[Mp4-tech] AAC versions

[Bernhard Grill]

Jonas Dahlberg wrote:
> Hi all,  this is a question of no importance :-)
> 
> I've just bougth a Nokia phone with mp4 capabilities but can't get it to 
> play AAC audio, neither in a mp4 video or only audio from Quicktime. It 
> seems like AAC audio exporting from quicktime puts the audio in another 
> container compared to the AAC-files allready on the phone, and the 
> phones files can't be played from quicktime but in other players like 
> VLC. The strange thing is that when I use AAC-audio in a MPEG-4 movie 
> it's silence in the phone, so I'm not shure if it is only the container 
> that mess things up. Nokia support had funny but irrelevant answers...
> 

Dear Jonas,
the Nokia Phone is probably complying to the 3GPP Specifications. If so, it 
might refuse the mp4 container file which is slightly different to the 3gpp 
container file format, although both formates are derived from the same ISO base 
file format and very similar. 3gpp insisted on this different flavour. The 
argument was that only in 3gpp-files it can be guaranteed that only the codec 
versions 3gpp mandates or recommends are included. mp4 files in general could 
contain more complex versions of MPEG-4 Video (e.g. Advanced Simple Profile) or 
e.g. AAC Main Profile or the MPEG-4 CELP speech coder which are not included in 
the 3gpp specification. In your case this mechanism might be the cause of 
failure, although the AAC LC tracks created by Quicktime in the mp4 files should 
play on the phone without any problem. Exchanging the mp4 ID in the file with 
the 3G ID is probably already  enough to fix your problem. It is fairly easy 
with the ISO file format reference software to create a tool that fixes this tag 
issue. But there might be an easier way: AFAIK, QT from version 6.5 on can read 
and write the 3GPP file format.
Still, hopefully somebody from Nokia is copying this mail and maybe future 
versions of the phone might be more tolerant to files with the mp4 ID -:).
Best regards,
Bernhard Grill
> Any clues?
> 
> Cheers.
> 
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-- 
Dr. Bernhard Grill                                  email: grl iis.fhg.de
Head of Audio Department, Fraunhofer IIS            phone: +49 9131 776-351
Am Wolfsmantel 33, D-91058 Erlangen, Germany        FAX:   +49 9131 776-398