[FFmpeg-devel] [PATCH 1/2] avcodec/ffv1enc: replace 3 double precision log2() by 1 single precision log2()

[Michael Niedermayer <michael@niedermayer.cc>]

This makes the remap finding heuristic much faster

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
---
 libavcodec/ffv1enc.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/libavcodec/ffv1enc.c b/libavcodec/ffv1enc.c
index a09b31218db..2a188ade776 100644
--- a/libavcodec/ffv1enc.c
+++ b/libavcodec/ffv1enc.c
@@ -1390,7 +1390,7 @@ static void encode_float32_remap(FFV1Context *f, FFV1SliceContext *sc,
             int last_mul_index = -1;
             int mul_count = 1 << log2_mul_count;
 
-            score_sum[log2_mul_count] += log2_mul_count;
+            score_sum[log2_mul_count] += log2_mul_count * log2_mul_count;
             for (int i= 0; i<pixel_num; i++) {
                 int64_t val = sc->unit[p][i].val;
                 int mul_index = (val + 1LL)*mul_count >> 32;
@@ -1414,11 +1414,17 @@ static void encode_float32_remap(FFV1Context *f, FFV1SliceContext *sc,
                         }
 
                         cost = FFMAX((delta + mul/2)  / mul, 1);
-                        score_tab[si] += log2(cost);
-                        if (mul > 1)
-                            score_tab[si] += log2(fabs(delta - cost*mul)+1) * (1 + (mul_count > 1));
+                        float score = 1;
+                        if (mul > 1) {
+                            score *= (fabs(delta - cost*mul)+1);
+                            if (mul_count > 1)
+                                score *= score;
+                        }
+                        score *= cost;
+                        score *= score;
                         if (mul_index != last_mul_index)
-                            score_tab[si] += 0.5*log2(mul);
+                            score *= mul;
+                        score_tab[si] += log2f(score);
                     }
                 }
                 last_val = val;
-- 
2.49.0

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