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Favor keeping the areas locally similar in spatial prediction mode selection

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About 0.1% compression improvement.

Change-Id: If106ab209cc2671ef282b726e09ff2971c3e4abf
This commit is contained in:
hui su 2016-10-04 16:28:24 -07:00
parent ba843a92e7
commit b34abcb8b1
1 changed files with 14 additions and 2 deletions
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16
src/enc/predictor.c
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@ -20,6 +20,7 @@
#define MAX_DIFF_COST (1e30f) #define MAX_DIFF_COST (1e30f)
static const float kSpatialPredictorBias = 15.f;
static const int kPredLowEffort = 11; static const int kPredLowEffort = 11;
static const uint32_t kMaskAlpha = 0xff000000; static const uint32_t kMaskAlpha = 0xff000000;
@ -256,7 +257,8 @@ static int GetBestPredictorForTile(int width, int height,
uint32_t* const argb_scratch, uint32_t* const argb_scratch,
const uint32_t* const argb, const uint32_t* const argb,
int max_quantization, int max_quantization,
int exact, int used_subtract_green) { int exact, int used_subtract_green,
const uint32_t* const modes) {
const int kNumPredModes = 14; const int kNumPredModes = 14;
const int start_x = tile_x << bits; const int start_x = tile_x << bits;
const int start_y = tile_y << bits; const int start_y = tile_y << bits;
@ -270,6 +272,12 @@ static int GetBestPredictorForTile(int width, int height,
// they exist. // they exist.
const int context_start_x = start_x - have_left; const int context_start_x = start_x - have_left;
const int context_width = max_x + have_left + have_right; const int context_width = max_x + have_left + have_right;
const int tiles_per_row = VP8LSubSampleSize(width, bits);
// Prediction modes of the left and above neighbor tiles.
const int left_mode = (tile_x > 0) ?
(modes[tile_y * tiles_per_row + tile_x - 1] >> 8) & 0xff : 0xff;
const int above_mode = (tile_y > 0) ?
(modes[(tile_y - 1) * tiles_per_row + tile_x] >> 8) & 0xff : 0xff;
// The width of upper_row and current_row is one pixel larger than image width // The width of upper_row and current_row is one pixel larger than image width
// to allow the top right pixel to point to the leftmost pixel of the next row // to allow the top right pixel to point to the leftmost pixel of the next row
// when at the right edge. // when at the right edge.
@ -328,6 +336,10 @@ static int GetBestPredictorForTile(int width, int height,
} }
cur_diff = PredictionCostSpatialHistogram( cur_diff = PredictionCostSpatialHistogram(
(const int (*)[256])accumulated, (const int (*)[256])histo_argb); (const int (*)[256])accumulated, (const int (*)[256])histo_argb);
// Favor keeping the areas locally similar.
if (mode == left_mode) cur_diff -= kSpatialPredictorBias;
if (mode == above_mode) cur_diff -= kSpatialPredictorBias;
if (cur_diff < best_diff) { if (cur_diff < best_diff) {
int (*tmp)[256] = histo_argb; int (*tmp)[256] = histo_argb;
histo_argb = best_histo; histo_argb = best_histo;
@ -434,7 +446,7 @@ void VP8LResidualImage(int width, int height, int bits, int low_effort,
for (tile_x = 0; tile_x < tiles_per_row; ++tile_x) { for (tile_x = 0; tile_x < tiles_per_row; ++tile_x) {
const int pred = GetBestPredictorForTile(width, height, tile_x, tile_y, const int pred = GetBestPredictorForTile(width, height, tile_x, tile_y,
bits, histo, argb_scratch, argb, max_quantization, exact, bits, histo, argb_scratch, argb, max_quantization, exact,
used_subtract_green); used_subtract_green, image);
image[tile_y * tiles_per_row + tile_x] = ARGB_BLACK | (pred << 8); image[tile_y * tiles_per_row + tile_x] = ARGB_BLACK | (pred << 8);
} }
} }