[FFmpeg-devel] [PATCH] Fix segment muxer

[Vasily]

I used that value somewhere during patch development, but I eventually
settled on -1, because that "start_pts" and "end_pts" are using some other
units, not the unit used by pkt->pts.

So I wanted to make a distinction. Though a possibility of negative
timestamps didn't come to me, so I probably have to change it back to
AV_NOPTS_VALUE.

P.S. Thanks for reviewing my patch!


вс, 6 окт. 2019 г., 13:56 Marton Balint <cus at passwd.hu>:

>
>
> On Thu, 3 Oct 2019, just.one.man at yandex.ru wrote:
>
> > It seems that my first attempt to send the patch failed (probably
> because my box where I executed "git send-email" failed reverse smtp
> check), so I'm going to re-send it to this same thread.
> >
> > ---
> >
> > When incoming media has non-zero start PTS,
> > segment muxer would fail to correctly calculate
> > the point where to chunk segments, as it always
> > assumed that media starts with PTS==0.
> >
> > This change removes this assumption by remembering
> > the PTS of the very first frame passed through the muxer.
> >
> > Also fix starting points of first segment
> > ---
> > libavformat/segment.c |   12 +++++++++++-
> > 1 file changed, 11 insertions(+), 1 deletion(-)
> >
> > diff --git a/libavformat/segment.c b/libavformat/segment.c
> > index e308206..2478d8f 100644
> > --- a/libavformat/segment.c
> > +++ b/libavformat/segment.c
> > @@ -87,6 +87,7 @@ typedef struct SegmentContext {
> >     int64_t last_val;      ///< remember last time for wrap around
> detection
> >     int cut_pending;
> >     int header_written;    ///< whether we've already called
> avformat_write_header
> > +    int64_t start_pts;     ///< pts of the very first packet processed,
> used to compute correct segment length
> >
> >     char *entry_prefix;    ///< prefix to add to list entry filenames
> >     int list_type;         ///< set the list type
> > @@ -702,6 +703,7 @@ static int seg_init(AVFormatContext *s)
> >         if ((ret = parse_frames(s, &seg->frames, &seg->nb_frames,
> seg->frames_str)) < 0)
> >             return ret;
> >     } else {
> > +        seg->start_pts = -1;
>
> AV_NOPTS_VALUE would be probably better for this purpose, even if the
> muxer won't get negative timestamps unless allowed by the
> AVFMT_TS_NEGATIVE flag.
>
> Regards,
> Marton
>
> >         /* set default value if not specified */
> >         if (!seg->time_str)
> >             seg->time_str = av_strdup("2");
> > @@ -914,7 +916,15 @@ calc_times:
> >                 seg->cut_pending = 1;
> >             seg->last_val = wrapped_val;
> >         } else {
> > -            end_pts = seg->time * (seg->segment_count + 1);
> > +            if (seg->start_pts != -1) {
> > +                end_pts = seg->start_pts + seg->time *
> (seg->segment_count + 1);
> > +            } else if (pkt->stream_index == seg->reference_stream_index
> && pkt->pts != AV_NOPTS_VALUE) {
> > +                // this is the first packet of the reference stream we
> see, initialize start point
> > +                seg->start_pts = av_rescale_q(pkt->pts, st->time_base,
> AV_TIME_BASE_Q);
> > +                seg->cur_entry.start_time = (double)pkt->pts *
> av_q2d(st->time_base);
> > +                seg->cur_entry.start_pts = seg->start_pts;
> > +                end_pts = seg->start_pts + seg->time *
> (seg->segment_count + 1);
> > +            }
> >         }
> >     }
> >
> > --
> > 1.7.9.5
> > _______________________________________________
> > ffmpeg-devel mailing list
> > ffmpeg-devel at ffmpeg.org
> > https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
> >
> > To unsubscribe, visit link above, or email
> > ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> https://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>
> To unsubscribe, visit link above, or email
> ffmpeg-devel-request at ffmpeg.org with subject "unsubscribe".