02-17-2009 05:59 PM
We are trying to decode AMR from a (any) 3gp file using MP4 Demuxer. The problem is that the decoder delivers audio that sounds like gurgling/alien speak.
Are there any special transformations needed for this to work?
02-18-2009 03:36 AM
No special requirements. Maybe the problem is in MP4 multiplexor? What decoder do you use? Anyway if you attach your 3gp file I can have a look at it. If it is played OK on some player it should be also played by simple_player (IPP sample).
02-19-2009 05:59 AM
Thanks for replying.
We have tried multiple .3gp files, that contain AMR. Unfortunately non of them worked. We are not multiplexing them ourselves.
We are usingUSC_GSMAMR_Fxns to decode these audio frames.
In VLC it says "samr" and simple_player says that the format is not supported, but the MP4 Splitter returns AMR.
One if the files we used we got fromhttp://freemobilvideos.com/getfile.php?ID=608
04-23-2009 03:21 PM
I just migrated to IPP 6.0 from an older version and now I seem to have the same problem as you (strange voice). It used to work well on IPP 4.1. Did you have any success with decoding GSMAMR? If so I would be greatful if you pointed me to the solution.
05-12-2009 07:59 AM
I have isolated a bit more the problem. When I us the IPP 6.0 library and force it to use:
ippStaticInitCpu(ippCpuPP), I get good audio. My detected CPU is ippCpuEM64T (I have a Pentium D dual core processor) and I work under Windows XP 32bit. I have tried to isolate the function responsible for this by prefixing all the calls with px_ to force the call of the C optimized library, but that did notfix the problem. It seems that the problem comes from a hidenlow level function.
New Contributor II
05-14-2009 04:05 AM
IPP team appreciates your effort in investigating the issue. It would be helpful you to try to start with working PX code (ippCpuPP) by perfixing IPP funcions with t7_ dispatching it to the code appropriate to ippCpuEM64T. Starting with the working code you willdefinitely identify the suspicious function.
Vyacheslav, IPP, speech coding domain
05-15-2009 04:16 PM
We rewrote the bitstream unpacker for the storage format and pass that directly to the decoder. Everything works fine now. Take a look at the 26073-800 reference impl at 3gpp.
New Contributor II
05-19-2009 03:54 AM
06-11-2009 06:21 AM
I have been on a differentproject and just read your suggestion. It is a good idea. I'll try it as soon as I have the opportunity. I will also report my findings to the premium support channel as you suggest in a latter message (I am already a registered user).