[FFmpeg-devel] [PATCH/RFC] Add some dsputil functions useful for AAC decoder

[Michael Niedermayer]

On Sun, Sep 20, 2009 at 03:02:37PM +0100, M?ns Rullg?rd wrote:
[...]
> samples  %        symbol name
> 1274     31.8261  decode_ics
> 676      16.8873  butterflies_float_c                   !!!
> 493      12.3158  vector_fmul_scalar_vp_2_c             !!!
> 203       5.0712  fft_pass_neon
> 176       4.3967  ff_imdct_half_neon
> 169       4.2218  ff_vector_fmul_window_neon
> 150       3.7472  aac_decode_frame
> 138       3.4474  vector_fmul_scalar_c                  !!!
> 106       2.6480  vector_fmul_scalar_vp_4_c             !!!
> 85        2.1234  fft16_neon
> 76        1.8986  ff_float_to_int16_interleave_neon
> 64        1.5988  vp_fmul_scalar_2_c                    !!!
> 41        1.0242  imdct_and_windowing
> 35        0.8743  output_packet
> 30        0.7494  fft8_neon
> 22        0.5496  av_rescale_rnd
> 22        0.5496  vp_fmul_scalar_4_c                    !!!
> 
> And here for another one:
> 
> samples  %        symbol name
> 940      24.7173  butterflies_float_c                   !!!
> 847      22.2719  decode_ics
> 344       9.0455  vector_fmul_scalar_vp_4_c             !!!
> 288       7.5730  fft_pass_neon
> 221       5.8112  ff_imdct_half_neon
> 201       5.2853  ff_vector_fmul_window_neon
> 99        2.6032  vector_fmul_scalar_vp_2_c             !!!
> 98        2.5769  ff_float_to_int16_interleave_neon
> 98        2.5769  fft16_neon
> 91        2.3928  aac_decode_frame
> 89        2.3403  vp_fmul_scalar_4_c                    !!!
> 60        1.5777  vp_fmul_scalar_2_c                    !!!
> 46        1.2096  fft8_neon
> 40        1.0518  av_encode
> 36        0.9466  imdct_and_windowing
> 30        0.7889  output_packet
> 19        0.4996  __divdi3
> 17        0.4470  __udivsi3
> 16        0.4207  vector_fmul_scalar_c                  !!!
> 
> As you can see, the relative time spent in these functions varies a
> lot depending on the sample.
> 

> It is my opinion that everything which can be optimised should be
> optimised.

i doubt that taken litterally, this is your oppinion ... optimizing
in MMX/SSE/NEON some init code run once per invocation of ffmpeg and
that takes only 1ms on a slow embeded system as is ...

about this specific case here, we dont disagree, all the functions seem
to be run often enough to warrant optimizing them

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
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