[Ffmpeg-devel] [RFC] mdct window generation

[Benjamin Larsson]

Hi,

Michael Niedermayer wrote:

>Hi
>
>On Sun, Jul 09, 2006 at 03:31:38PM +0200, Benjamin Larsson wrote:
>  
>
>>My latest patch is quite large so I'll just link it:
>>http://tranquillity.campus.luth.se/~banan/ffmpeg/mdct_window.patch
>>
>>The kbd window generation isn't checked yet as no codec use it but the
>>vorbis and sine window generation works.
>>    
>>
>
>by how much do the generated windows differ from the hardcoded ones?
>please provide max difference & mean squared difference
>  
>
http://tranquillity.campus.luth.se/~banan/ffmpeg/vorbis_window_test.txt
The third column is the difference, fifth is the MSD. The difference
could be caused by diffrent rounding in the initial window calculation.

>why does the window generation code use float instead of double?
>  
>
The difference is neglible IMO.

>and are all windows shared between codec(s) (instances)? 
>
>[...]
>  
>
No, and if they where to be shared all tables had to be generated to
ensure that no table is missing. Regarding vorbis either keep all 32kb
of tables in the binary so they can be shared among instances or only
generate the tables needed at runtime for each instance.



MvH
Benjamin Larsson

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