From: Niklas Haas <g...@haasn.dev>
We should at least bias towards the nearest integer, instead of always
rounding down, when not dithering. This is a bit more correct.
Signed-off-by: Niklas Haas <g...@haasn.dev>
Sponsored-by: Sovereign Tech Fund
---
libswscale/swscale_unscaled.c | 20 +++++++++++---------
1 file changed, 11 insertions(+), 9 deletions(-)
diff --git a/libswscale/swscale_unscaled.c b/libswscale/swscale_unscaled.c
index c7ad6b014a..ea6fb038bc 100644
--- a/libswscale/swscale_unscaled.c
+++ b/libswscale/swscale_unscaled.c
@@ -2075,17 +2075,18 @@ static int packedCopyWrapper(SwsInternal *c, const
uint8_t *const src[],
#define DITHER_COPY(dst, dstStride, src, srcStride, bswap, dbswap)\
unsigned shift= src_depth-dst_depth, tmp;\
+ unsigned bias = 1 << (shift - 1);\
if (c->opts.dither == SWS_DITHER_NONE) {\
for (i = 0; i < height; i++) {\
for (j = 0; j < length-7; j+=8) {\
- dst[j+0] = dbswap(bswap(src[j+0])>>shift);\
- dst[j+1] = dbswap(bswap(src[j+1])>>shift);\
- dst[j+2] = dbswap(bswap(src[j+2])>>shift);\
- dst[j+3] = dbswap(bswap(src[j+3])>>shift);\
- dst[j+4] = dbswap(bswap(src[j+4])>>shift);\
- dst[j+5] = dbswap(bswap(src[j+5])>>shift);\
- dst[j+6] = dbswap(bswap(src[j+6])>>shift);\
- dst[j+7] = dbswap(bswap(src[j+7])>>shift);\
+ dst[j+0] = dbswap(bswap(src[j+0] + bias))>>shift);\
+ dst[j+1] = dbswap(bswap(src[j+1] + bias))>>shift);\
+ dst[j+2] = dbswap(bswap(src[j+2] + bias))>>shift);\
+ dst[j+3] = dbswap(bswap(src[j+3] + bias))>>shift);\
+ dst[j+4] = dbswap(bswap(src[j+4] + bias))>>shift);\
+ dst[j+5] = dbswap(bswap(src[j+5] + bias))>>shift);\
+ dst[j+6] = dbswap(bswap(src[j+6] + bias))>>shift);\
+ dst[j+7] = dbswap(bswap(src[j+7] + bias))>>shift);\
}\
for (; j < length; j++) {\
dst[j] = dbswap(bswap(src[j])>>shift);\
@@ -2169,6 +2170,7 @@ static int planarCopyWrapper(SwsInternal *c, const
uint8_t *const src[],
uint16_t *dstPtr2 = (uint16_t*)dstPtr;
if (dst_depth == 8) {
+ av_assert1(src_depth > 8);
if(isBE(c->opts.src_format) == HAVE_BIGENDIAN){
DITHER_COPY(dstPtr, dstStride[plane], srcPtr2,
srcStride[plane]/2, , )
} else {
@@ -2248,7 +2250,7 @@ static int planarCopyWrapper(SwsInternal *c, const
uint8_t *const src[],
dstPtr2 += dstStride[plane]/2;
srcPtr2 += srcStride[plane]/2;
}
- } else {
+ } else { /* src_depth > dst_depth */
if(isBE(c->opts.src_format) == HAVE_BIGENDIAN){
if(isBE(c->opts.dst_format) == HAVE_BIGENDIAN){
DITHER_COPY(dstPtr2, dstStride[plane]/2, srcPtr2,
srcStride[plane]/2, , )
--
2.47.0
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