[Libav-user] Decoding an AAC-LATM 5.1 audio returns errors and only 1 channel with data

Nicolás Dato ndato at 3way.com.ar
Tue Jan 8 22:24:55 CET 2013

Hello there,
I am trying to decode an AAC-LATM file (the one that is attached) that
is being transmitted inside a Transport Stream (Digital Television
The source that is transmitting was sending some months ago a 2
channels audio, and everything was OK.
But then they changed to a 5.1 channels audio, I was using FFMPEG
0.10.5, and the decoding was OK but with some frames (like once per
second)  the decoder couldn't decode and returned error logging
"channel element 0.2 is not allocated", I thought it was a problem
with the frames, and not with the decoder
Then, I tested it by upgrading to FFMPEG 1.0, everything looks the
same as with 0.10.5 untill the error "channel element
0.2.." appears, after this happens the data is different, the
channel 1, 2, 4, 5 and 6 are always in 0 (silence), and the channel 3
has the information (and it looks OK).
Using FFMPEG 1.1 or the git repository code generates the same result
as with FFMPEG 1.0

Is anyone having the same problem?
Any idea? is it a problem with the .aac file or with the decoder?
Can you try decoding the file attached? do you get the same problem?
The file is small but doing something like:
$ ffmpeg -i only_decode_3rd_channel.aac out.wav
$ hexdum -C out.wav | less
you can see that at first it is full of data, but after a while, a lot
of zeros appear (they represents the channels 1, 2, 4, 5 and 6)

Thanks for your help.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: only_decode_3rd_channel.aac
Type: application/octet-stream
Size: 28000 bytes
Desc: not available
URL: <http://ffmpeg.org/pipermail/libav-user/attachments/20130108/d8170b57/attachment.obj>

More information about the Libav-user mailing list