[FFmpeg-trac] #6915(avformat:new): DASH audio segments duration doesn't match exactly with video segments duration.

[FFmpeg]

#6915: DASH audio segments duration doesn't match exactly with video segments
duration.
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             Reporter:  beloko      |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avformat
              Version:  git-master  |               Resolution:
             Keywords:              |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
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Comment (by j_karthic):

 Replying to [comment:14 stevenliu]:
 > Replying to [comment:13 j_karthic]:
 > > Replying to [comment:12 stevenliu]:
 > > > Replying to [comment:11 j_karthic]:
 > > > > Replying to [comment:10 stevenliu]:
 > > > > > Replying to [comment:9 j_karthic]:
 > > > > > > Replying to [comment:8 stevenliu]:
 > > > > > > > Replying to [comment:7 j_karthic]:
 > > > > > > > > Well, if we round the target duration to '''nearest
 integer''' as per the spec, part of the problem is resolved. Right now we
 are '''ceiling to the upper integer''' which is not according to HLS
 specifications.
 > > > > > > > >
 > > > > > > > > {{{
 > > > > > > > > 4.3.3.1.  EXT-X-TARGETDURATION
 > > > > > > > >
 > > > > > > > >    The EXT-X-TARGETDURATION tag specifies the maximum
 Media Segment
 > > > > > > > >    duration.  The EXTINF duration of each Media Segment in
 the Playlist
 > > > > > > > >    file, when rounded to the nearest integer, MUST be less
 than or equal
 > > > > > > > >    to the target duration; longer segments can trigger
 playback stalls
 > > > > > > > >    or other errors.  It applies to the entire Playlist
 file.  Its format
 > > > > > > > >    is:
 > > > > > > > >
 > > > > > > > >    #EXT-X-TARGETDURATION:<s>
 > > > > > > > >
 > > > > > > > >    where s is a decimal-integer indicating the target
 duration in
 > > > > > > > >    seconds.  The EXT-X-TARGETDURATION tag is REQUIRED.
 > > > > > > > >
 > > > > > > > > }}}
 > > > > > > > >
 > > > > > > > > So as per the spec, the EXT-X-TARGETDURATION should
 rounded to 4 instead of 5.
 > > > > > > > >
 > > > > > > > > But when I submitted a patch for fixing such an issue in
 hlsenc, it was rejected by Steven. See thread http://ffmpeg.org/pipermail
 /ffmpeg-devel/2017-September/215630.html more details. During that time, I
 was not able to provide a concrete example with mediastreamvalidator like
 @beloko has done now. But I thought the spec was very clear about it
 without any room for confusion.
 > > > > > > > >
 > > > > > > > > @stevenliu
 > > > > > > > > If you have a change of mind after seeing these results,
 please let me know. Maybe I will send a new patch which fixes the target
 duration in dashenc, and we can take forward our discussions there.
 > > > > > > >
 > > > > > > > The spec said "EXT-X-TARGETDURATION must > EXTINF", we have
 talk and you have sent twice patch about it. you can see the spec said
 "MUST be less than or equal to the target duration.", attention the MUST,
 MUST, MUST, we should don't care the tool, we should care the spec. If the
 tool different with the spec, that maybe apple's mistake, you should push
 apple.
 > > > > > > I think you missing the important line "'''when rounded to the
 nearest integer'''" in the spec. I am also only talking about the spec.
 This is just a pure argument, about interpreting that English line. This
 is where I feel some other people in the ffmpeg community should also
 pitch in moderate a discussion, rather than leaving it as "'''Maintainer
 is always right'''".
 > > > > > '''Maintainer''' not always right, but can you give me the mean
 '''MUST be less than or equal  to the target duration''' how should i
 understand it?
 > > > > "'''when rounded to the nearest integer, MUST be less than or
 equal to the target duration'''" is in one sentence. That should be read
 in conjunction with the phrase "when rounded to the nearest integer". It
 means after rounding duration to the nearest integer, it MUST be less than
 or equal to the target duration.
 > > > how should i understand the '''target duration'''?
 > > > do you mean, when the '''EXTINF''' is '''1.080000''', the
 '''EXT-X-TARGETDURATION''' should equal to '''1''' ?
 > > As per the spec, Yes.
 > I coding for hls from VERSION 1, from old VERSION,
 https://tools.ietf.org/html/draft-pantos-http-live-streaming-03
 > about the EXT-X-TARGETDURATION said:
 >
 >
 > {{{
 > 3.2.1.  EXT-X-TARGETDURATION
 >
 >    The EXT-X-TARGETDURATION tag specifies the maximum media file
 >    duration.  The EXTINF duration of each media file in the Playlist
 >    file MUST be less than or equal to the target duration.  This tag
 >    MUST appear once in the Playlist file.  Its format is:
 >
 >    #EXT-X-TARGETDURATION:<s>
 >
 >    where s is an integer indicating the target duration in seconds.
 > }}}
 >
 > so, i always understand it to EXT-X-TARGETDURATION must large than
 EXTINF,
 > I have sent a Email to hls team of apple for check this description,
 maybe there have some misunderstanding words here.
 In that version of HLS, floating point segment duration was not supported.
 The segment durations were already integers. Hence there is no question of
 rounding, when target duration was being defined.
 But later when the floating point segment duration was supported in HLS,
 the definition for target duration was modified to specify "when rounded
 to nearest integer" to handle floating point segment durations.
 >
 >
 > > >
 > > > > > > >
 > > > > > > > >
 > > > > > > > >
 > > > > > > > >
 > > > > > > > >
 > > > > > > > >

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Ticket URL: <https://trac.ffmpeg.org/ticket/6915#comment:15>
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