| Index: libvpx/source/libvpx/vp8/common/x86/idctllm_mmx.asm
|
| diff --git a/libvpx/source/libvpx/vp8/common/x86/idctllm_mmx.asm b/libvpx/source/libvpx/vp8/common/x86/idctllm_mmx.asm
|
| index 465626b8fa3d1e7be91476a8eb43dbd677cc9929..43735bc4b6f41521acdc42b0b75a9a91329c9e3a 100644
|
| --- a/libvpx/source/libvpx/vp8/common/x86/idctllm_mmx.asm
|
| +++ b/libvpx/source/libvpx/vp8/common/x86/idctllm_mmx.asm
|
| @@ -14,18 +14,18 @@
|
| ; /****************************************************************************
|
| ; * Notes:
|
| ; *
|
| -; * This implementation makes use of 16 bit fixed point version of two multiply
|
| +; * This implementation makes use of 16 bit fixed point verio of two multiply
|
| ; * constants:
|
| ; * 1. sqrt(2) * cos (pi/8)
|
| -; * 2. sqrt(2) * sin (pi/8)
|
| -; * Because the first constant is bigger than 1, to maintain the same 16 bit
|
| -; * fixed point precision as the second one, we use a trick of
|
| +; * 2. sqrt(2) * sin (pi/8)
|
| +; * Becuase the first constant is bigger than 1, to maintain the same 16 bit
|
| +; * fixed point prrcision as the second one, we use a trick of
|
| ; * x * a = x + x*(a-1)
|
| ; * so
|
| ; * x * sqrt(2) * cos (pi/8) = x + x * (sqrt(2) *cos(pi/8)-1).
|
| ; *
|
| -; * For the second constant, because of the 16bit version is 35468, which
|
| -; * is bigger than 32768, in signed 16 bit multiply, it becomes a negative
|
| +; * For the second constant, becuase of the 16bit version is 35468, which
|
| +; * is bigger than 32768, in signed 16 bit multiply, it become a negative
|
| ; * number.
|
| ; * (x * (unsigned)35468 >> 16) = x * (signed)35468 >> 16 + x
|
| ; *
|
|
|