[FFmpeg-devel] [PATCH] Move Kaiser-Bessel Derived window to mdct.c

[Benjamin Larsson]

Robert Swain wrote:
> Hello,
> 
> The SoC AAC code uses a slightly more flexible version (variable
> alpha, window size, iterations) of the Kaiser-Bessel Derived window
> used in libavcodec/ac3dec.c. It is desirable to have the code shared
> between ac3dec.c and aac.c rather than duplicated. I extended the
> capability of the code in ac3dec.c and moved it to mdct.c. Please find
> a patch for this attached.
> 
> It seems that gcc -O3 optimises away local_window[] (I stumbled upon
> this while debugging) and I wasn't sure whether to retain the use of
> doubles for the calculations or to remove local_window[], use window[]
> for temporary storage and change types of variables from double to
> float. Any advice on what to consider for this would be appreciated.
> 
> Best regards,
> Rob
> 

Don't worry, you only need floats.  If you look in the specs you'll see
that the generated coeffs with float will match with the table.

MvH
Benjamin Larsson