[FFmpeg-devel] [PATCH] checkasm/hevc_deblock: adjust RANDCLIP to clip after rng()

[Stone Chen]

Increase chances of generating a strong deblock test case by changing RANDCLIP to generate the random value first before clipping.

RANDCLIP(x, diff) attempts to generate a random value such the distance to x is less than diff. This is also clipped to the pixel range. This is done by subtracting diff from x and adding a random value between 0 and 2*diff. However since this occurs after clipping, if e.g. x - diff is negative, then it's possible to exceed the diff. Instead generate the number first and then clip.

Signed-off-by: Stone Chen <chen.stonechen at gmail.com>
---
 tests/checkasm/hevc_deblock.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/checkasm/hevc_deblock.c b/tests/checkasm/hevc_deblock.c
index 89dd8a308b..46faf34c2d 100644
--- a/tests/checkasm/hevc_deblock.c
+++ b/tests/checkasm/hevc_deblock.c
@@ -104,8 +104,8 @@ static void check_deblock_chroma(HEVCDSPContext *h, int bit_depth, int c)
     else \
         *(uint16_t*)(&x) = z; \
 } while (0)
-#define RANDCLIP(x, diff) av_clip(GET(x) - (diff), 0, \
-    (1 << (bit_depth)) - 1) + rnd() % FFMAX(2 * (diff), 1)
+#define RANDCLIP(x, diff) av_clip(GET(x) - (diff) + rnd() % FFMAX(2 * (diff), 1), 0, \
+    (1 << (bit_depth)) - 1)
 
 // NOTE: this function doesn't work 'correctly' in that it won't always choose
 // strong/strong or weak/weak, in most cases it tends to but will sometimes mix
-- 
2.47.1.windows.1