From: Niklas Haas <g...@haasn.dev> The current logic uses 12-bit linear light math, which is woefully insufficient and leads to nasty postarization artifacts. This patch simply switches the internal logic to 16-bit precision.
This raises the memory requirement of these tables from 32 kB to 272 kB. Fixes: ticket 4829 Signed-off-by: Niklas Haas <g...@haasn.dev> Sponsored-by: Sovereign Tech Fund --- libswscale/swscale.c | 16 ++++++++-------- libswscale/swscale_internal.h | 8 ++++---- libswscale/utils.c | 19 ++++++++++++------- 3 files changed, 24 insertions(+), 19 deletions(-) diff --git a/libswscale/swscale.c b/libswscale/swscale.c index 96634acfd6..da3a082905 100644 --- a/libswscale/swscale.c +++ b/libswscale/swscale.c @@ -773,10 +773,10 @@ void ff_xyz12Torgb48(const SwsInternal *c, uint8_t *dst, int dst_stride, c->xyz2rgb_matrix[2][1] * y + c->xyz2rgb_matrix[2][2] * z >> 12; - // limit values to 12-bit depth - r = av_clip_uintp2(r, 12); - g = av_clip_uintp2(g, 12); - b = av_clip_uintp2(b, 12); + // limit values to 16-bit depth + r = av_clip_uint16(r); + g = av_clip_uint16(g); + b = av_clip_uint16(b); // convert from sRGBlinear to RGB and scale from 12bit to 16bit if (desc->flags & AV_PIX_FMT_FLAG_BE) { @@ -832,10 +832,10 @@ void ff_rgb48Toxyz12(const SwsInternal *c, uint8_t *dst, int dst_stride, c->rgb2xyz_matrix[2][1] * g + c->rgb2xyz_matrix[2][2] * b >> 12; - // limit values to 12-bit depth - x = av_clip_uintp2(x, 12); - y = av_clip_uintp2(y, 12); - z = av_clip_uintp2(z, 12); + // limit values to 16-bit depth + x = av_clip_uint16(x); + y = av_clip_uint16(y); + z = av_clip_uint16(z); // convert from XYZlinear to X'Y'Z' and scale from 12bit to 16bit if (desc->flags & AV_PIX_FMT_FLAG_BE) { diff --git a/libswscale/swscale_internal.h b/libswscale/swscale_internal.h index 768e394560..5acd277b50 100644 --- a/libswscale/swscale_internal.h +++ b/libswscale/swscale_internal.h @@ -547,10 +547,10 @@ struct SwsInternal { /* pre defined color-spaces gamma */ #define XYZ_GAMMA (2.6f) #define RGB_GAMMA (2.2f) - int16_t *xyzgamma; - int16_t *rgbgamma; - int16_t *xyzgammainv; - int16_t *rgbgammainv; + uint16_t *xyzgamma; + uint16_t *rgbgamma; + uint16_t *xyzgammainv; + uint16_t *rgbgammainv; int16_t xyz2rgb_matrix[3][4]; int16_t rgb2xyz_matrix[3][4]; diff --git a/libswscale/utils.c b/libswscale/utils.c index 4dedbfc394..937e19f651 100644 --- a/libswscale/utils.c +++ b/libswscale/utils.c @@ -948,7 +948,8 @@ static void fill_xyztables(SwsInternal *c) {1689, 1464, 739}, { 871, 2929, 296}, { 79, 488, 3891} }; - static int16_t xyzgamma_tab[4096], rgbgamma_tab[4096], xyzgammainv_tab[4096], rgbgammainv_tab[4096]; + static uint16_t xyzgamma_tab[4096], rgbgammainv_tab[4096]; + static uint16_t rgbgamma_tab[65536], xyzgammainv_tab[65536]; memcpy(c->xyz2rgb_matrix, xyz2rgb_matrix, sizeof(c->xyz2rgb_matrix)); memcpy(c->rgb2xyz_matrix, rgb2xyz_matrix, sizeof(c->rgb2xyz_matrix)); @@ -957,15 +958,19 @@ static void fill_xyztables(SwsInternal *c) c->xyzgammainv = xyzgammainv_tab; c->rgbgammainv = rgbgammainv_tab; - if (rgbgamma_tab[4095]) + if (xyzgamma_tab[4095]) return; - /* set gamma vectors */ + /* set input gamma vectors */ for (i = 0; i < 4096; i++) { - xyzgamma_tab[i] = lrint(pow(i / 4095.0, xyzgamma) * 4095.0); - rgbgamma_tab[i] = lrint(pow(i / 4095.0, rgbgamma) * 4095.0); - xyzgammainv_tab[i] = lrint(pow(i / 4095.0, xyzgammainv) * 4095.0); - rgbgammainv_tab[i] = lrint(pow(i / 4095.0, rgbgammainv) * 4095.0); + xyzgamma_tab[i] = lrint(pow(i / 4095.0, xyzgamma) * 65535.0); + rgbgammainv_tab[i] = lrint(pow(i / 4095.0, rgbgammainv) * 65535.0); + } + + /* set output gamma vectors */ + for (i = 0; i < 65536; i++) { + rgbgamma_tab[i] = lrint(pow(i / 65535.0, rgbgamma) * 4095.0); + xyzgammainv_tab[i] = lrint(pow(i / 65535.0, xyzgammainv) * 4095.0); } } -- 2.47.0 _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".