[FFmpeg-devel] [PATCH] avformat/hls: Set AVFMT_TS_DISCONT flag on HLS input format

[Dennis Mungai]

On Mon, 28 Oct 2019 at 05:45, Steven Liu <lq at chinaffmpeg.org> wrote:
>
>
>
> > 在 2019年10月28日，02:39，Philip Langdale <philipl at overt.org> 写道：
> >
> > There have been many reports over the years about problems when
> > taking an HLS stream as input to `ffmpeg` where there are timestamp
> > discontinuities present. This is explicitly supported in the
> > HLS spec (EXT-X-DISCONTINUITY) and often used for ad injection.
> >
> > Various fixes and work-arounds have been proposed over the years,
> > but one step that seems obvious, even if it's not a complete fix,
> > is to mark the HLS input format as supporting discontinuities. This
> > will prevent timestamp fixup logic in ffmpeg.c kicking in that ends
> > up mangling the timestamps unnecessarily.
> >
> > I've tested this out with an example provided by Joe Koberg early
> > last year, and it is sufficient to allow `ffmpeg` to download and
> > mux the stream correctly. Joe had briefly suggested that other
> > situations can still be handled incorrectly, but this seems like
> > a strict improvement.
> >
> > Joe's example:
> >
> > https://s3.amazonaws.com/playon-test-videos/discont_test_new/discont_test.m3u8
> > ---
> > libavformat/hls.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/libavformat/hls.c b/libavformat/hls.c
> > index d7f4d5b442..ac151d5ca4 100644
> > --- a/libavformat/hls.c
> > +++ b/libavformat/hls.c
> > @@ -2326,7 +2326,7 @@ AVInputFormat ff_hls_demuxer = {
> >     .long_name      = NULL_IF_CONFIG_SMALL("Apple HTTP Live Streaming"),
> >     .priv_class     = &hls_class,
> >     .priv_data_size = sizeof(HLSContext),
> > -    .flags          = AVFMT_NOGENSEARCH,
> > +    .flags          = AVFMT_NOGENSEARCH | AVFMT_TS_DISCONT,
> >     .read_probe     = hls_probe,
> >     .read_header    = hls_read_header,
> >     .read_packet    = hls_read_packet,
> > --
> > 2.20.1
> >
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> >
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>
> LGTM, whatever other more reasons, this can fix one of those problems.
>
> Thanks
> Steven

This patch actually fixes the occurence of DTS and PTS discontinuities
I've been seeing with (some) HLS inputs that have discontinuities due
to ad insertion(s). 10+ hours later without a single discontinuity.