vc1: Add avg_no_rnd_vc1_chroma_mc4_c()

Needed for proper interlaced support.
Signed-off-by: Luca Barbato <lu_zero@gentoo.org>

libavcodec/vc1dsp.c

@@ -758,6 +758,28 @@ static void avg_no_rnd_vc1_chroma_mc8_c(uint8_t *dst /* align 8 */,
     }
 }
 
+static void avg_no_rnd_vc1_chroma_mc4_c(uint8_t *dst /* align 8 */,
+                                        uint8_t *src /* align 1 */,
+                                        int stride, int h, int x, int y)
+{
+    const int A = (8 - x) * (8 - y);
+    const int B = (    x) * (8 - y);
+    const int C = (8 - x) * (    y);
+    const int D = (    x) * (    y);
+    int i;
+
+    assert(x < 8 && y < 8 && x >= 0 && y >= 0);
+
+    for (i = 0; i < h; i++) {
+        dst[0] = avg2(dst[0], chroma_mc(0));
+        dst[1] = avg2(dst[1], chroma_mc(1));
+        dst[2] = avg2(dst[2], chroma_mc(2));
+        dst[3] = avg2(dst[3], chroma_mc(3));
+        dst += stride;
+        src += stride;
+    }
+}
+
 #if CONFIG_WMV3IMAGE_DECODER || CONFIG_VC1IMAGE_DECODER
 
 static void sprite_h_c(uint8_t *dst, const uint8_t *src, int offset,
@@ -902,6 +924,7 @@ av_cold void ff_vc1dsp_init(VC1DSPContext *dsp)
     dsp->put_no_rnd_vc1_chroma_pixels_tab[0] = put_no_rnd_vc1_chroma_mc8_c;
     dsp->avg_no_rnd_vc1_chroma_pixels_tab[0] = avg_no_rnd_vc1_chroma_mc8_c;
     dsp->put_no_rnd_vc1_chroma_pixels_tab[1] = put_no_rnd_vc1_chroma_mc4_c;
+    dsp->avg_no_rnd_vc1_chroma_pixels_tab[1] = avg_no_rnd_vc1_chroma_mc4_c;
 
 #if CONFIG_WMV3IMAGE_DECODER || CONFIG_VC1IMAGE_DECODER
     dsp->sprite_h                 = sprite_h_c;