ref: 20b855c33e41363a680d463ac6dba7fe07ffe712
parent: 4b6219cb33392fb68f60ec4717a0228c4a453bdc
author: Johann <johannkoenig@google.com>
date: Wed Dec 22 06:15:56 EST 2010
improve integer version of filter the lookup table is based on floating point calculations (see source) by moving the *3 before the downshift and adding the rounding bit, the delta (LUT - integer) goes from: ______________________________________ __ 1__ 1______________________________ __ 1__ 1______________________________ ____ 1______ 1________________________ ____ 1 2__ 2 1________________________ ______ 1 1 2__ 2__ 2__ 2 1 1__________ ________ 1 1 2 2__ 1 2 3 1 2__ 2__ 2__ to: __-1__-1______________________________ ______________________________________ ____-1______-1________________________ ______________________________________ ________-1______________-1____________ ______________________________________ it's important to be able to use the integer version because the LUT more or less precludes SIMD optimizations Change-Id: I45a81127dc7b72a06fba951649135d9d918386c0
--- a/vp8/encoder/temporal_filter.c
+++ b/vp8/encoder/temporal_filter.c
@@ -36,27 +36,34 @@
#define ALT_REF_MC_ENABLED 1 // dis/enable MC in AltRef filtering
#define ALT_REF_SUBPEL_ENABLED 1 // dis/enable subpel in MC AltRef filtering
+#define USE_FILTER_LUT 0 // use lookup table to improve filter
-#define USE_FILTER_LUT 1
#if VP8_TEMPORAL_ALT_REF
#if USE_FILTER_LUT
+// for (strength = 0; strength <= 6; strength++) {
+// for (delta = 0; delta <= 18; delta++) {
+// float coeff = (3.0 * delta * delta) / pow(2, strength);
+// printf("%3d", (int)roundf(coeff > 16 ? 0 : 16-coeff));
+// }
+// printf("\n");
+// }
static int modifier_lut[7][19] =
{
// Strength=0
- {16, 13, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+ {16, 13, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
// Strength=1
- {16, 15, 10, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+ {16, 15, 10, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
// Strength=2
- {16, 15, 13, 9, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+ {16, 15, 13, 9, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
// Strength=3
- {16, 16, 15, 13, 10, 7, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+ {16, 16, 15, 13, 10, 7, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
// Strength=4
- {16, 16, 15, 14, 13, 11, 9, 7, 4, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0},
+ {16, 16, 15, 14, 13, 11, 9, 7, 4, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0},
// Strength=5
- {16, 16, 16, 15, 15, 14, 13, 11, 10, 8, 7, 5, 3, 0, 0, 0, 0, 0, 0},
+ {16, 16, 16, 15, 15, 14, 13, 11, 10, 8, 7, 5, 3, 0, 0, 0, 0, 0, 0},
// Strength=6
- {16, 16, 16, 16, 15, 15, 14, 14, 13, 12, 11, 10, 9, 8, 7, 5, 4, 2, 1}
+ {16, 16, 16, 16, 15, 15, 14, 14, 13, 12, 11, 10, 9, 8, 7, 5, 4, 2, 1}
};
#endif
static void vp8_temporal_filter_predictors_mb_c
@@ -140,16 +147,14 @@
int pixel_value = *frame2++;
#if USE_FILTER_LUT
- // LUT implementation --
- // improves precision of filter
modifier = abs(src_byte-pixel_value);
modifier = modifier>18 ? 0 : lut[modifier];
#else
- modifier = src_byte;
- modifier -= pixel_value;
+ modifier = src_byte - pixel_value;
modifier *= modifier;
- modifier >>= strength;
modifier *= 3;
+ modifier += 1 << (strength - 1);
+ modifier >>= strength;
if (modifier > 16)
modifier = 16;