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use DC error diffusion for U/V at low-quality

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This fixes some color smearing due to heavy quantization.
This is only enabled for q <= 30 (cf ERROR_DIFFUSION_QUALITY)

Change-Id: I07e83a4d38461357a32c9e214f7eadc6db73baa9
This commit is contained in:
Pascal Massimino
2017-12-11 05:07:13 -08:00
parent 1c59020b93
commit 96bf07c560
5 changed files with 106 additions and 3 deletions
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8
src/enc/iterator_enc.c
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@ -26,6 +26,9 @@ static void InitLeft(VP8EncIterator* const it) {
memset(it->u_left_, 129, 8);
memset(it->v_left_, 129, 8);
it->left_nz_[8] = 0;
if (it->top_derr_ != NULL) {
memset(&it->left_derr_, 0, sizeof(it->left_derr_));
}
}
static void InitTop(VP8EncIterator* const it) {
@ -33,6 +36,9 @@ static void InitTop(VP8EncIterator* const it) {
const size_t top_size = enc->mb_w_ * 16;
memset(enc->y_top_, 127, 2 * top_size);
memset(enc->nz_, 0, enc->mb_w_ * sizeof(*enc->nz_));
if (enc->top_derr_ != NULL) {
memset(enc->top_derr_, 0, enc->mb_w_ * sizeof(*enc->top_derr_));
}
}
void VP8IteratorSetRow(VP8EncIterator* const it, int y) {
@ -76,6 +82,7 @@ void VP8IteratorInit(VP8Encoder* const enc, VP8EncIterator* const it) {
it->y_left_ = (uint8_t*)WEBP_ALIGN(it->yuv_left_mem_ + 1);
it->u_left_ = it->y_left_ + 16 + 16;
it->v_left_ = it->u_left_ + 16;
it->top_derr_ = enc->top_derr_;
VP8IteratorReset(it);
}
@ -450,4 +457,3 @@ int VP8IteratorRotateI4(VP8EncIterator* const it,
}
//------------------------------------------------------------------------------