Message ID | 20200120192043.4288-2-andreas.rheinhardt@gmail.com |
---|---|
State | Accepted |
Headers | show |
Series | [FFmpeg-devel,1/2] avcodec/adxenc: Avoid undefined left shift of negative numbers | expand |
Context | Check | Description |
---|---|---|
andriy/ffmpeg-patchwork | success | Make fate finished |
diff --git a/libavcodec/adxdec.c b/libavcodec/adxdec.c index 178ea99dcf..40ed8e5ba7 100644 --- a/libavcodec/adxdec.c +++ b/libavcodec/adxdec.c @@ -81,7 +81,7 @@ static int adx_decode(ADXContext *c, int16_t *out, int offset, s2 = prev->s2; for (i = 0; i < BLOCK_SAMPLES; i++) { d = get_sbits(&gb, 4); - s0 = ((d * (1 << COEFF_BITS)) * scale + c->coeff[0] * s1 + c->coeff[1] * s2) >> COEFF_BITS; + s0 = d * scale + ((c->coeff[0] * s1 + c->coeff[1] * s2) >> COEFF_BITS); s2 = s1; s1 = av_clip_int16(s0); *out++ = s1;
Replace "(a * (1 << shift) * b + c) >> shift" by "a * b + (c >> shift)". It is equivalent to the old code because a is in the range of uint16_t, shift is 12 and b is effectively a signed 4-bit number, so that no overflow/truncation of high bits happens during the multiplication (overflow would be undefined anyway). Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com> --- libavcodec/adxdec.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)