[FFmpeg-devel] [PATCH] yadif: restore speed of the C filtering code

[Michael Niedermayer]

On Tue, Mar 05, 2013 at 12:57:03AM +0100, James Darnley wrote:
> Always use the special filter for the first and last 3 columns (only).
> 
> The changes made in 64ed397 slowed the filter to just under 3/4 of what
> it was.  This commit restores some of that speed while maintaining
> identical output.
> 
> For reference, on my Athlon64:
> 1733222 decicycles in old
> 2358563 decicycles in new

> 1909653 decicycles in this

why the speedloss relative to the previous patch ?
this is definitly not ok


> ---
>  libavfilter/vf_yadif.c          |   58 +++++++++++++++++----------------------
>  libavfilter/x86/vf_yadif_init.c |   12 ++------
>  libavfilter/yadif.h             |    4 +--
>  3 files changed, 29 insertions(+), 45 deletions(-)
> 
> diff --git a/libavfilter/vf_yadif.c b/libavfilter/vf_yadif.c
> index b7c2d80..7abb3b2 100644
> --- a/libavfilter/vf_yadif.c
> +++ b/libavfilter/vf_yadif.c
> @@ -34,9 +34,9 @@
>  #define PERM_RWP AV_PERM_WRITE | AV_PERM_PRESERVE | AV_PERM_REUSE
>  
>  #define CHECK(j)\
> -    {   int score = FFABS(cur[mrefs + off_left + (j)] - cur[prefs + off_left - (j)])\
> +    {   int score = FFABS(cur[mrefs - 1 + (j)] - cur[prefs - 1 - (j)])\
>                    + FFABS(cur[mrefs  +(j)] - cur[prefs  -(j)])\
> -                  + FFABS(cur[mrefs + off_right + (j)] - cur[prefs + off_right - (j)]);\
> +                  + FFABS(cur[mrefs + 1 + (j)] - cur[prefs + 1 - (j)]);\
>          if (score < spatial_score) {\
>              spatial_score= score;\
>              spatial_pred= (cur[mrefs  +(j)] + cur[prefs  -(j)])>>1;\
> @@ -51,12 +51,10 @@
>          int temporal_diff2 =(FFABS(next[mrefs] - c) + FFABS(next[prefs] - e) )>>1; \
>          int diff = FFMAX3(temporal_diff0 >> 1, temporal_diff1, temporal_diff2); \
>          int spatial_pred = (c+e) >> 1; \
> -        int off_right = (x < w - 1) ? 1 : -1;\
> -        int off_left  = x ? -1 : 1;\
> -        int spatial_score = FFABS(cur[mrefs + off_left]  - cur[prefs + off_left]) + FFABS(c-e) \
> -                          + FFABS(cur[mrefs + off_right] - cur[prefs + off_right]) - 1; \
>   \

>          if (x > 2 && x < w - 3) {\
> +            int spatial_score = FFABS(cur[mrefs - 1] - cur[prefs - 1]) + FFABS(c-e) \
> +                              + FFABS(cur[mrefs + 1] - cur[prefs + 1]) - 1; \
>              CHECK(-1) CHECK(-2) }} }} \
>              CHECK( 1) CHECK( 2) }} }} \
>          }\

you lost a optimization here that was in the previous patch


[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I have never wished to cater to the crowd; for what I know they do not
approve, and what they approve I do not know. -- Epicurus
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