This fixes the same overflow as in the RGB48/16-bit YUV scaling;
some filters can overflow both negatively and positively (e.g.
spline/lanczos), so we bias a signed integer so it's "half signed"
and "half unsigned", and can cover overflows in both directions
while maintaining full 31-bit depth.
---
libswscale/swscale.c | 14 ++++++--------
1 files changed, 6 insertions(+), 8 deletions(-)
diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 3ea3710..c9dfc8d 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -386,8 +386,8 @@ yuv2gray16_X_c_template(SwsContext *c, const int16_t
*lumFilter,
for (i = 0; i < (dstW >> 1); i++) {
int j;
- int Y1 = 1 << 14;
- int Y2 = 1 << 14;
+ int Y1 = (1 << 14) - 0x40000000;
+ int Y2 = (1 << 14) - 0x40000000;
for (j = 0; j < lumFilterSize; j++) {
Y1 += lumSrc[j][i * 2] * lumFilter[j];
@@ -395,12 +395,10 @@ yuv2gray16_X_c_template(SwsContext *c, const int16_t
*lumFilter,
}
Y1 >>= 15;
Y2 >>= 15;
- if ((Y1 | Y2) & 0x10000) {
- Y1 = av_clip_uint16(Y1);
- Y2 = av_clip_uint16(Y2);
- }
- output_pixel(&dest[i * 2 + 0], Y1);
- output_pixel(&dest[i * 2 + 1], Y2);
+ Y1 = av_clip_int16(Y1);
+ Y2 = av_clip_int16(Y2);
+ output_pixel(&dest[i * 2 + 0], 0x8000 + Y1);
+ output_pixel(&dest[i * 2 + 1], 0x8000 + Y2);
}
}
--
1.7.2.1
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