Enhanced coupling support for E-AC-3 / Dolby Digital Plus - with sample file

[BuccoBruce]

Summary of the bug: Enhanced coupling is currently unsupported per eac3dec

  24  * There are several features of E-AC-3 that this decoder does not yet support.
  25  *
  26  * Enhanced Coupling
  27  *     No known samples exist.  If any ever surface, this feature should not be
  28  *     too difficult to implement.

How to reproduce:

% ffplay -i ".\08 - It's Not Unusual_88.ec3"
ffplay version 7.0-full_build-www.gyan.dev Copyright (c) 2003-2024 the FFmpeg developers
  built with gcc 13.2.0 (Rev5, Built by MSYS2 project)
[eac3 @ 000001f4a04c5c80] Enhanced coupling is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[eac3 @ 000001f4a04c5c80] If you want to help, upload a sample of this file to https://streams.videolan.org/upload/ and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)
[eac3 @ 000001f4a04c5c80] error decoding the audio block

It appears that the Dolby encoder previously provided by Rovi (?) for use with Adobe Audition versions prior to 2018 automatically enables enhanced coupling for bitrates lower than 48 kbps per channel. Here's a sample file for you.

Windows 10 is able to decode it using whatever Media Foundation things Groove Music defaults to and outputs PCM. Windows Media Player automatically starts bit-streaming it - I probably have LAV enabled. MPV does too, but if I disable my bit-streaming options in .config, it (understandably) gives the same error that ffmpeg does.

I am not sure where else enhanced coupling exists in the wild as I have never seen DD+ used below 128kbps stereo (64k/ch).

[BuccoBruce]

IT'S NOT UNUSUAL TO BE LOVED BY ANYONE

[BuccoBruce]

at 96 kbps, Enhanced Coupling is no longer active, and the file plays