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Use the plane code and not the distance when computing statistics.

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As backward references use the plane code when checking the cost
of a distance, statistics used to compute the cost should use it too.
This provides a small compression improvement at no speed cost.

Change-Id: Icade150929ee39ef6dc0d8b1fc85973086ecf41d
This commit is contained in:
Vincent Rabaud 2017-06-01 17:08:43 +02:00
parent b903b80c30
commit f209a5481e
3 changed files with 26 additions and 8 deletions
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14
src/enc/backward_references_cost_enc.c
View File

@ -58,13 +58,21 @@ static void ConvertPopulationCountTableToBitEstimates(
}
}
static int CostModelBuild(CostModel* const m, int cache_bits,
static int CostModelBuild(CostModel* const m, int xsize, int cache_bits,
const VP8LBackwardRefs* const refs) {
int ok = 0;
VP8LRefsCursor c = VP8LRefsCursorInit(refs);
VP8LHistogram* const histo = VP8LAllocateHistogram(cache_bits);
if (histo == NULL) goto Error;
VP8LHistogramCreate(histo, refs, cache_bits);
// The following code is similar to VP8LHistogramCreate but converts the
// distance to plane code.
VP8LHistogramInit(histo, cache_bits);
while (VP8LRefsCursorOk(&c)) {
VP8LHistogramAddSinglePixOrCopy(histo, c.cur_pos, VP8LDistanceToPlaneCode,
xsize);
VP8LRefsCursorNext(&c);
}
ConvertPopulationCountTableToBitEstimates(
VP8LHistogramNumCodes(histo->palette_code_bits_),
@ -583,7 +591,7 @@ static int BackwardReferencesHashChainDistanceOnly(
if (!cc_init) goto Error;
}
if (!CostModelBuild(cost_model, cache_bits, refs)) {
if (!CostModelBuild(cost_model, xsize, cache_bits, refs)) {
goto Error;
}

14
src/enc/histogram_enc.c
View File

@ -76,7 +76,7 @@ void VP8LHistogramStoreRefs(const VP8LBackwardRefs* const refs,
VP8LHistogram* const histo) {
VP8LRefsCursor c = VP8LRefsCursorInit(refs);
while (VP8LRefsCursorOk(&c)) {
VP8LHistogramAddSinglePixOrCopy(histo, c.cur_pos);
VP8LHistogramAddSinglePixOrCopy(histo, c.cur_pos, NULL, 0);
VP8LRefsCursorNext(&c);
}
}
@ -138,7 +138,9 @@ VP8LHistogramSet* VP8LAllocateHistogramSet(int size, int cache_bits) {
// -----------------------------------------------------------------------------
void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
const PixOrCopy* const v) {
const PixOrCopy* const v,
int (*const distance_modifier)(int, int),
int distance_modifier_arg0) {
if (PixOrCopyIsLiteral(v)) {
++histo->alpha_[PixOrCopyLiteral(v, 3)];
++histo->red_[PixOrCopyLiteral(v, 2)];
@ -152,7 +154,13 @@ void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
int code, extra_bits;
VP8LPrefixEncodeBits(PixOrCopyLength(v), &code, &extra_bits);
++histo->literal_[NUM_LITERAL_CODES + code];
if (distance_modifier == NULL) {
VP8LPrefixEncodeBits(PixOrCopyDistance(v), &code, &extra_bits);
} else {
VP8LPrefixEncodeBits(
distance_modifier(distance_modifier_arg0, PixOrCopyDistance(v)),
&code, &extra_bits);
}
++histo->distance_[code];
}
}
@ -473,7 +481,7 @@ static void HistogramBuild(
while (VP8LRefsCursorOk(&c)) {
const PixOrCopy* const v = c.cur_pos;
const int ix = (y >> histo_bits) * histo_xsize + (x >> histo_bits);
VP8LHistogramAddSinglePixOrCopy(histograms[ix], v);
VP8LHistogramAddSinglePixOrCopy(histograms[ix], v, NULL, 0);
x += PixOrCopyLength(v);
while (x >= xsize) {
x -= xsize;

4
src/enc/histogram_enc.h
View File

@ -90,7 +90,9 @@ VP8LHistogram* VP8LAllocateHistogram(int cache_bits);
// Accumulate a token 'v' into a histogram.
void VP8LHistogramAddSinglePixOrCopy(VP8LHistogram* const histo,
const PixOrCopy* const v);
const PixOrCopy* const v,
int (*const distance_modifier)(int, int),
int distance_modifier_arg0);
static WEBP_INLINE int VP8LHistogramNumCodes(int palette_code_bits) {
return NUM_LITERAL_CODES + NUM_LENGTH_CODES +