M4A codec type issue

[keynet]

This ffmpeg flag (moving the MOOV atom to the front of file) prevents faad2 transcoding. Not sure if this applies to all such files or just those made by ffmpeg
FAAD reports "Unable to find correct AAC sound track in the MP4 file."

[keynet]

OK, there's more to it, it's not that.
It appears to be some weirdness with a different AAC codec.
This version works (from mediainfo)
Format : AAC
Format/Info : Advanced Audio Codec
Format profile : HE-AACv2 / HE-AAC / LC
Format settings : Implicit
Codec ID : mp4a-40-2
Duration : 24 min 58 s
Bit rate mode : Variable
Bit rate : 48.0 kb/s
Maximum bit rate : 53.4 kb/s
Channel(s) : 2 channels / 1 channel / 1 channel
Channel positions : Front: L R / Front: C / Front: C
Sampling rate : 44.1 kHz / 44.1 kHz / 22.05 kHz
Frame rate : 21.533 FPS (1024 SPF)

This one doesn't:

ormat : AAC
Format/Info : Advanced Audio Codec
Format profile : HE-AACv2 / HE-AAC / LC
Format settings : NBC
Codec ID : mp4a-40-29
Duration : 26 min 58 s
Duration_LastFrame : -45 ms
Bit rate mode : Constant
Bit rate : 48.0 kb/s
Channel(s) : 2 channels / 1 channel / 1 channel
Channel positions : Front: L R / Front: C / Front: C
Sampling rate : 44.1 kHz / 44.1 kHz / 22.05 kHz
Frame rate : 21.533 FPS (1024 SPF)

[keynet]

Apologies - confirmed, not the MOOV atom, but the "Format settings" string that upsets FAAD2.

I was transcoding some high bitrate AAC recordings to HE-AACv2 podcasts, and it seems ffmpeg was perhaps carrying through the "NBC" tag from the earlier AAC coding.
A workaround is to force the tag to "implicit" per the working version above e.g. using an ffmpeg flag "-signaling implicit". Probably a kludge, but it works for me on about a hundred podcast files.

[ralph-irving]

I'll investigate this in the coming days.

[keynet]

This issue is still there, I just tripped myself up again transcoding some iplayer downloads.
Also the decoding used in Squeezelite can't handle these streams directly, nor it seems even with the above workaround