[FFmpeg-devel] [PATCH] lavf/utils: reset event_flags if extradata is not extracted correctly

[Linjie Fu]

On Mon, Jan 25, 2021 at 9:08 PM Anton Khirnov <anton at khirnov.net> wrote:
>
> Quoting Linjie Fu (2021-01-25 04:49:21)
> > On Mon, Jan 25, 2021 at 12:49 AM Anton Khirnov <anton at khirnov.net> wrote:
> > >
> > > Quoting Linjie Fu (2021-01-24 16:05:56)
> > > > Regression since 87f0c8280.
> > > >
> > > > If the extradata of a stream could not be extracted correctly,
> > > > codec_info_nb_frames would remain zero, while st->event_flag would still
> > > > be marked as AVSTREAM_EVENT_FLAG_NEW_PACKETS.
> > > >
> > > > The two expressions could be different in this case, hence reset
> > > > event_flags and calculate the correct score.
> > > >
> > > > Fix #9029.
> > >
> > > The ticket mentions ffplay, but ffplay does not access event_flags.
> > >
> >
> > You are right, this helps ffmpeg cmdline to copy and dump:
> > $ ffmpeg -i sample_cut.flv -c copy -y dump.mp4
> >
> > Before 87f0c8280 and after this patch:
> >
> > audio streams could be dumped and playable, while video streams still not.
> >
> > 87f0c8280..master:
> > Error reporting and quits.
> >
> > [mp4 @ 0x7fb276809a00] dimensions not set
> > Could not write header for output file #0 (incorrect codec parameters
> > ?): Invalid argument
> > Error initializing output stream 0:1 --
> >
> > I'd change the commit message to "#9029 related" for this, since the
> > ffplay issue remains the same.
>
> I am still not convinced this is really a regression. You can still
> process the file by explicitly mapping only the audio stream.
Okay, I'm fine with this if it won't trigger failures for to different paths.

> This file is damaged and the video stream is not readable. IMO it is
> better to report an error and let the user decide what to do with it
> than silently skip the video stream while pretending everything is fine.
VLC is able to decode/play this correctly, hence maybe need to
investigate more into this.

- linjie