[FFmpeg-devel] [PATCH] avformat/mux: allow non-monotonic ts with AVFMT_NOTIMESTAMPS

[Anton Khirnov]

Quoting Andreas Rheinhardt (2020-02-26 16:06:00)
> Anssi Hannula:
> > Allow non-monotonic input timestamps for muxers with no timestamps at
> > all (AVFMT_NOTIMESTAMPS).
> > 
> > This is frequently hit when muxing TrueHD with spdifenc as many MKV
> > files use 1ms timestamps while TrueHD frames are shorter than that
> > (1/1200 sec for 48kHz-based and 1/1102.5 sec for 44.1kHz-based rates).
> > ---
> >  libavformat/mux.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/libavformat/mux.c b/libavformat/mux.c
> > index 3533932a58..ba6695badb 100644
> > --- a/libavformat/mux.c
> > +++ b/libavformat/mux.c
> > @@ -622,7 +622,7 @@ static int compute_muxer_pkt_fields(AVFormatContext *s, AVStream *st, AVPacket *
> >      }
> >  
> >      if (st->cur_dts && st->cur_dts != AV_NOPTS_VALUE &&
> > -        ((!(s->oformat->flags & AVFMT_TS_NONSTRICT) &&
> > +        ((!(s->oformat->flags & (AVFMT_NOTIMESTAMPS | AVFMT_TS_NONSTRICT)) &&
> >            st->codecpar->codec_type != AVMEDIA_TYPE_SUBTITLE &&
> >            st->codecpar->codec_type != AVMEDIA_TYPE_DATA &&
> >            st->cur_dts >= pkt->dts) || st->cur_dts > pkt->dts)) {
> > 
> The change looks good, but the description is suboptimal: Your change
> does not blindly allow non-monotonic timestamps. It just drops the
> requirement of strictly monotonic dts for muxers with

You mean 'strictly increasing'. The timestamps should still always be
monotonic - i.e. non-decreasing, but possibly staying the same in
adjacent packets.

Unrelated to the patch - that if() blocks is starting to look utterly
unreadable and should be split.

-- 
Anton Khirnov