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| author | Ronald S. Bultje <rsbultje@gmail.com> | 2011-12-16 00:03:54 +0000 |
|---|---|---|
| committer | Mans Rullgard <mans@mansr.com> | 2011-12-17 18:36:20 +0000 |
| commit | be1bafc303a77fa9ca5a99e36a65d5765012d3f4 (patch) | |
| tree | 6e7daa2b038cb79f72f8d0fc4ef04756eebad93d /libswscale/swscale.c | |
| parent | 5d8122db5c0b537c4d2c3352b4c89cb92f865bc2 (diff) | |
| download | ffmpeg-be1bafc303a77fa9ca5a99e36a65d5765012d3f4.tar.gz | |
swscale: fix overflows in output of RGB48 pixels.
For certain types of filters where the intermediate sum of coefficients
can go above the fixed-point equivalent of 1.0 in the middle of a filter,
the sum of a 31-bit calculation can overflow in both directions and can
thus not be represented in a 32-bit signed or unsigned integer. To work
around this, we subtract 0x40000000 from a signed integer base, so that
we're halfway signed/unsigned, which makes it fit even if it overflows.
After the filter finishes, we add the scaled bias back after a shift.
We use the same trick for 16-bit bpc YUV output routines.
Signed-off-by: Mans Rullgard <mans@mansr.com>
Diffstat (limited to 'libswscale/swscale.c')
| -rw-r--r-- | libswscale/swscale.c | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/libswscale/swscale.c b/libswscale/swscale.c index f072378001..818c049f35 100644 --- a/libswscale/swscale.c +++ b/libswscale/swscale.c @@ -754,8 +754,8 @@ yuv2rgb48_X_c_template(SwsContext *c, const int16_t *lumFilter, for (i = 0; i < (dstW >> 1); i++) { int j; - int Y1 = 0; - int Y2 = 0; + int Y1 = -0x40000000; + int Y2 = -0x40000000; int U = -128 << 23; // 19 int V = -128 << 23; int R, G, B; @@ -771,7 +771,9 @@ yuv2rgb48_X_c_template(SwsContext *c, const int16_t *lumFilter, // 8bit: 12+15=27; 16-bit: 12+19=31 Y1 >>= 14; // 10 + Y1 += 0x10000; Y2 >>= 14; + Y2 += 0x10000; U >>= 14; V >>= 14; |