[FFmpeg-devel] [RFC] ac3dec: use dsputil.clear_block

[Måns Rullgård]

Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:

> Hello,
> this gives an overall speedup of about 1.1 % on Intel Atom with my sample.
> Testing with other CPUs and samples heavily welcome, I suspect a slowdown may 
> be possible, beside it being a bit ugly.
> Index: libavcodec/ac3dec.c
> ===================================================================
> --- libavcodec/ac3dec.c	(revision 21191)
> +++ libavcodec/ac3dec.c	(working copy)
> @@ -565,6 +566,7 @@
>   */
>  static void decode_transform_coeffs(AC3DecodeContext *s, int blk)
>  {
> +    const int clearsize = 64 * sizeof(DCTELEM) / sizeof(s->fixed_coeffs[0][0]);
>      int ch, end;
>      int got_cplchan = 0;
>      mant_groups m;
> @@ -586,9 +588,12 @@
>          } else {
>              end = s->end_freq[ch];
>          }
> -        do
> -            s->fixed_coeffs[ch][end] = 0;
> -        while(++end < 256);
> +        while (end & (clearsize - 1))
> +            s->fixed_coeffs[ch][end++] = 0;
> +        while (end < 256) {
> +            s->dsp.clear_block((DCTELEM *)s->fixed_coeffs[ch] + end);
> +            end += clearsize;
> +        }
>      }

Did you try a simple memset()?

-- 
M?ns Rullg?rd
mans at mansr.com