[FFmpeg-devel] [RFC] Re: releases and stuff

[Vitor Sessak]

Michael Niedermayer wrote:
> On Wed, Feb 11, 2009 at 09:48:10PM +0100, Benjamin Larsson wrote:
>> Benjamin Larsson wrote:
>>> Michael Niedermayer wrote:
>>>> On Wed, Feb 11, 2009 at 02:51:43PM +0100, Benjamin Larsson wrote:
>>>>   
>>>>> Michael Niedermayer wrote:
>>>>>     
>>>> [...]
>>>>   
>>>>>>   
>>>>>>       
>>>>>>> Regarding fixed point tables and stuff, the fft routines might behave 
>>>>>>> differently also. To be really sure a complete fixed point version would 
>>>>>>> be needed.
>>>>>>>     
>>>>>>>         
>>>>>> how hard is it to write a fixed point fourier transform? and i mean fourier
>>>>>> not fast fourier
>>>>>>
>>>>>>
>>>>>>   
>>>>>>       
>>>>> The ac3 encoder already have a fixedpoint fft and mdct. We could use 
>>>>> those where needed. Fixed point generation of the mdct tables should be 
>>>>> easy to implement also. Would a solution with a -regtest parameter be 
>>>>>     
>>>> we have -bitexact alraedy and yes fixed point code should then be used
>>>> where possible
>>>>   
>>> Ok, I'll see what I can cook up this evening.
>>>
>>> MvH
>>> Benjamin Larsson
>> The patch is not really fixed point as it uses sinf. But it might be
>> good enough for our needs. If not then some taylor approximation might
>> be appropriate to use.
>>
>> Compiled with --enable-gpl --enable-debug=3 --disable-optimizations
>> --enable-swscale I get this with 4.3.2 on amd64 with these compile options:
>>
>>
>> @@ -205,14 +205,14 @@
>>  353368 ./tests/data/a-flac.flac
>>  95e54b261530a1bcf6de6fe3b21dc5f6 *./tests/data/flac.vsynth.out.wav
>>  stddev:    0.00 PSNR:999.99 bytes:  1058444/  1058444
>> -4435d87463cd6c5407bd88cca241ca56 *./tests/data/a-wmav1.asf
>> +4cd042a85c9c3f52124d6bcdba8cefdb *./tests/data/a-wmav1.asf
>>  106004 ./tests/data/a-wmav1.asf
>> -stddev:12251.38 PSNR: 14.56 bytes:  1056812/  1058444
>> -stddev: 2105.96 PSNR: 29.85 bytes:  1048620/  1058444
>> -24ae726aef89e5d17e315c64182f4c61 *./tests/data/a-wmav2.asf
>> +stddev:12251.32 PSNR: 14.56 bytes:  1056812/  1058444
>> +stddev: 2105.95 PSNR: 29.85 bytes:  1048620/  1058444
>> +36491e6aca4516616e6b0c600330070a *./tests/data/a-wmav2.asf
>>  106044 ./tests/data/a-wmav2.asf
>> -stddev:12255.80 PSNR: 14.55 bytes:  1056812/  1058444
>> -stddev: 2099.27 PSNR: 29.88 bytes:  1048620/  1058444
>> +stddev:12255.59 PSNR: 14.55 bytes:  1056812/  1058444
>> +stddev: 2099.25 PSNR: 29.88 bytes:  1048620/  1058444
>>  89f5b8dd97e0dddbe59af0d44fd229f3 *./tests/data/a-pcm_alaw.wav
>>  529256 ./tests/data/a-pcm_alaw.wav
>>  0568b0b9a72e31559e150e7e09d301cd *./tests/data/pcm.vsynth.out.wav
>> make: *** [codectest] Error 1
>>
>> Would be nice if people could test this with other compilers and other
>> platforms.
> 
> i remember posting some code to do sin/cos with integers using
> bisection of angles and normalization of vectors
> i dont remember the subj/date or what happened with it but
> maybe it could be usefull?

Here: 
http://lists.mplayerhq.hu/pipermail/ffmpeg-devel/2008-November/056314.html

-Vitor