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smartYUV: improve initial state for faster convergence

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For speed reason, the 'gray' plane was initialized with the same
value for 2x2 block. But in some cases (underlying camera noise, e.g.),
it could lead to instability during iteration, noise amplification,
and visible banding.
Using a precise (but slower) initialization solves the issue, and
since the convergence is faster, we might actually gain some speed.

Change-Id: I81c42101497e7096a8f60289d710f5a3bcb0ddea
This commit is contained in:
Pascal Massimino 2016-09-09 18:01:40 +02:00
parent 894232be56
commit 490ae5b13d
1 changed files with 15 additions and 9 deletions
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24
src/enc/picture_csp.c
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@ -263,7 +263,7 @@ static WEBP_INLINE void UpdateW(const fixed_y_t* src, fixed_y_t* dst, int len) {
}
static void UpdateChroma(const fixed_y_t* src1, const fixed_y_t* src2,
fixed_t* dst, fixed_y_t* tmp, int len) {
fixed_t* dst, int len) {
while (len--> 0) {
const int r = ScaleDown(src1[0], src1[3], src2[0], src2[3]);
const int g = ScaleDown(src1[1], src1[4], src2[1], src2[4]);
@ -275,10 +275,14 @@ static void UpdateChroma(const fixed_y_t* src1, const fixed_y_t* src2,
dst += 3;
src1 += 6;
src2 += 6;
if (tmp != NULL) {
tmp[0] = tmp[1] = clip_y(W);
tmp += 2;
}
}
}
static void StoreGray(const fixed_y_t* rgb, fixed_y_t* y, int len) {
int i;
for (i = 0; i < len; ++i) {
y[i] = clip_y(RGBToGray(rgb[0], rgb[1], rgb[2]));
rgb += 3;
}
}
@ -434,7 +438,7 @@ static int PreprocessARGB(const uint8_t* const r_ptr,
fixed_t* const best_uv = SAFE_ALLOC(uv_w * 3, uv_h, fixed_t);
fixed_t* const target_uv = SAFE_ALLOC(uv_w * 3, uv_h, fixed_t);
fixed_t* const best_rgb_uv = SAFE_ALLOC(uv_w * 3, 1, fixed_t);
const uint64_t diff_y_threshold = (uint64_t)(3.5 * w * h);
const uint64_t diff_y_threshold = (uint64_t)(3.0 * w * h);
int ok;
if (best_y == NULL || best_uv == NULL ||
@ -468,10 +472,12 @@ static int PreprocessARGB(const uint8_t* const r_ptr,
}
UpdateW(src1, target_y + (j + 0) * w, w);
UpdateW(src2, target_y + (j + 1) * w, w);
UpdateChroma(src1, src2, target_uv + uv_off, dst_y, uv_w);
UpdateChroma(src1, src2, target_uv + uv_off, uv_w);
memcpy(best_uv + uv_off, target_uv + uv_off, 3 * uv_w * sizeof(*best_uv));
memcpy(dst_y + w, dst_y, w * sizeof(*dst_y));
// convert two lines at a time
StoreGray(src1, dst_y, 2 * w);
}
// Iterate and resolve clipping conflicts.
for (iter = 0; iter < kNumIterations; ++iter) {
int k;
@ -491,7 +497,7 @@ static int PreprocessARGB(const uint8_t* const r_ptr,
UpdateW(src1, best_rgb_y + 0 * w, w);
UpdateW(src2, best_rgb_y + 1 * w, w);
UpdateChroma(src1, src2, best_rgb_uv, NULL, uv_w);
UpdateChroma(src1, src2, best_rgb_uv, uv_w);
// update two rows of Y and one row of RGB
for (i = 0; i < 2 * w; ++i) {