[FFmpeg-devel] [PATCH] Port AAC decoder to use ff_imdct_half and vector_fmul_window

[Guillaume POIRIER]

Hello,

On Fri, Aug 22, 2008 at 4:22 PM, Guillaume POIRIER <poirierg at gmail.com> wrote:
> Hello,
>
> On Fri, Aug 22, 2008 at 4:18 PM, Robert Swain <robert.swain at gmail.com> wrote:
>> 2008/8/22 Robert Swain <robert.swain at gmail.com>:
>
> [..]
>
>> Just for fun, for the same file, I benchmarked FAAD. Taking the best
>> user time and comparing to the ffaac decoder with the posted patches,
>> I infer that ffaac is ~135% faster than FAAD. :) Benchmark results

[..]

> I'm not surprised. The FFT used in FAAC is very inefficient and slow.

Woops, we're talking about decoding here, hence faaD! Sorry for the noise!
(what I said about FAAC still stands though, see an Oprofile output:
CPU: Core 2, speed 1868.16 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a
unit mask of 0x00 (Unhalted core cycles) count 100000
samples  %        symbol name
39080    21.9734  fft_proc
35505    19.9633  QuantizeBand
26102    14.6763  FixNoise
24012    13.5012  AACQuantize
10854     6.1029  PutBit
5232      2.9418  reorder
4510      2.5358  PsyBufferUpdate
4472      2.5145  MDCT
3537      1.9887  MSEncode
2914      1.6385  PsyCheckShort
2613      1.4692  CalcAllowedDist
2558      1.4383  FilterBank
2382      1.3393  CalcAvgEnrg
2215      1.2454  BalanceEnergy
2086      1.1729  CalcBits
1926      1.0829  faacEncEncode
1899      1.0677  OutputBits)

Guillaume
-- 
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 -- Pierre Desproges