[M4IF Technotes] Re: a question about the ISO reference software.

[Ralph Sperschneider]

Robert Bleidt, Streamcrest Associates wrote:
> Some time ago you responded to the following post on the M4IF reflector:
> 
>     From: "marten.thielges   student.uni-tuebingen.de"
>     <marten.thielges   student.uni-tuebingen.de> 
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>     Subject: [M4IF Technotes] mpeg-4 audio reference software 
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>     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
> 
> 
>     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?
> 
> I have been trying to compile the reference software myself, and it has 
> not been easy. The libtsp.lib code was not easy to get (McGill's ftp 
> server requires you to be on a machine with a fully resolvable static 
> IP, which I consider a little rude), but it was no real problem to 
> understand.
> 
> The MP4 file library is another matter. If I look in the syscore code, I 
> see a libisomp4.dll with a date of 7-6-99. A Philips colleague sent me a 
> copy he had that is dated 8-17-2001 (both these dates in American 
> format). What is the difference between these files and libisomedia? Is 
> there any document or link that explains this?
> 
> At the moment, when I try to run the encoder, it complains:
> 
> mp4auenc: WARNING: BsWriteByte: not enough bits left in buffer
> mp4auenc: WARNING: BsPutBit: error writing bit stream
> 
> The code I have says:
> #define PROGVER "MPEG-4 Natural Audio Encoder (Edition 2001)   20-Aug-2001"
> #define CVSID "$Id: mp4auenc.c,v 1.20 2023/08/15 20:18:53 uhd1 Exp $"
> 
> Do you have any suggestions or insights? >
> ____________________________________________________________
> Robert Bleidt 
> Streamcrest Associates
> +1 408-981-0822 Mobile  +1 408-327-2245 Office
> robert   streamcrest.com   www.streamcrest.com <http://www.streamcrest.com/>
> 

Robert,
the MP4 file library is a component of the Systems part of the MPEG-4 reference 
software. I recommend not to use any precompiled version but to compile the most 
recent sorce code yourself.
Dave Singer can tell you where to get the most recent source code available to 
you, depending on whether or not you are an MPEG member.
Best regards,
Ralph
-- 
Dipl.-Ing. Ralph Sperschneider  | Phone: +49 9131 776 344
FhG IIS-A                       | Fax:   +49 9131 776 398
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