--- cbp.c	2002/03/28 20:57:24	1.3
+++ cbp.c	2003/03/27 14:56:52	1.10.2.1
@@ -7,28 +7,80 @@
  * Returns a field of bits that indicates non zero ac blocks
  * for this macro block
  */
-uint32_t calc_cbp_c(const int16_t codes[6*64])
+
+/* naive C */
+uint32_t
+calc_cbp_plain(const int16_t codes[6 * 64])
 {
-	uint32_t i, j;
+	int i, j;
 	uint32_t cbp = 0;
 
-	for (i = 0; i < 6*64; i+=64)
-	{
-		for (j = 1; j < 61; j+=4)
-		{
-			if (codes[i + j    ]|codes[i + j + 1]|
-			    codes[i + j + 2]|codes[i + j + 3])
-			{
-				cbp |= 1 << (5 - i);
+	for (i = 0; i < 6; i++) {
+		for (j=1; j<64;j++) {
+			if (codes[64*i+j]) {
+            	cbp |= 1 << (5-i);
 				break;
 			}
 		}
+	}
+	return cbp;
+}
 
-		if(codes[i + j]|codes[i + j +1]|codes[i + j + 2])
-			cbp |= 1 << (5 - i);
+/* optimized C */
+uint32_t
+calc_cbp_c(const int16_t codes[6 * 64])
+{
+	unsigned int i=6;
+	uint32_t cbp = 0;
 
-	}
+/* uses fixed relation: 4*codes = 1*codes64 */
+/* if prototype is changed (e.g. from int16_t to something like int32) this routine 
+   has to be changed! */
 
-	return cbp;
+	do  {
+		uint64_t *codes64 = (uint64_t*)codes;	/* the compiler doesn't really make this */
+		uint32_t *codes32 = (uint32_t*)codes;	/* variables, just "addressing modes" */
 
+		cbp += cbp; 
+        if (codes[1] || codes32[1]) {
+			cbp++;
+		}
+        else if (codes64[1] | codes64[2] | codes64[3]) {
+			cbp++;
+		}
+        else if (codes64[4] | codes64[5] | codes64[6] | codes64[7]) {
+			cbp++;
+		}
+        else if (codes64[8] | codes64[9] | codes64[10] | codes64[11]) {
+			cbp++;
+		}
+        else if (codes64[12] | codes64[13] | codes64[14] | codes64[15]) {
+			cbp++;
+		}
+		codes += 64;
+		i--;
+    } while (i != 0);
+
+	return cbp;
 }
+
+
+
+
+/* older code maybe better on some plattforms? */
+#if 0
+	for (i = 5; i >= 0; i--) {
+		if (codes[1] | codes[2] | codes[3])
+                        cbp |= 1 << i;
+		else {
+			for (j = 4; j <= 56; j+=4) 	/* [60],[61],[62],[63] are last */
+				if (codes[j] | codes[j+1] | codes[j+2] | codes[j+3]) {
+				cbp |= 1 << i;
+				break;
+			}
+		}
+		codes += 64;
+	}
+
+	return cbp;
+#endif