[FFmpeg-user] Audible aax files and concat demuxer

[Hans Carlson]

If I decode an audible aax file using the -activation_bytes option it 
works fine for a single file, eg:

   $ ffmpeg -activation_bytes XXXXXXXX -i part-1.aax -codec copy part-1.mp4

BUT if I try to concat multiple files using the concat demuxer it acts 
like the -activation_bytes option isn't supplied.

This feels like a bug?

   $ cat parts.txt
   file part-1.aax
   file part-2.aax

   $ ffmpeg -activation_bytes XXXXXXXX -f concat -i parts.txt -codec copy parts.mp4
   ffmpeg version N-94778-g787c56b9e9 Copyright (c) 2000-2019 the FFmpeg developers
     built with gcc 7 (GCC)
     configuration: --enable-libfdk-aac
     libavutil      56. 34.100 / 56. 34.100
     libavcodec     58. 56.101 / 58. 56.101
     libavformat    58. 32.104 / 58. 32.104
     libavdevice    58.  9.100 / 58.  9.100
     libavfilter     7. 58.102 /  7. 58.102
     libswscale      5.  6.100 /  5.  6.100
     libswresample   3.  6.100 /  3.  6.100
   [mov,mp4,m4a,3gp,3g2,mj2 @ 0x2c40580] [aax] file checksum == 21cd2a0732a1b2972e61a4e284da6720b2baba9f
   [mov,mp4,m4a,3gp,3g2,mj2 @ 0x2c40580] [aax] activation_bytes option is missing!
   [mov,mp4,m4a,3gp,3g2,mj2 @ 0x2c40580] stream 0, timescale not set
   [aac @ 0x2c41fc0] channel element 2.5 is not allocated
   Option activation_bytes not found.

PS. I can get around this by decoding each part individually and then 
using the concat demuxer on the decoded parts, but the above still seems 
like a bug to me.