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

[Andreas Rheinhardt]

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
AVFMT_NOTIMESTAMPS. This is enough to fix the issue with TrueHD and
1/1000 timebases (which also exists for the null muxer).

- Andreas