[FFmpeg-devel] [PATCH 21/24] ffmpeg_mux: split of_write_packet()

[Anton Khirnov]

Quoting Andreas Rheinhardt (2021-12-17 00:42:25)
> Anton Khirnov:
> > diff --git a/fftools/ffmpeg_mux.c b/fftools/ffmpeg_mux.c
> > index d4b674c9e2..e97ec8ab93 100644
> > --- a/fftools/ffmpeg_mux.c
> > +++ b/fftools/ffmpeg_mux.c
> > @@ -102,39 +102,12 @@ static int queue_packet(OutputFile *of, OutputStream *ost, AVPacket *pkt)
> >      return 0;
> >  }
> >  
> > -void of_write_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost,
> > -                     int unqueue)
> > +static void write_packet(OutputFile *of, OutputStream *ost, AVPacket *pkt)
> >  {
> >      AVFormatContext *s = of->ctx;
> >      AVStream *st = ost->st;
> >      int ret;
> >  
> > -    /*
> > -     * Audio encoders may split the packets --  #frames in != #packets out.
> > -     * But there is no reordering, so we can limit the number of output packets
> > -     * by simply dropping them here.
> > -     * Counting encoded video frames needs to be done separately because of
> > -     * reordering, see do_video_out().
> > -     * Do not count the packet when unqueued because it has been counted when queued.
> > -     */
> > -    if (!(st->codecpar->codec_type == AVMEDIA_TYPE_VIDEO && ost->encoding_needed) && !unqueue) {
> > -        if (ost->frame_number >= ost->max_frames) {
> > -            av_packet_unref(pkt);
> > -            return;
> > -        }
> > -        ost->frame_number++;
> > -    }
> 
> Factoring this chunk out of write_packet() (effectively inlining
> unqueue) looks good (and I actually pondered it myself),
> 
> > -
> > -    /* the muxer is not initialized yet, buffer the packet */
> > -    if (!of->mux->header_written) {
> > -        ret = queue_packet(of, ost, pkt);
> > -        if (ret < 0) {
> > -            av_packet_unref(pkt);
> > -            exit_program(1);
> > -        }
> > -        return;
> > -    }
> > -
> 
> but I could not prove that the header has already been written in case
> unqueue == 0. Can you guarantee this to be so and explain it to me?

I don't understand what you mean. unqueue == 0 in the current code tells
you nothing about whether the header has been written.
How does that relate to the patch?

-- 
Anton Khirnov