On Thu, Mar 26, 2020 at 10:47:37AM +0100, Anton Khirnov wrote:
> Quoting Andreas Rheinhardt (2020-03-20 17:51:41)
> > Jan Ekström:
> > > On Fri, Mar 20, 2020 at 5:45 PM <lance.lmw...@gmail.com> wrote:
> > >>
> > >> From: Limin Wang <lance.lmw...@gmail.com>
> > >>
> > >> This fixes webvtt segment output.
> > >>
> > >> Please testing with the following command and check the output:
> > >> ./ffmpeg -i ../fate-suite/sub/MicroDVD_capability_tester.srt -f segment
> > >> -segment_time 10 \
> > >> -segment_list_size 0 -segment_list sub.m3u8 -segment_format webvtt
> > >> -scodec webvtt sub-%d.vtt
> > >>
> > >>
> > >> Signed-off-by: Limin Wang <lance.lmw...@gmail.com>
> > >> ---
> > >> fftools/ffmpeg.c | 1 +
> > >> tests/ref/fate/binsub-movtextenc | 2 +-
> > >> tests/ref/fate/sub2video | 86 ++++++++++++++++----------------
> > >> 3 files changed, 45 insertions(+), 44 deletions(-)
> > >>
> > >> diff --git a/fftools/ffmpeg.c b/fftools/ffmpeg.c
> > >> index aaaf241314..c5a2d0731d 100644
> > >> --- a/fftools/ffmpeg.c
> > >> +++ b/fftools/ffmpeg.c
> > >> @@ -1054,6 +1054,7 @@ static void do_subtitle_out(OutputFile *of,
> > >> else
> > >> pkt.pts += av_rescale_q(sub->end_display_time,
> > >> (AVRational){ 1, 1000 }, ost->mux_timebase);
> > >> }
> > >> + pkt.flags |= AV_PKT_FLAG_KEY;
> > >> pkt.dts = pkt.pts;
> > >> output_packet(of, &pkt, ost, 0);
> > >> }
> > >
> > > I do wonder if this is just a case of people forgetting to set the
> > > flag for the relevant packets in the relevant modules?
> > >
> > > I'm not sure if all API users should be forced to handle this
> > > separately. If the packets are decode'able by themselves, they should
> > > be marked as such.
> > >
> > > (Unfortunately, this probably means that all subtitle encoders and
> > > text-based subtitle format demuxers would have to be updated where
> > > this flag is not set)
> > >
> > av_read_frame() already sets the AV_PKT_FLAG_KEY-flag for all subtitle
> > packets (see is_intra_only() in libavformat/utils.c; the subtitle
> > demuxer based around FFDemuxSubtitlesQueues actually have the flag set
> > even before it reaches is_intra_only()). One could do something similar
> > in libavformat/mux.c.
> > But are we actually sure that all subtitle packets are decodable by
> > themselves? IIRC this is not true for all PGS subtitles.
> >
> > - Andreas
> >
> > PS: The semantics of the AV_CODEC_PROP_INTRA_ONLY-flag seem to be based
> > around the assumption that subtitle packets are always intra-only: It is
> > only for video and audio-codecs only.
>
> I would interpret it as simply not being defined for subtitles, rather
> than saying they are all always intra only. So we can always add new
> semantics for subtitles to it.+1 [...] -- Michael GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB The real ebay dictionary, page 2 "100% positive feedback" - "All either got their money back or didnt complain" "Best seller ever, very honest" - "Seller refunded buyer after failed scam"
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