[FFmpeg-trac] #9864(avcodec:open): DolbyED2 track cannot be decoded

[FFmpeg]

#9864: DolbyED2 track cannot be decoded
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             Reporter:  Francesco    |                    Owner:  (none)
  Bucciantini                        |
                 Type:  enhancement  |                   Status:  open
             Priority:  wish         |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by Francesco Bucciantini):

 @Balling... about the 44800Hz, it's very simple really. So DolbyE spoofs
 itself as PCM 24bit 48'000Hz stereo when it's carried through SDI, however
 internally its sampling is different. When you encode in DolbyE, you have
 something called frame_loc, also referred to as "Line positioning". This
 value is adjusted according to the frame rate of the file and it dictates
 how many samples are inserted within a certain interval. Dolby set out
 some boundaries that your DolbyE file has to be within and they're
 highlighted here:
 https://developer.dolby.com/globalassets/professional/dolby-e/w08_20466_dolby_e_technical_paper.pdf
 (check page 8)

 Since it's an old document, stuff like UHD 50p is not listed, but I can
 tell you it's line 42.
 Anyway, this means that DolbyE will have its own sampling which isn't
 48'000Hz but rather something lower, internally. In this case, ffmpeg is
 detecting the real internal DolbyE sampling, which is 44'800Hz (very
 unusual, I know, given that people are used to see either 44'100Hz or
 48'000Hz streams, but it's just the way it is). Of course, when for
 instance you play it on a DolbyE compatible hardware decoder, it will
 almost always be brought to 48'000Hz upon decoding by the internal
 circuitry, but since we're living in a software day and age, this will be
 FFMpeg's duty once the stream is decoded, however, the decoder won't do it
 automatically 'cause perhaps you might wanna have the real sampling
 without any resampling so it allows you to get it decoded at the original
 sampling (in this case 44'800Hz given that it's a 25i FULL HD stream on
 line 24).
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9864#comment:24>
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