What is an malformed AAC bitstream?

[/df]

I listed the cases where yt-dl applies the fixup above. The uncertainty arises from yt-dl/ffmpeg not knowing how the output will be used, not from the actual "malformation" (a poor description of the situation, probably chosen by a speaker whose first language wasn't English).

Basically (see Wikipedia) streamed AAC (as pulled from HLS fragments) comes with self-synchronising ADTS headers, which an implementation decoding AAC from an MP4 container need not understand. The ffmpeg bitstream filter aac_adtstoasc in the fixup transforms the streamed ADTS-AAC audio into the MPEG-4 Audio Specific Configuration for AAC, which an implementation decoding AAC from an MP4 container is required to understand.

My guess is that the Humax player s/w, which definitely has to be able to play M2TS files with ADTS, also accepts ADTS in MP4.

 

[Black Hole]

That being the case, what we need is yt-dl not to run the fix by default, and then a separate fix process for when the user wishes to export the file...

Or perhaps a tick-box set of "optional extras" in qtube (like I've been asking for).