Modifying headerinformation in aac *.m4a files

[chh]

I have recently bought a Pioneer DCS-575 Home Theater. According to specs., it should be able to play back audio, encoded in MPEG4-AAC, iTunes flavour, and recognize aac audio, if the *.m4a fileextension is used.

I have tried to convert an audio sample from PCM *.wav to AAC *.m4a, with Apple iTunes version 8.2.0.23, and it runs smoothly. Have tried 48KHz source downsampled to 44.1KHz an coded as 256Kbps VBR, an 48KHz coded as 128Kbps CBR. No problems.

Normally I would use MeGui to encode video and audio. In MeGui one can choose from three flavours of AAC, that is Winamp-AAC, FAAC-AAC, or Nero-AAC. Nothing of this wil play in the Pioneer DCS-575

When analyzing the files with Gspot, Nero-AAC seems to come closest to iTunes. See copy/paste below.

My question is then, is there a tool, which can open an *.m4a file, and modify the container- and userdata/metadata information?

Quotes from Gspot, note the small differences:


QuickTime - iTunes:
Container:
M4A : Apple iTunes AAC-LC (.M4A) Audio
- mp42: MP4 v2 [ISO 14496-14]
- isom: MP4 Base Media v1 [IS0 14496-12:2003]
Created: 2009 Jul 13 13:00:36
Modified: 2009 Jul 13 13:00:47

User/Meta data:
©nam:testlyd
©too:iTunes 8.2.0.23, QuickTime 7.6.2


Nero:
Container:
mp42: MP4 v2 [ISO 14496-14]
- M4A : Apple iTunes AAC-LC (.M4A) Audio
- isom: MP4 Base Media v1 [IS0 14496-12:2003]
- ndia: <unknown>
Created: 2009 Jul 13 11:15:12
Modified: 2009 Jul 13 11:15:19

User/Meta data:
©too:Nero AAC codec / 1.3.3.0

[b66pak]

probably is a muxing problem...try this:

demux the neroaac encoded file to raw using mp4box (is in megui>tools>mp4box folder):

mp4box -raw 1 myaudiofile.m4a

you wil get an .aac file

now remux it:

mp4box -add myaacfile.aac -new remuxed.m4a

keep us posted with the result!
_

[chh]

Okay. So I have done as suggested.

Gspot now says:

Container:
M4A : Apple iTunes AAC-LC (.M4A) Audio
- isom: MP4 Base Media v1 [IS0 14496-12:2003]
- mp42: MP4 v2 [ISO 14496-14]
Created: 2009 Jul 13 20:08:43
Modified: 2009 Jul 13 20:08:43

User/Meta data:
( empty - nothing )

Hmm. Looks more like the original iTunes, the container starting with "M4A : Apple iTunes AAC-LC (.M4A) Audio ". What worries me is two missing atoms "©nam:" and "©too".
If the User/Metada "©too:Nero" instead of "©too:iTunes ... " is what the Pioneer trips over, then ...

I will keep you posted, when I have tried to run it on the player. (Won't be able to do so until Friday").

[chh]

A big thanks to b66pak!

The suggested procedure worked like a charm. The Pioneer device plays the converted AAC files.

And even better: I got confirmed, that the Pioneer DCS-575 not only plays conventional 2-channel AAC audio, but also 6-channel AAC audio. Quite usefull when converting movies with large DTS audio-files to MP4.

[b66pak]

thanks for keeping us informed...
_