Re: [Mesa-dev] [PATCH 2/2] st/vl: use MPEG-2 chroma cositing

Mon, 07 Oct 2013 02:59:26 -0700 

Am 01.10.2013 21:06, schrieb Grigori Goronzy:

MPEG-2 and later video standards align the chroma sample position
horizontally with the leftmost luma sample position. Add a half-texel
offset to the chroma texture sampling coordinate to sample at the
this position instead of sampling in the center between the luma
texels. This avoids minor color smearing and blurriness with most
video content.



Overall looks good to me, but one minor thing below that needs to be 
fixed first.



---
  src/gallium/auxiliary/vl/vl_compositor.c | 18 +++++++++++++++---
  1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/src/gallium/auxiliary/vl/vl_compositor.c 
b/src/gallium/auxiliary/vl/vl_compositor.c
index 4b83087..dac2c61 100644
--- a/src/gallium/auxiliary/vl/vl_compositor.c
+++ b/src/gallium/auxiliary/vl/vl_compositor.c
@@ -129,6 +129,7 @@ create_frag_shader_video_buffer(struct vl_compositor *c)
  {
     struct ureg_program *shader;
     struct ureg_src tc;
+   struct ureg_dst tc_chroma;
     struct ureg_src csc[3];
     struct ureg_src sampler[3];
     struct ureg_dst texel;
@@ -146,13 +147,18 @@ create_frag_shader_video_buffer(struct vl_compositor *c)
     }
     texel = ureg_DECL_temporary(shader);
     fragment = ureg_DECL_output(shader, TGSI_SEMANTIC_COLOR, 0);
+   tc_chroma = ureg_DECL_temporary(shader);
+
+   /* chroma offset */
+   ureg_MOV(shader, ureg_writemask(tc_chroma, TGSI_WRITEMASK_XYZW), tc);
+   ureg_ADD(shader, ureg_writemask(tc_chroma, TGSI_WRITEMASK_X), 
ureg_src(tc_chroma), ureg_scalar(tc, TGSI_SWIZZLE_Z));

  
     /*

      * texel.xyz = tex(tc, sampler[i])
      * fragment = csc * texel
      */
     for (i = 0; i < 3; ++i)
-      ureg_TEX(shader, ureg_writemask(texel, TGSI_WRITEMASK_X << i), 
TGSI_TEXTURE_2D_ARRAY, tc, sampler[i]);
+      ureg_TEX(shader, ureg_writemask(texel, TGSI_WRITEMASK_X << i), 
TGSI_TEXTURE_2D_ARRAY, i ? ureg_src(tc_chroma) : tc, sampler[i]);

  
     ureg_MOV(shader, ureg_writemask(texel, TGSI_WRITEMASK_W), ureg_imm1f(shader, 1.0f));
  
@@ -171,10 +177,12 @@ static void *

  create_frag_shader_weave(struct vl_compositor *c)
  {
     struct ureg_program *shader;
+   struct ureg_src tc;
     struct ureg_src i_tc[2];
     struct ureg_src csc[3];
     struct ureg_src sampler[3];
     struct ureg_dst t_tc[2];
+   struct ureg_dst t_tc_chroma[2];
     struct ureg_dst t_texel[2];
     struct ureg_dst o_fragment;
     unsigned i, j;
@@ -183,6 +191,7 @@ create_frag_shader_weave(struct vl_compositor *c)
     if (!shader)
        return false;

  
+   tc = ureg_DECL_fs_input(shader, TGSI_SEMANTIC_GENERIC, VS_O_VTEX, TGSI_INTERPOLATE_LINEAR);

     i_tc[0] = ureg_DECL_fs_input(shader, TGSI_SEMANTIC_GENERIC, VS_O_VTOP, 
TGSI_INTERPOLATE_LINEAR);
     i_tc[1] = ureg_DECL_fs_input(shader, TGSI_SEMANTIC_GENERIC, VS_O_VBOTTOM, 
TGSI_INTERPOLATE_LINEAR);

  
@@ -194,6 +203,7 @@ create_frag_shader_weave(struct vl_compositor *c)

     for (i = 0; i < 2; ++i) {
        t_tc[i] = ureg_DECL_temporary(shader);
        t_texel[i] = ureg_DECL_temporary(shader);
+      t_tc_chroma[i] = ureg_DECL_temporary(shader);
     }
     o_fragment = ureg_DECL_output(shader, TGSI_SEMANTIC_COLOR, 0);

  
@@ -214,6 +224,8 @@ create_frag_shader_weave(struct vl_compositor *c)

                 ureg_src(t_tc[i]), ureg_scalar(i_tc[0], TGSI_SWIZZLE_W));
        ureg_MUL(shader, ureg_writemask(t_tc[i], TGSI_WRITEMASK_Z),
                 ureg_src(t_tc[i]), ureg_scalar(i_tc[1], TGSI_SWIZZLE_W));
+      ureg_MOV(shader, ureg_writemask(t_tc_chroma[i], TGSI_WRITEMASK_XYZW), 
ureg_src(t_tc[i]));
+      ureg_ADD(shader, ureg_writemask(t_tc_chroma[i], TGSI_WRITEMASK_X), 
ureg_src(t_tc_chroma[i]), ureg_scalar(tc, TGSI_SWIZZLE_Z));
     }

  
     /* fetch the texels

@@ -223,7 +235,7 @@ create_frag_shader_weave(struct vl_compositor *c)
      */
     for (i = 0; i < 2; ++i)
        for (j = 0; j < 3; ++j) {
-         struct ureg_src src = ureg_swizzle(ureg_src(t_tc[i]),
+         struct ureg_src src = ureg_swizzle(j ? ureg_src(t_tc_chroma[i]) : 
ureg_src(t_tc[i]),
              TGSI_SWIZZLE_X, j ? TGSI_SWIZZLE_Z : TGSI_SWIZZLE_Y, 
TGSI_SWIZZLE_W, TGSI_SWIZZLE_W);

  
           ureg_TEX(shader, ureg_writemask(t_texel[i], TGSI_WRITEMASK_X << j),

@@ -586,7 +598,7 @@ calc_src_and_dst(struct vl_compositor_layer *layer, 
unsigned width, unsigned hei
     layer->src.br = calc_bottomright(size, src);
     layer->dst.tl = calc_topleft(size, dst);
     layer->dst.br = calc_bottomright(size, dst);
-   layer->zw.x = 0.0f;
+   layer->zw.x = 0.5f / size.x; /* half a texel */
     layer->zw.y = size.y;



That only works in the case of the weave and progressive shaders, cause 
I already used (abused) zw.x to selected between top/bottom bobbing in 
vl_compositor_set_buffer_layer.



Do me a favor and clean that up by renaming "zw" to "size" and adding an 
extra attribute to select between top/bottom bobbing.


Cheers,
Christian.


  }

  


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