[FFmpeg-devel] [PATCH] QCELP decoder

Kenan Gillet kenan.gillet
Sun Oct 12 02:32:26 CEST 2008

On Oct 11, 2008, at 9:26 AM, Michael Niedermayer wrote:

> On Sat, Oct 11, 2008 at 12:30:48PM +0200, Benjamin Larsson wrote:
>> Hi.
>>> The patch using the reference code is at [2].
>>> As a plan of action, I propose to work on the inclusion of this  
>>> patch
>>> as a first
>>> step, and then continue on working the SoC decoder
>>> what do you think ?
>> Well we removed the amr reference code support because of license
>> issues, so I don't think we should add more code in. The best way  
>> to do
>> this is to add working reference glue code to the SoC qcelp tree.
> i agree

ok, i have starting to get familiar with the code.

>> Then
>> port the current decoder to fixed point. Then make sure the decoder  
>> is
>> bit exact compared to the reference source. This would remove any  
>> doubt
>> of compliance but it would be alot of work. There is lots of fixed  
>> point
>> code available in in the g729 patches that are aimed for speech  
>> codecs.
>> So are you up for all that work ? You could get svn commit access  
>> to the
>> qcelp soc tree if that would help out your work and the review  
>> process.
> i think we should be aiming at a float+fixed point implementation
> both have advantages. I do not think throwing the float away and  
> replacing
> it by fixed point is such a good idea. fixed point likely is slower on
> modern cpus but then its very usefull for regression tests and fpu- 
> less
> cpus.
> Also bit exactness and sharing code between g729, amr and qcelp may  
> become
> tricky though of course both should be attepted where its possible,  
> where its
> not some compromise has to be found.

It sounds much bigger of a project that I envision. But I am really  
interested in
getting it down the right way.

My only concern would be about the fixed point reference code, because  
code at [1] looks like a float implementation to me, and that the only  
code I am aware of.
I have been googling to get some fixed point reference but could not  
find any
so far.


[1] http://www.3gpp2.org/Public_html/specs/Software_Distribution_vA-1.0_for_C.S0020-Av1.0_13k_Specification.zip

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