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simplify the Histogram struct, to only store max_value and last_nz

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we don't need to store the whole distribution in order to compute the alpha

Later, we can incorporate the max_value / last_non_zero bookkeeping
in SSE2 directly.

Change-Id: I748ccea4ac17965d7afcab91845ef01be3aa3e15
This commit is contained in:
Pascal Massimino
2014-12-10 10:44:57 +01:00
parent 37e395fd1c
commit bad775715a
6 changed files with 59 additions and 33 deletions
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20
src/dsp/enc.c
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@ -40,10 +40,27 @@ const int VP8DspScan[16 + 4 + 4] = {
8 + 0 * BPS, 12 + 0 * BPS, 8 + 4 * BPS, 12 + 4 * BPS // V
};
// general-purpose util function
void VP8LSetHistogramData(const int distribution[MAX_COEFF_THRESH + 1],
VP8Histogram* const histo) {
int max_value = 0, last_non_zero = 1;
int k;
for (k = 0; k <= MAX_COEFF_THRESH; ++k) {
const int value = distribution[k];
if (value > 0) {
if (value > max_value) max_value = value;
last_non_zero = k;
}
}
histo->max_value = max_value;
histo->last_non_zero = last_non_zero;
}
static void CollectHistogram(const uint8_t* ref, const uint8_t* pred,
int start_block, int end_block,
VP8Histogram* const histo) {
int j;
int distribution[MAX_COEFF_THRESH + 1] = { 0 };
for (j = start_block; j < end_block; ++j) {
int k;
int16_t out[16];
@ -54,9 +71,10 @@ static void CollectHistogram(const uint8_t* ref, const uint8_t* pred,
for (k = 0; k < 16; ++k) {
const int v = abs(out[k]) >> 3; // TODO(skal): add rounding?
const int clipped_value = clip_max(v, MAX_COEFF_THRESH);
histo->distribution[clipped_value]++;
++distribution[clipped_value];
}
}
VP8LSetHistogramData(distribution, histo);
}
//------------------------------------------------------------------------------