somewhat reasonable guess */
if (!avfc->duration || avfc->duration == AV_NOPTS_VALUE
|| priv->bitrate && (avfc->bit_rate < priv->bitrate / 2
|| avfc->bit_rate > priv->bitrate * 2))
priv->seek_by_bytes = true;
if (!priv->bitrate)
priv->bitrate = 1440000;
}
demuxer->accurate_seek = !priv->seek_by_bytes;
return demuxer; return demuxer;
} }
@ -751,6 +768,14 @@ static void demux_seek_lavf(demuxer_t *demuxer, float rel_seek_secs, float audio
int avsflags = 0; int avsflags = 0;
mp_msg(MSGT_DEMUX,MSGL_DBG2,"demux_seek_lavf(%p, %f, %f, %d)\n", demuxer, rel_seek_secs, audio_delay, flags); mp_msg(MSGT_DEMUX,MSGL_DBG2,"demux_seek_lavf(%p, %f, %f, %d)\n", demuxer, rel_seek_secs, audio_delay, flags);
if (priv->seek_by_bytes) {
int64_t pos = demuxer->filepos;
rel_seek_secs *= priv->bitrate / 8;
pos += rel_seek_secs;
av_seek_frame(priv->avfc, -1, pos, AVSEEK_FLAG_BYTE);
return;
}
if (flags & SEEK_ABSOLUTE) { if (flags & SEEK_ABSOLUTE) {
priv->last_pts = 0; priv->last_pts = 0;
} else { } else {
@ -780,14 +805,25 @@ static int demux_lavf_control(demuxer_t *demuxer, int cmd, void *arg)
switch (cmd) { switch (cmd) {
case DEMUXER_CTRL_CORRECT_PTS: case DEMUXER_CTRL_CORRECT_PTS:
return DEMUXER_CTRL_OK; return DEMUXER_CTRL_OK;
case DEMUXER_CTRL_GET_TIME_LENGTH: case DEMUXER_CTRL_GET_TIME_LENGTH:
if (priv->seek_by_bytes) {
/* Our bitrate estimate may be better than would be used in
* otherwise similar fallback code at higher level */
if (demuxer->movi_end <= 0)
return DEMUXER_CTRL_DONTKNOW;
*(double *)arg = (demuxer->movi_end - demuxer->movi_start) * 8 /
priv->bitrate;
return DEMUXER_CTRL_GUESS;
}
if (priv->avfc->duration == 0 || priv->avfc->duration == AV_NOPTS_VALUE) if (priv->avfc->duration == 0 || priv->avfc->duration == AV_NOPTS_VALUE)
return DEMUXER_CTRL_DONTKNOW; return DEMUXER_CTRL_DONTKNOW;
*((double *)arg) = (double)priv->avfc->duration / AV_TIME_BASE; *((double *)arg) = (double)priv->avfc->duration / AV_TIME_BASE;
return DEMUXER_CTRL_OK; return DEMUXER_CTRL_OK;
case DEMUXER_CTRL_GET_PERCENT_POS: case DEMUXER_CTRL_GET_PERCENT_POS:
if (priv->seek_by_bytes)
return DEMUXER_CTRL_DONTKNOW; // let it use the fallback code
if (priv->avfc->duration == 0 || priv->avfc->duration == AV_NOPTS_VALUE) if (priv->avfc->duration == 0 || priv->avfc->duration == AV_NOPTS_VALUE)
return DEMUXER_CTRL_DONTKNOW; return DEMUXER_CTRL_DONTKNOW;