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

[Benjamin Larsson]

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.

MvH
Benjamin Larsson
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