[FFmpeg-devel] [PATCH] lavc/aacenc_utils: unroll quantize_bands loop

[Ganesh Ajjanagadde]

On Sat, Mar 19, 2016 at 4:36 AM, Michael Niedermayer
<michael at niedermayer.cc> wrote:
> On Fri, Mar 18, 2016 at 07:27:46PM -0700, Ganesh Ajjanagadde wrote:
>> Yields speedup in quantize_bands, and non-negligible speedup in aac encoding overall.
>>
>> Sample benchmark (Haswell, -march=native + GCC):
>> new:
>>     [...]
>>     553 decicycles in quantize_bands, 2097136 runs,     16 skips9x
>>     554 decicycles in quantize_bands, 4194266 runs,     38 skips8x
>>     559 decicycles in quantize_bands, 8388534 runs,     74 skips7x
>>
>> old:
>>     [...]
>>     711 decicycles in quantize_bands, 2097140 runs,     12 skips7x
>>     713 decicycles in quantize_bands, 4194277 runs,     27 skips4x
>>     715 decicycles in quantize_bands, 8388538 runs,     70 skips3x
>>
>> old:
>> ffmpeg -f lavfi -i anoisesrc -t 300 -y sin_new.aac  4.58s user 0.01s system 99% cpu 4.590 total
>>
>> new:
>> ffmpeg -f lavfi -i anoisesrc -t 300 -y sin_new.aac  4.54s user 0.02s system 99% cpu 4.566 total
>>
>> Signed-off-by: Ganesh Ajjanagadde <gajjanag at gmail.com>
>> ---
>>  libavcodec/aacenc_utils.h | 33 +++++++++++++++++++++++++--------
>>  1 file changed, 25 insertions(+), 8 deletions(-)
>>
>> diff --git a/libavcodec/aacenc_utils.h b/libavcodec/aacenc_utils.h
>> index 38636e5..0203b6e 100644
>> --- a/libavcodec/aacenc_utils.h
>> +++ b/libavcodec/aacenc_utils.h
>> @@ -62,18 +62,35 @@ static inline int quant(float coef, const float Q, const float rounding)
>>      return sqrtf(a * sqrtf(a)) + rounding;
>>  }
>>
>> +static inline float minf(float x, float y) {
>> +    return x < y ? x : y;
>> +}
>> +
>>  static inline void quantize_bands(int *out, const float *in, const float *scaled,
>>                                    int size, float Q34, int is_signed, int maxval,
>>                                    const float rounding)
>>  {
>> -    int i;
>> -    for (i = 0; i < size; i++) {
> [...]
>> +    for (int i = 0; i < size; i+=4) {
>
> iam not sure we still support a compiler that has a problem with
> that int placement but its not done anywhere else

No problem, changed.

>
> [...]
>
> --
> Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB
>
> In fact, the RIAA has been known to suggest that students drop out
> of college or go to community college in order to be able to afford
> settlements. -- The RIAA
>
> _______________________________________________
> ffmpeg-devel mailing list
> ffmpeg-devel at ffmpeg.org
> http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
>