On Tue, 17 Dec 2024 15:35:22 +0100 Niklas Haas <ffm...@haasn.xyz> wrote:
> 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
Ignore this one, it's wrong. I forgot to amend my local changes before sending
the patch. Will send a v3.
> ---
> 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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