[M4IF Technotes] Re: mpeg-4 audio reference software

[Ralph Sperschneider]

Marten,
please note, that the encoder does not provide files in mp4 file fomat (although 
they have the suffix .mp4) but in a certain (non-standard) flex-mux format. If 
you want to create an mp4 file, you have to use the appropriate converter 
(fl4_to_mp4), which is part of the reference software. The codec-chain might 
e.g. look as follows:
mp4auenc   -d 1 -m lpc -r 6000 -c -mp4ff m08.au         -o m08_celp6.fl4
fl4_to_mp4 -d 1                          m08_celp6.fl4  -o m08_celp6.mp4
mp4audec   -d 1                          m08_celp6.mp4  -o m08_celp6.au
Please note further, that you have to use the most recent version of the mp4 
file library (libisomedia) in order to successfully decode the conformance test 
sequences (there was a bug in an earlier version of the mp4 file library).
Best regards,
Ralph
PS: My I kindly ask for the version of the referece software you are using?
marten.thielges   student.uni-tuebingen.de wrote:
> Hello,
> 
> I have some trouble with the natural audio reference software, perhaps 
> someone can help:
> 
> I have compiled the software (mp4auenc/mp4audec) for win32 using ms 
> visual c++ 6.0 successfully (including afsp audio file format library 
> and mp4 file format using libisomp4 - not libisomedia).
> 
> I can for example encode an audio file to mpeg-4 celp (the .mp4 file 
> size seems appropriate), but the trouble lies in decoding the resulting 
> .mp4 file.
> mp4audec only returns "WARNING: error decoding audio file .... .mp4".
> I also tried playing the resulting celp files in EnvivioTV (which 
> supports mpeg-4 celp) and it failed as well.
> Trying to decode the official audio conformance celp bitstreams with 
> mp4audec.exe didn't work either :(
> 
> If someone has a working natural audio reference en-/decoder for win, I 
> would be very thankful, if that person could send it to me via email.
> 
> Greets,
> Marten Thielges
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