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swscale/output: fix bilinear yuv2rgb chroma interpolation

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These functions were divided into two special cases; one assuming that
uvalpha == 0, and the other assuming that uvalpha == 2048. This worked fine
for simple 2x chroma upscaling but broke for e.g. yuv410p, non-centered chroma,
or other special cases that involved non-aligned chroma filters.

Fix it by instead dividing this check into two cases, a uvalpha==0 fast path
and a uvalpha>0 general path. Instead of (A+B)/2 the general path now multiplies
in the true uvalpha weight.

I tried preserving the old fast path for the case of uvalpha == 2048, but this
was significantly slower in practise versus having just one general path.
However, we still need a uvalpha == 0 path for the unscaled case.

Fixes: ticket #5083
Signed-off-by: Niklas Haas <git@haasn.dev>
Sponsored-by: Sovereign Tech Fund
This commit is contained in:
Niklas Haas 2024-12-17 13:23:14 +01:00
parent 6b31e42c47
commit 095f8038fa
1 changed files with 24 additions and 12 deletions
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36
libswscale/output.c
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@ -1206,7 +1206,7 @@ yuv2rgba64_1_c_template(SwsInternal *c, const int32_t *buf0,
int i;
int A1 = 0xffff<<14, A2= 0xffff<<14;
if (uvalpha < 2048) {
if (uvalpha == 0) {
for (i = 0; i < ((dstW + 1) >> 1); i++) {
SUINT Y1 = (buf0[i * 2] ) >> 2;
SUINT Y2 = (buf0[i * 2 + 1]) >> 2;
@ -1253,11 +1253,14 @@ yuv2rgba64_1_c_template(SwsInternal *c, const int32_t *buf0,
} else {
const int32_t *ubuf1 = ubuf[1], *vbuf1 = vbuf[1];
int A1 = 0xffff<<14, A2 = 0xffff<<14;
int uvalpha1 = 4096 - uvalpha;
av_assert2(uvalpha <= 4096U);
for (i = 0; i < ((dstW + 1) >> 1); i++) {
SUINT Y1 = (buf0[i * 2] ) >> 2;
SUINT Y2 = (buf0[i * 2 + 1]) >> 2;
int U = (ubuf0[i] + ubuf1[i] - (128 << 12)) >> 3;
int V = (vbuf0[i] + vbuf1[i] - (128 << 12)) >> 3;
int U = (ubuf0[i] * uvalpha1 + ubuf1[i] * uvalpha - (128 << 23)) >> 14;
int V = (vbuf0[i] * uvalpha1 + vbuf1[i] * uvalpha - (128 << 23)) >> 14;
int R, G, B;
Y1 -= c->yuv2rgb_y_offset;
@ -1428,7 +1431,7 @@ yuv2rgba64_full_1_c_template(SwsInternal *c, const int32_t *buf0,
int i;
int A = 0xffff<<14;
if (uvalpha < 2048) {
if (uvalpha == 0) {
for (i = 0; i < dstW; i++) {
SUINT Y = (buf0[i]) >> 2;
int U = (ubuf0[i] - (128 << 11)) >> 2;
@ -1461,11 +1464,14 @@ yuv2rgba64_full_1_c_template(SwsInternal *c, const int32_t *buf0,
}
} else {
const int32_t *ubuf1 = ubuf[1], *vbuf1 = vbuf[1];
int uvalpha1 = 4096 - uvalpha;
int A = 0xffff<<14;
av_assert2(uvalpha <= 4096U);
for (i = 0; i < dstW; i++) {
SUINT Y = (buf0[i] ) >> 2;
int U = (ubuf0[i] + ubuf1[i] - (128 << 12)) >> 3;
int V = (vbuf0[i] + vbuf1[i] - (128 << 12)) >> 3;
int U = (ubuf0[i] * uvalpha1 + ubuf1[i] * uvalpha - (128 << 23)) >> 14;
int V = (vbuf0[i] * uvalpha1 + vbuf1[i] * uvalpha - (128 << 23)) >> 14;
int R, G, B;
Y -= c->yuv2rgb_y_offset;
@ -1813,7 +1819,7 @@ yuv2rgb_1_c_template(SwsInternal *c, const int16_t *buf0,
const int16_t *ubuf0 = ubuf[0], *vbuf0 = vbuf[0];
int i;
if (uvalpha < 2048) {
if (uvalpha == 0) {
for (i = 0; i < ((dstW + 1) >> 1); i++) {
int Y1 = (buf0[i * 2 ] + 64) >> 7;
int Y2 = (buf0[i * 2 + 1] + 64) >> 7;
@ -1836,11 +1842,14 @@ yuv2rgb_1_c_template(SwsInternal *c, const int16_t *buf0,
}
} else {
const int16_t *ubuf1 = ubuf[1], *vbuf1 = vbuf[1];
int uvalpha1 = 4096 - uvalpha;
av_assert2(uvalpha <= 4096U);
for (i = 0; i < ((dstW + 1) >> 1); i++) {
int Y1 = (buf0[i * 2 ] + 64) >> 7;
int Y2 = (buf0[i * 2 + 1] + 64) >> 7;
int U = (ubuf0[i] + ubuf1[i] + 128) >> 8;
int V = (vbuf0[i] + vbuf1[i] + 128) >> 8;
int U = (ubuf0[i] * uvalpha1 + ubuf1[i] * uvalpha + (128 << 11)) >> 19;
int V = (vbuf0[i] * uvalpha1 + vbuf1[i] * uvalpha + (128 << 11)) >> 19;
int A1, A2;
const void *r = c->table_rV[V + YUVRGB_TABLE_HEADROOM],
*g = (c->table_gU[U + YUVRGB_TABLE_HEADROOM] + c->table_gV[V + YUVRGB_TABLE_HEADROOM]),
@ -2189,7 +2198,7 @@ yuv2rgb_full_1_c_template(SwsInternal *c, const int16_t *buf0,
|| target == AV_PIX_FMT_BGR8 || target == AV_PIX_FMT_RGB8)
step = 1;
if (uvalpha < 2048) {
if (uvalpha == 0) {
int A = 0; //init to silence warning
for (i = 0; i < dstW; i++) {
int Y = buf0[i] * 4;
@ -2208,10 +2217,13 @@ yuv2rgb_full_1_c_template(SwsInternal *c, const int16_t *buf0,
} else {
const int16_t *ubuf1 = ubuf[1], *vbuf1 = vbuf[1];
int A = 0; //init to silence warning
int uvalpha1 = 4096 - uvalpha;
av_assert2(uvalpha <= 4096U);
for (i = 0; i < dstW; i++) {
int Y = buf0[i] * 4;
int U = (ubuf0[i] + ubuf1[i] - (128<<8)) * 2;
int V = (vbuf0[i] + vbuf1[i] - (128<<8)) * 2;
int U = (ubuf0[i] * uvalpha1 + ubuf1[i] * uvalpha - (128 << 19)) >> 10;
int V = (vbuf0[i] * uvalpha1 + vbuf1[i] * uvalpha - (128 << 19)) >> 10;
if (hasAlpha) {
A = (abuf0[i] + 64) >> 7;