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swscale/rgb2rgb: improve chroma conversion in ff_rgb24toyv12_c

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The current code subsamples by dropping 3/4 pixels to calculate the
chroma components. This commit calculates the average of 4 rgb pixels
before calculating the chroma components, putting it in line with the
mmxext implementation.
This commit is contained in:
Ramiro Polla 2024-08-28 19:51:55 +02:00
parent d8848325a6
commit 3604b2403c
2 changed files with 37 additions and 45 deletions
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2
libswscale/rgb2rgb.h
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@ -121,8 +121,6 @@ extern void (*yuv422ptouyvy)(const uint8_t *ysrc, const uint8_t *usrc, const uin
/**
* Height should be a multiple of 2 and width should be a multiple of 2.
* (If this is a problem for anyone then tell me, and I will fix it.)
* Chrominance data is only taken from every second line, others are ignored.
* FIXME: Write high quality version.
*/
extern void (*ff_rgb24toyv12)(const uint8_t *src, uint8_t *ydst, uint8_t *udst, uint8_t *vdst,
int width, int height,

80
libswscale/rgb2rgb_template.c
View File

@ -642,9 +642,6 @@ static inline void uyvytoyv12_c(const uint8_t *src, uint8_t *ydst,
/**
* Height should be a multiple of 2 and width should be a multiple of 2.
* (If this is a problem for anyone then tell me, and I will fix it.)
* Chrominance data is only taken from every second line,
* others are ignored in the C version.
* FIXME: Write HQ version.
*/
void ff_rgb24toyv12_c(const uint8_t *src, uint8_t *ydst, uint8_t *udst,
uint8_t *vdst, int width, int height, int lumStride,
@ -655,55 +652,52 @@ void ff_rgb24toyv12_c(const uint8_t *src, uint8_t *ydst, uint8_t *udst,
int32_t rv = rgb2yuv[RV_IDX], gv = rgb2yuv[GV_IDX], bv = rgb2yuv[BV_IDX];
int y;
const int chromWidth = width >> 1;
const uint8_t *src1 = src;
const uint8_t *src2 = src1 + srcStride;
uint8_t *ydst1 = ydst;
uint8_t *ydst2 = ydst + lumStride;
for (y = 0; y < height; y += 2) {
int i;
for (i = 0; i < chromWidth; i++) {
unsigned int b = src[6 * i + 0];
unsigned int g = src[6 * i + 1];
unsigned int r = src[6 * i + 2];
unsigned int b11 = src1[6 * i + 0];
unsigned int g11 = src1[6 * i + 1];
unsigned int r11 = src1[6 * i + 2];
unsigned int b12 = src1[6 * i + 3];
unsigned int g12 = src1[6 * i + 4];
unsigned int r12 = src1[6 * i + 5];
unsigned int b21 = src2[6 * i + 0];
unsigned int g21 = src2[6 * i + 1];
unsigned int r21 = src2[6 * i + 2];
unsigned int b22 = src2[6 * i + 3];
unsigned int g22 = src2[6 * i + 4];
unsigned int r22 = src2[6 * i + 5];
unsigned int Y = ((ry * r + gy * g + by * b) >> RGB2YUV_SHIFT) + 16;
unsigned int V = ((rv * r + gv * g + bv * b) >> RGB2YUV_SHIFT) + 128;
unsigned int U = ((ru * r + gu * g + bu * b) >> RGB2YUV_SHIFT) + 128;
unsigned int Y11 = ((ry * r11 + gy * g11 + by * b11) >> RGB2YUV_SHIFT) + 16;
unsigned int Y12 = ((ry * r12 + gy * g12 + by * b12) >> RGB2YUV_SHIFT) + 16;
unsigned int Y21 = ((ry * r21 + gy * g21 + by * b21) >> RGB2YUV_SHIFT) + 16;
unsigned int Y22 = ((ry * r22 + gy * g22 + by * b22) >> RGB2YUV_SHIFT) + 16;
udst[i] = U;
vdst[i] = V;
ydst[2 * i] = Y;
unsigned int bx = (b11 + b12 + b21 + b22) >> 2;
unsigned int gx = (g11 + g12 + g21 + g22) >> 2;
unsigned int rx = (r11 + r12 + r21 + r22) >> 2;
b = src[6 * i + 3];
g = src[6 * i + 4];
r = src[6 * i + 5];
unsigned int U = ((ru * rx + gu * gx + bu * bx) >> RGB2YUV_SHIFT) + 128;
unsigned int V = ((rv * rx + gv * gx + bv * bx) >> RGB2YUV_SHIFT) + 128;
Y = ((ry * r + gy * g + by * b) >> RGB2YUV_SHIFT) + 16;
ydst[2 * i + 1] = Y;
ydst1[2 * i + 0] = Y11;
ydst1[2 * i + 1] = Y12;
ydst2[2 * i + 0] = Y21;
ydst2[2 * i + 1] = Y22;
udst[i] = U;
vdst[i] = V;
}
ydst += lumStride;
src += srcStride;
if (y+1 == height)
break;
for (i = 0; i < chromWidth; i++) {
unsigned int b = src[6 * i + 0];
unsigned int g = src[6 * i + 1];
unsigned int r = src[6 * i + 2];
unsigned int Y = ((ry * r + gy * g + by * b) >> RGB2YUV_SHIFT) + 16;
ydst[2 * i] = Y;
b = src[6 * i + 3];
g = src[6 * i + 4];
r = src[6 * i + 5];
Y = ((ry * r + gy * g + by * b) >> RGB2YUV_SHIFT) + 16;
ydst[2 * i + 1] = Y;
}
udst += chromStride;
vdst += chromStride;
ydst += lumStride;
src += srcStride;
src1 += srcStride * 2;
src2 += srcStride * 2;
ydst1 += lumStride * 2;
ydst2 += lumStride * 2;
udst += chromStride;
vdst += chromStride;
}
}