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commit de6bcf5c05e3534ee7874a2ec8c0fc5af527137b Author: Niklas Haas <[email protected]> AuthorDate: Sun Jun 28 14:48:19 2026 +0200 Commit: Niklas Haas <[email protected]> CommitDate: Mon Jun 29 09:46:36 2026 +0000 fftools/ffmpeg_demux: only throttle readrate on the slowest stream If streams are badly interleaved, then the readrate logic can end up accumulating an ever-growing lag. Rather than looping over each stream and sleeping for each stream individually based on the local DTS and lag logic, pull the sleep out of the loop and only sleep once based on the furthest-behind stream (i.e. the stream contributing the lowest sleep duration). To reproduce: $ ./ffmpeg -re -i fallbeatcaptiontest.mp4 -c copy -f null -t 10 - Before this commit, this would run at ~0.7x and accumulate an infinitely growing lag in one stream. After this commit, both streams run at ~1x as expected, after an initial burst period due to the bad (1s granularity) interleaving. Signed-off-by: Niklas Haas <[email protected]> --- fftools/ffmpeg_demux.c | 76 ++++++++++++++++++++++++++++++-------------------- 1 file changed, 45 insertions(+), 31 deletions(-) diff --git a/fftools/ffmpeg_demux.c b/fftools/ffmpeg_demux.c index 5dbd14dc0a..38bd580bfc 100644 --- a/fftools/ffmpeg_demux.c +++ b/fftools/ffmpeg_demux.c @@ -99,12 +99,6 @@ typedef struct DemuxStream { uint64_t nb_packets; // combined size of all the packets read uint64_t data_size; - // latest wallclock time at which packet reading resumed after a stall - used for readrate - int64_t resume_wc; - // timestamp of first packet sent after the latest stall - used for readrate - int64_t resume_pts; - // measure of how far behind packet reading is against spceified readrate - int64_t lag; } DemuxStream; typedef struct DemuxStreamGroup { @@ -147,6 +141,13 @@ typedef struct Demuxer { double readrate_initial_burst; float readrate_catchup; + // latest wallclock time at which packet reading resumed after a stall - used for readrate + int64_t resume_wc; + // relative timestamp of first packet sent after the latest stall - used for readrate + int64_t resume_progress; + // measure of how far behind packet reading is against spceified readrate + int64_t lag; + Scheduler *sch; AVPacket *pkt_heartbeat; @@ -517,42 +518,55 @@ static void readrate_sleep(Demuxer *d) int64_t initial_burst = AV_TIME_BASE * d->readrate_initial_burst; int resume_warn = 0; + DemuxStream *slowest = NULL; + int64_t progress = INT64_MAX; + for (int i = 0; i < f->nb_streams; i++) { InputStream *ist = f->streams[i]; DemuxStream *ds = ds_from_ist(ist); - int64_t stream_ts_offset, pts, now, wc_elapsed, lag, max_pts, limit_pts; + int64_t stream_ts_offset, pts, pts_diff; if (ds->discard || ds->finished || ds->first_dts == AV_NOPTS_VALUE) continue; stream_ts_offset = FFMAX(ds->first_dts, file_start); pts = av_rescale(ds->dts, 1000000, AV_TIME_BASE); - now = av_gettime_relative(); - wc_elapsed = now - d->wallclock_start; - - if (pts <= stream_ts_offset + initial_burst) continue; - - max_pts = stream_ts_offset + initial_burst + (int64_t)(wc_elapsed * d->readrate); - lag = FFMAX(max_pts - pts, 0); - if ( (!ds->lag && lag > 0.3 * AV_TIME_BASE) || ( lag > ds->lag + 0.3 * AV_TIME_BASE) ) { - ds->lag = lag; - ds->resume_wc = now; - ds->resume_pts = pts; - av_log_once(ds, AV_LOG_WARNING, AV_LOG_DEBUG, &resume_warn, - "Resumed reading at pts %0.3f with rate %0.3f after a lag of %0.3fs\n", - (float)pts/AV_TIME_BASE, d->readrate_catchup, (float)lag/AV_TIME_BASE); - } - if (ds->lag && !lag) - ds->lag = ds->resume_wc = ds->resume_pts = 0; - if (ds->resume_wc) { - int64_t elapsed = now - ds->resume_wc; - limit_pts = ds->resume_pts + (int64_t)(elapsed * d->readrate_catchup); - } else { - limit_pts = max_pts; + pts_diff = pts - stream_ts_offset; + if (pts_diff < progress) { + progress = pts_diff; + slowest = ds; } + } + + if (!slowest || progress <= initial_burst) + return; - if (pts > limit_pts) - av_usleep(pts - limit_pts); + int64_t now = av_gettime_relative(); + int64_t wc_elapsed = now - d->wallclock_start; + int64_t max_prog = initial_burst + (int64_t)(wc_elapsed * d->readrate); + int64_t lag = FFMAX(max_prog - progress, 0); + int64_t limit; + + if ( (!d->lag && lag > 0.3 * AV_TIME_BASE) || ( lag > d->lag + 0.3 * AV_TIME_BASE) ) { + d->lag = lag; + d->resume_wc = now; + d->resume_progress = progress; + + int64_t pts = FFMAX(slowest->first_dts, file_start) + progress; + av_log_once(slowest, AV_LOG_WARNING, AV_LOG_DEBUG, &resume_warn, + "Resumed reading at pts %0.3f with rate %0.3f after a lag of %0.3fs\n", + (float)pts/AV_TIME_BASE, d->readrate_catchup, (float)lag/AV_TIME_BASE); + } + if (d->lag && !lag) + d->lag = d->resume_wc = d->resume_progress = 0; + if (d->resume_wc) { + int64_t elapsed = now - d->resume_wc; + limit = d->resume_progress + (int64_t)(elapsed * d->readrate_catchup); + } else { + limit = max_prog; } + + if (progress > limit) + av_usleep(progress - limit); } static int do_send(Demuxer *d, DemuxStream *ds, AVPacket *pkt, unsigned flags, _______________________________________________ ffmpeg-cvslog mailing list -- [email protected] To unsubscribe send an email to [email protected]
