Re: [FFmpeg-devel] [PATCH v2] swscale: fix gbrap16 alpha channel issues

[Michael Niedermayer]

On Thu, Aug 03, 2017 at 04:21:54PM +0100, James Cowgill wrote:
> Fixes filter-pixfmts-scale test failing on big-endian systems due to
> alpSrc not being cast to (const int32_t**).
> 
> Also fixes distortions in the output alpha channel values by copying the
> alpha channel code from the rgba64 case found elsewhere in output.c.
> 
> Fixes ticket 6555.
> 
> Signed-off-by: James Cowgill 
> ---
>  v2
>  
>  Move declaration of A inside the loop and don't bother initializing it since
>  the initial value would never be read.

applied

thanks

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[FFmpeg-devel] [PATCH v2] swscale: fix gbrap16 alpha channel issues

[James Cowgill]

Fixes filter-pixfmts-scale test failing on big-endian systems due to
alpSrc not being cast to (const int32_t**).

Also fixes distortions in the output alpha channel values by copying the
alpha channel code from the rgba64 case found elsewhere in output.c.

Fixes ticket 6555.

Signed-off-by: James Cowgill 
---
 v2
 
 Move declaration of A inside the loop and don't bother initializing it since
 the initial value would never be read.

 libswscale/output.c | 16 
 tests/ref/fate/filter-pixfmts-scale |  4 ++--
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/libswscale/output.c b/libswscale/output.c
index 9774e9f327..f30bce8dd3 100644
--- a/libswscale/output.c
+++ b/libswscale/output.c
@@ -2026,24 +2026,24 @@ yuv2gbrp16_full_X_c(SwsContext *c, const int16_t 
*lumFilter,
 const int16_t **lumSrcx, int lumFilterSize,
 const int16_t *chrFilter, const int16_t **chrUSrcx,
 const int16_t **chrVSrcx, int chrFilterSize,
-const int16_t **alpSrc, uint8_t **dest,
+const int16_t **alpSrcx, uint8_t **dest,
 int dstW, int y)
 {
 const AVPixFmtDescriptor *desc = av_pix_fmt_desc_get(c->dstFormat);
 int i;
-int hasAlpha = (desc->flags & AV_PIX_FMT_FLAG_ALPHA) && alpSrc;
+int hasAlpha = (desc->flags & AV_PIX_FMT_FLAG_ALPHA) && alpSrcx;
 uint16_t **dest16 = (uint16_t**)dest;
 const int32_t **lumSrc  = (const int32_t**)lumSrcx;
 const int32_t **chrUSrc = (const int32_t**)chrUSrcx;
 const int32_t **chrVSrc = (const int32_t**)chrVSrcx;
-int A = 0; // init to silence warning
+const int32_t **alpSrc  = (const int32_t**)alpSrcx;
 
 for (i = 0; i < dstW; i++) {
 int j;
 int Y = -0x4000;
 int U = -(128 << 23);
 int V = -(128 << 23);
-int R, G, B;
+int R, G, B, A;
 
 for (j = 0; j < lumFilterSize; j++)
 Y += lumSrc[j][i] * (unsigned)lumFilter[j];
@@ -2059,13 +2059,13 @@ yuv2gbrp16_full_X_c(SwsContext *c, const int16_t 
*lumFilter,
 V >>= 14;
 
 if (hasAlpha) {
-A = 1 << 18;
+A = -0x4000;
 
 for (j = 0; j < lumFilterSize; j++)
 A += alpSrc[j][i] * lumFilter[j];
 
-if (A & 0xF800)
-A =  av_clip_uintp2(A, 27);
+A >>= 1;
+A += 0x20002000;
 }
 
 Y -= c->yuv2rgb_y_offset;
@@ -2083,7 +2083,7 @@ yuv2gbrp16_full_X_c(SwsContext *c, const int16_t 
*lumFilter,
 dest16[1][i] = B >> 14;
 dest16[2][i] = R >> 14;
 if (hasAlpha)
-dest16[3][i] = A >> 11;
+dest16[3][i] = av_clip_uintp2(A, 30) >> 14;
 }
 if ((!isBE(c->dstFormat)) != (!HAVE_BIGENDIAN)) {
 for (i = 0; i < dstW; i++) {
diff --git a/tests/ref/fate/filter-pixfmts-scale 
b/tests/ref/fate/filter-pixfmts-scale
index 9b601b71da..dcc34bd4d1 100644
--- a/tests/ref/fate/filter-pixfmts-scale
+++ b/tests/ref/fate/filter-pixfmts-scale
@@ -23,8 +23,8 @@ gbrap10be   6d89abb9248006c3e9017545e9474654
 gbrap10le   cf974e23f485a10740f5de74a5c8c3df
 gbrap12be   1d9b57766ba9c2192403f43967cb9af0
 gbrap12le   bb1ba1c157717db3dd612a76d38a018e
-gbrap16be   81542b96575d1fe3b239d23899f5ece3
-gbrap16le   6feb8b9da131917abe867e0eaaf07b90
+gbrap16be   c72b935a6e57a8e1c37bff08c2db55b1
+gbrap16le   13eb0e62b1ac9c1c86c81521eaefab5f
 gbrpdc3387f925f972c61aae7eb23cdc19f0
 gbrp10be0277d4c3a8498d75e2783fb81379e481
 gbrp10lef3d70f8ab845c3c9b8f7452e4a6e285a
-- 
2.13.3

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