[FFmpeg-devel] [PATCH] Replace CLAMP_TO_SHORT with av_clip in adpcm.c

[Aurelien Jacobs]

On Sat, 11 Aug 2007 12:02:38 +0200
Michael Niedermayer <michaelni at gmx.at> wrote:

> Hi
> 
> On Sat, Aug 11, 2007 at 02:13:51AM -0300, Ramiro Ribeiro Polla wrote:
> > Aurelien Jacobs wrote:
> > > Hi,
> > >
> > > $subj
> > > This fixes issue84.
> > >
> > >   
> > 
> > What about making av_clip_int16 in libavutil/common.h?
> > There are many more places throughout FFmpeg where this is used.

Attached is an implementation of av_clip_int16().

> what is the speed/filesize effect of such a change?

I benchmarked the 3 versions (original CLAMP_TO_SHORT, initial patch
using av_clip, new patch using av_clip_int16).

> speed being:
> volatile int v=0;
> START_TIMER
> for(i=-40000; i<40000; i++)
>     v+= av_clip_int16(i)
> STOP_TIMER("foober")
> printf("%d", v);

Here are the result of this speed benchmark:

6184290 dezicycles in CLAMP_TO_SHORT, 1 runs, 0 skips
6184370 dezicycles in av_clip, 1 runs, 0 skips
5235530 dezicycles in av_clip_int16, 1 runs, 0 skips

av_clip_int16 is a clear winner here.

> filesize being object size with --enable-small

Object size of adpcm.o and ffmpeg with --enable-small:
   text	   data	    bss	    dec	    hex	filename
  14382	   2164	      0	  16546	   40a2	libavcodec/adpcm.o.orig
2493191	  45804	1017840	3556835	 3645e3	ffmpeg.orig
  14377	   2164	      0	  16541	   409d	libavcodec/adpcm.o.av_clip
2493175	  45804	1017840	3556819	 3645d3	ffmpeg.av_clip
  14209	   2164	      0	  16373	   3ff5	libavcodec/adpcm.o.av_clip_int16
2492967	  45804	1017840	3556611	 364503	ffmpeg.av_clip_int16

Once again, av_clip_int16 is a clear winner.

So I will commit soon this av_clip_int16 implementation.

Aurel
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