[FFmpeg-trac] #3921(avcodec:new): Faster RDFT

[FFmpeg]

#3921: Faster RDFT
-------------------------------------+-----------------------------------
             Reporter:  ubitux       |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  fft rdft     |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
-------------------------------------+-----------------------------------

Comment (by ubitux):

 The blog post references https://github.com/alexkay/fft-bench which works
 with a few adjustments.

 The benchmark was using an i7 920 (no AVX). On an AVX capable CPU
 (i7-3520M) I obtained this:

 {{{
 lavc/i  9       56
 fftw/i  9       53
 fftw/o  9       51
 djbf/i  9       88
 lavc/i  10      59
 fftw/i  10      52
 fftw/o  10      52
 djbf/i  10      98
 lavc/i  11      60
 fftw/i  11      50
 fftw/o  11      53
 djbf/i  11      106
 lavc/i  12      66
 fftw/i  12      71
 fftw/o  12      56
 djbf/i  12      115
 lavc/i  13      81
 fftw/i  13      71
 fftw/o  13      65
 djbf/i  13      126
 }}}

 I started having a look but no ASM is yet written, only the C boilerplate
 to enable the potential optimized code.

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Ticket URL: <https://trac.ffmpeg.org/ticket/3921#comment:4>
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