[FFmpeg-devel] [PATCH v2 1/3] swscale/loongarch: fix LASX YUV2RGB residual for multi-row slices

[David Christle via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

The res variable (pixel residual count for widths not divisible by 16)
is computed once before the row loop, but DEALYUV2RGBLINERES and
DEALYUV2RGBLINERES32 destructively subtract 8 from it inside the loop
body. When srcSliceH > 2, subsequent row pairs get an incorrect
residual count, producing wrong output for the tail pixels.

Fix by recomputing res from the constant c->opts.dst_w at the top of
each row-pair iteration.

Signed-off-by: David Christle <dev@christle.is>
---
 libswscale/loongarch/yuv2rgb_lasx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/libswscale/loongarch/yuv2rgb_lasx.c b/libswscale/loongarch/yuv2rgb_lasx.c
index 9032887ff8..d08cf10d4b 100644
--- a/libswscale/loongarch/yuv2rgb_lasx.c
+++ b/libswscale/loongarch/yuv2rgb_lasx.c
@@ -185,6 +185,7 @@
         const uint8_t *py_2 = py_1   +                   srcStride[0];              \
         const uint8_t *pu   = src[1] +   (y >> vshift) * srcStride[1];              \
         const uint8_t *pv   = src[2] +   (y >> vshift) * srcStride[2];              \
+        res = c->opts.dst_w & 15;                                                   \
         for(x = 0; x < h_size; x++) {                                               \
 
 #define YUV2RGBFUNC32(func_name, dst_type, alpha)                                   \
@@ -213,6 +214,7 @@
         const uint8_t *py_2 = py_1   +                   srcStride[0];              \
         const uint8_t *pu   = src[1] +   (y >> vshift) * srcStride[1];              \
         const uint8_t *pv   = src[2] +   (y >> vshift) * srcStride[2];              \
+        res = c->opts.dst_w & 15;                                                   \
         for(x = 0; x < h_size; x++) {                                               \
 
 #define DEALYUV2RGBLINE                                                             \
-- 
2.52.0


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