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

[Steven Liu]

> 在 2019年10月29日，01:09，Dennis Mungai <dmngaie at gmail.com> 写道：
> 
> 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.

Thanks Dennis, Will push this patch after 24hours if there have no objections.
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Thanks
Steven