H.264/SVQ3: make chroma DC work the same way as luma DC

No speed improvement, but necessary for some future stuff.
Also opens up the possibility of asm chroma dc idct/dequant.

Originally committed as revision 26349 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 22 insertions, 0 deletions

diff --git a/libavcodec/h264idct.c b/libavcodec/h264idct.c
index f5b05ac24f..53e70a22df 100644
--- a/libavcodec/h264idct.c
+++ b/libavcodec/h264idct.c
@@ -250,4 +250,26 @@ void ff_h264_luma_dc_dequant_idct_c(DCTELEM *output, DCTELEM *input, int qmul){
         output[stride* 4+offset]= ((((z1 - z2)*qmul + 128 ) >> 8));
         output[stride* 5+offset]= ((((z0 - z3)*qmul + 128 ) >> 8));
     }
+#undef stride
+}
+
+void ff_chroma_dc_dequant_idct_c(DCTELEM *output, DCTELEM *input, int qmul){
+    const int stride= 16*2;
+    const int xStride= 16;
+    int a,b,c,d,e;
+
+    a= input[0];
+    b= input[1];
+    c= input[2];
+    d= input[3];
+
+    e= a-b;
+    a= a+b;
+    b= c-d;
+    c= c+d;
+
+    output[stride*0 + xStride*0]= ((a+c)*qmul) >> 7;
+    output[stride*0 + xStride*1]= ((e+b)*qmul) >> 7;
+    output[stride*1 + xStride*0]= ((a-c)*qmul) >> 7;
+    output[stride*1 + xStride*1]= ((e-b)*qmul) >> 7;
 }