VP8: faster filter_level clip

(cherry picked from commit a1b227bb533f173354795124e0b966277c251b56)

diff --git a/libavcodec/vp8.c b/libavcodec/vp8.c
index bcf6237..1db57e4 100644 (file)
--- a/libavcodec/vp8.c
+++ b/libavcodec/vp8.c
@@ -1480,7 +1480,10 @@ static av_always_inline void filter_level_for_mb(VP8Context *s, VP8Macroblock *m
         filter_level += s->lf_delta.ref[mb->ref_frame];
         filter_level += s->lf_delta.mode[mb->mode];
     }
-    filter_level = av_clip(filter_level, 0, 63);
+
+/* Like av_clip for inputs 0 and max, where max is equal to (2^n-1) */
+#define POW2CLIP(x,max) (((x) & ~max) ? (-(x))>>31 & max : (x));
+    filter_level = POW2CLIP(filter_level, 63);
 
     interior_limit = filter_level;
     if (s->filter.sharpness) {