Strong filtering function for future RV40 loop filter

Originally committed as revision 15918 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/rv40.c

@@ -285,6 +285,110 @@ static inline void rv40_weak_loop_filter(uint8_t *src, const int step,
     }
 }
 
+static inline void rv40_adaptive_loop_filter(uint8_t *src, const int step,
+                                             const int stride, const int dmode,
+                                             const int lim_q1, const int lim_p1,
+                                             const int alpha,
+                                             const int beta, const int beta2,
+                                             const int chroma, const int edge)
+{
+    int diff_p1p0[4], diff_q1q0[4], diff_p1p2[4], diff_q1q2[4];
+    int sum_p1p0 = 0, sum_q1q0 = 0, sum_p1p2 = 0, sum_q1q2 = 0;
+    uint8_t *ptr;
+    int flag_strong0 = 1, flag_strong1 = 1;
+    int filter_p1, filter_q1;
+    int i;
+    int lims;
+
+    for(i = 0, ptr = src; i < 4; i++, ptr += stride){
+        diff_p1p0[i] = ptr[-2*step] - ptr[-1*step];
+        diff_q1q0[i] = ptr[ 1*step] - ptr[ 0*step];
+        sum_p1p0 += diff_p1p0[i];
+        sum_q1q0 += diff_q1q0[i];
+    }
+    filter_p1 = FFABS(sum_p1p0) < (beta<<2);
+    filter_q1 = FFABS(sum_q1q0) < (beta<<2);
+    if(!filter_p1 && !filter_q1)
+        return;
+
+    for(i = 0, ptr = src; i < 4; i++, ptr += stride){
+        diff_p1p2[i] = ptr[-2*step] - ptr[-3*step];
+        diff_q1q2[i] = ptr[ 1*step] - ptr[ 2*step];
+        sum_p1p2 += diff_p1p2[i];
+        sum_q1q2 += diff_q1q2[i];
+    }
+
+    if(edge){
+        flag_strong0 = filter_p1 && (FFABS(sum_p1p2) < beta2);
+        flag_strong1 = filter_q1 && (FFABS(sum_q1q2) < beta2);
+    }else{
+        flag_strong0 = flag_strong1 = 0;
+    }
+
+    lims = filter_p1 + filter_q1 + ((lim_q1 + lim_p1) >> 1) + 1;
+    if(flag_strong0 && flag_strong1){ /* strong filtering */
+        for(i = 0; i < 4; i++, src += stride){
+            int sflag, p0, q0, p1, q1;
+            int t = src[0*step] - src[-1*step];
+
+            if(!t) continue;
+            sflag = (alpha * FFABS(t)) >> 7;
+            if(sflag > 1) continue;
+
+            p0 = (25*src[-3*step] + 26*src[-2*step]
+                + 26*src[-1*step]
+                + 26*src[ 0*step] + 25*src[ 1*step] + rv40_dither_l[dmode + i]) >> 7;
+            q0 = (25*src[-2*step] + 26*src[-1*step]
+                + 26*src[ 0*step]
+                + 26*src[ 1*step] + 25*src[ 2*step] + rv40_dither_r[dmode + i]) >> 7;
+            if(sflag){
+                p0 = av_clip(p0, src[-1*step] - lims, src[-1*step] + lims);
+                q0 = av_clip(q0, src[ 0*step] - lims, src[ 0*step] + lims);
+            }
+            p1 = (25*src[-4*step] + 26*src[-3*step]
+                + 26*src[-2*step]
+                + 26*p0           + 25*src[ 0*step] + rv40_dither_l[dmode + i]) >> 7;
+            q1 = (25*src[-1*step] + 26*q0
+                + 26*src[ 1*step]
+                + 26*src[ 2*step] + 25*src[ 3*step] + rv40_dither_r[dmode + i]) >> 7;
+            if(sflag){
+                p1 = av_clip(p1, src[-2*step] - lims, src[-2*step] + lims);
+                q1 = av_clip(q1, src[ 1*step] - lims, src[ 1*step] + lims);
+            }
+            src[-2*step] = p1;
+            src[-1*step] = p0;
+            src[ 0*step] = q0;
+            src[ 1*step] = q1;
+            if(!chroma){
+                src[-3*step] = (25*src[-1*step] + 26*src[-2*step] + 51*src[-3*step] + 26*src[-4*step] + 64) >> 7;
+                src[ 2*step] = (25*src[ 0*step] + 26*src[ 1*step] + 51*src[ 2*step] + 26*src[ 3*step] + 64) >> 7;
+            }
+        }
+    }else if(filter_p1 && filter_q1){
+        for(i = 0; i < 4; i++, src += stride)
+            rv40_weak_loop_filter(src, step, 1, 1, alpha, beta, lims, lim_q1, lim_p1,
+                                  diff_p1p0[i], diff_q1q0[i], diff_p1p2[i], diff_q1q2[i]);
+    }else{
+        for(i = 0; i < 4; i++, src += stride)
+            rv40_weak_loop_filter(src, step, filter_p1, filter_q1,
+                                  alpha, beta, lims>>1, lim_q1>>1, lim_p1>>1,
+                                  diff_p1p0[i], diff_q1q0[i], diff_p1p2[i], diff_q1q2[i]);
+    }
+}
+
+static void rv40_v_loop_filter(uint8_t *src, int stride, int dmode,
+                               int lim_q1, int lim_p1,
+                               int alpha, int beta, int beta2, int chroma, int edge){
+    rv40_adaptive_loop_filter(src, 1, stride, dmode, lim_q1, lim_p1,
+                              alpha, beta, beta2, chroma, edge);
+}
+static void rv40_h_loop_filter(uint8_t *src, int stride, int dmode,
+                               int lim_q1, int lim_p1,
+                               int alpha, int beta, int beta2, int chroma, int edge){
+    rv40_adaptive_loop_filter(src, stride, 1, dmode, lim_q1, lim_p1,
+                              alpha, beta, beta2, chroma, edge);
+}
+
 /**
  * Initialize decoder.
  */