[FFmpeg-cvslog] swscale/utils: Fix intermediate format for cascaded alpha downscaling

[Michael Niedermayer]

ffmpeg | branch: release/2.4 | Michael Niedermayer <michael at niedermayer.cc> | Thu Dec 24 21:46:15 2015 +0100| [41289bc85322a668dc4405c90b125ef2c2d5eb76] | committer: Michael Niedermayer

swscale/utils: Fix intermediate format for cascaded alpha downscaling

Fixes Ticket4926

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>
(cherry picked from commit b83d8be6bff7d645469a623aee0b380541da15cf)

Signed-off-by: Michael Niedermayer <michael at niedermayer.cc>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=41289bc85322a668dc4405c90b125ef2c2d5eb76
---

 libswscale/utils.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/libswscale/utils.c b/libswscale/utils.c
index 66d2831..6495804 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -1532,6 +1532,9 @@ fail: // FIXME replace things by appropriate error codes
         int tmpH = sqrt(srcH * (int64_t)dstH);
         enum AVPixelFormat tmpFormat = AV_PIX_FMT_YUV420P;
 
+        if (isALPHA(srcFormat))
+            tmpFormat = AV_PIX_FMT_YUVA420P;
+
         if (srcW*(int64_t)srcH <= 4LL*dstW*dstH)
             return AVERROR(EINVAL);