[FFmpeg-cvslog] avcodec/gdv: Eliminate 50% of the reads in the first inner loop in rescale()

[Michael Niedermayer]

ffmpeg | branch: master | Michael Niedermayer <michael at niedermayer.cc> | Sun Aug  5 17:06:44 2018 +0200| [5f84fbce08769fb21d8459b81e9aad53635008b7] | committer: Michael Niedermayer

avcodec/gdv: Eliminate 50% of the reads in the first inner loop in rescale()

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

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=5f84fbce08769fb21d8459b81e9aad53635008b7
---

 libavcodec/gdv.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/libavcodec/gdv.c b/libavcodec/gdv.c
index 595d8ff4e4..aea15a88ef 100644
--- a/libavcodec/gdv.c
+++ b/libavcodec/gdv.c
@@ -85,9 +85,15 @@ static void rescale(GDVContext *gdv, uint8_t *dst, int w, int h, int scale_v, in
             int y = h - j - 1;
             uint8_t *dst1 = dst + PREAMBLE_SIZE + y * w;
             uint8_t *src1 = dst + PREAMBLE_SIZE + (y>>!!gdv->scale_h) * (w>>1);
-            for (x = w - 1; x >= 0; x--) {
+
+            for (x = w - 1; x >= 0 && !(x&1); x--) {
                 dst1[x] = src1[(x>>1)];
             }
+
+            for (x--; x >= 0; x-=2) {
+                dst1[x  ] =
+                dst1[x+1] = src1[(x>>1)];
+            }
         }
     } else if (gdv->scale_h) {
         for (j = 0; j < h; j++) {