[FFmpeg-trac] #9471(avformat:open): EAC3 native encoder is only gapless in the beginning, not in the end

[FFmpeg]

#9471: EAC3 native encoder is only gapless in the beginning, not in the end
-------------------------------------+-------------------------------------
             Reporter:  Balling      |                    Owner:  (none)
                 Type:  defect       |                   Status:  open
             Priority:  normal       |                Component:  avformat
              Version:  git-master   |               Resolution:
             Keywords:  eac3         |               Blocked By:
  gapless mp4 editlist               |
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-------------------------------------
Comment (by j7n):

 The padding from E-AC-3 tracks is still not being removed as of May 2025.
 The delay and padding can be variable. The current practice with music
 encoding is to prepend 1 or 2 syncframes shared with the end of the
 previous track to have the decoder prerolled with actual audio data and
 not silence.

 An "elst" box my contain the following data, where 38FE80 is the correct
 end point in samples, and 800 is the delay:

 {{{
 00000000000000010038FE800000080000010000
 }}}

 ffmpeg reports
 {{{
 Chapter #0:0: start 0.042667, end 77.816000
 }}}
 But the decoded file has a duration approximately 77.781 and includes
 extra samples up to the end of the stream.

 Older E-AC-3 files in the wild may contain garbage at the end without an
 elst element. I observe a delay of 256 in Adobe Audition when producing an
 EC3 elementary stream. With old encoders the delay depended on whether the
 90° phase filter was active.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/9471#comment:9>
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