On 05/11/15 00:31, Zhao Yakui wrote:
On 11/04/2015 11:27 PM, Lionel Landwerlin wrote:
---
src/shaders/post_processing/gen7/YUV_to_RGB.g4a | 626
++++++++++++----------
src/shaders/post_processing/gen7/pl2_to_rgbx.g75b | 528
+++++++++---------
src/shaders/post_processing/gen7/pl2_to_rgbx.g7b | 528
+++++++++---------
3 files changed, 909 insertions(+), 773 deletions(-)
diff --git a/src/shaders/post_processing/gen7/YUV_to_RGB.g4a
b/src/shaders/post_processing/gen7/YUV_to_RGB.g4a
index 24616dc..6af651f 100644
--- a/src/shaders/post_processing/gen7/YUV_to_RGB.g4a
+++ b/src/shaders/post_processing/gen7/YUV_to_RGB.g4a
@@ -386,34 +386,36 @@
mov (8) fBUFFER_V(0, 0)<1> r[a0.0, 1]<16;8,2>:ub
mov (8) fBUFFER_V(1, 0)<1> r[a0.0, 17]<16;8,2>:ub
- add (16) fBUFFER_U(0, 0)<1> fBUFFER_U(0, 0)<8;8,1> -128.0f
- add (16) fBUFFER_V(0, 0)<1> fBUFFER_V(0, 0)<8;8,1> -128.0f
As far as I know, the value in fBUEER_U/V is still in [0 255] range.
So I think that it still should be extraced by 128 before it is
normalized to [0..1].
Looking at the green component for example, given the following
coefficients for Y, U and V :
CY = 1.0
CU = -0.344
CV = -0.714
This is what the current shader does :
green = ((Y + (U - 128) * CU + (V - 128) * CV) * 0.0039216) * 255
The shader in this patch does this :
green = (Y * 0.0039216 + (U * 0.0039216 - 128.0 / 255) * CU + (CV *
0.0039216 - 128.0 / 255) * CV) * 255
This looks equivalent to me given that
128.0 / 255 ~= 128 * 0.0039216
we just distribute the [0..1] normalizing factor earlier.
It's possible to do what you suggest, but it would require more
instructions.
Maybe I'm missing some precision stuff that is specific to the hardware?
+ mul (16) fBUFFER_Y(0, 0)<1> fBUFFER_Y(0,
0)<1> 0.0039216f
+ mul (16) fBUFFER_U(0, 0)<1> fBUFFER_U(0,
0)<1> 0.0039216f
+ mul (16) fBUFFER_V(0, 0)<1> fBUFFER_V(0,
0)<1> 0.0039216f
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