diff -Naur a52dec_original/include/a52.h a52dec_patched/include/a52.h
--- a52dec_original/include/a52.h	2002-01-28 05:37:54.000000000 +0000
+++ a52dec_patched/include/a52.h	2007-04-04 19:12:57.000000000 +0100
@@ -48,6 +48,10 @@
 #define A52_LFE 16
 #define A52_ADJUST_LEVEL 32
 
+// this next constant can be ORed with A52_DOLBY to tell liba52 to use 5.0 DPLII matrix encoding,
+// rather than just 4.0 Dolby Surround matrix encoding
+#define A52_USE_DPLII 64
+
 a52_state_t * a52_init (uint32_t mm_accel);
 sample_t * a52_samples (a52_state_t * state);
 int a52_syncinfo (uint8_t * buf, int * flags,
diff -Naur a52dec_original/liba52/a52_internal.h a52dec_patched/liba52/a52_internal.h
--- a52dec_original/liba52/a52_internal.h	2002-07-28 02:52:06.000000000 +0100
+++ a52dec_patched/liba52/a52_internal.h	2007-04-04 19:11:43.000000000 +0100
@@ -93,6 +93,10 @@
 #define LEVEL_45DB 0.5946035575013605
 #define LEVEL_6DB 0.5
 
+// these next two constants are used for DPL matrix encoding in downmix.c
+#define LEVEL_SQRT_1_2 0.5
+#define LEVEL_SQRT_3_4 0.8660254037844386
+
 #define EXP_REUSE (0)
 #define EXP_D15   (1)
 #define EXP_D25   (2)
diff -Naur a52dec_original/liba52/downmix.c a52dec_patched/liba52/downmix.c
--- a52dec_original/liba52/downmix.c	2002-01-28 05:37:54.000000000 +0000
+++ a52dec_patched/liba52/downmix.c	2007-04-06 13:47:49.000000000 +0100
@@ -34,6 +34,7 @@
 int a52_downmix_init (int input, int flags, sample_t * level,
 		      sample_t clev, sample_t slev)
 {
+
     static uint8_t table[11][8] = {
 	{A52_CHANNEL,	A52_DOLBY,	A52_STEREO,	A52_STEREO,
 	 A52_STEREO,	A52_STEREO,	A52_STEREO,	A52_STEREO},
@@ -148,6 +149,9 @@
 	    break;
 	}
 
+	// add the DPLII flag back into the output if it was passed in
+	output = output | (flags & A52_USE_DPLII);
+
     return output;
 }
 
@@ -418,17 +422,46 @@
     }
 }
 
-static void mix32toS (sample_t * samples, sample_t bias)
+static void mix32toS (sample_t * samples, sample_t bias, int use_dpl2)
 {
-    int i;
-    sample_t common, surround;
 
-    for (i = 0; i < 256; i++) {
-	common = samples[i + 256] + bias;
-	surround = samples[i + 768] + samples[i + 1024];
-	samples[i] += common - surround;
-	samples[i + 256] = samples[i + 512] + common + surround;
-    }
+	if (use_dpl2 == 1) {
+
+		int i;
+		sample_t cc, Lt, Rt, Ls, Rs, Lss, Rss;
+	
+		for (i = 0; i < 256; i++) {
+	
+			cc = samples[i + 256] * LEVEL_3DB;
+		
+			Lt = samples[i] + cc;
+			Rt = samples[i + 512] + cc;
+		
+			Ls = samples[i + 768];
+			Rs = samples[i + 1024];
+			
+			Lss = (LEVEL_SQRT_3_4 * Ls) - (LEVEL_SQRT_1_2 * Rs);
+			Rss = -(LEVEL_SQRT_1_2 * Ls) + (LEVEL_SQRT_3_4 * Rs);
+		
+			samples[i] = Lt + Lss;
+			samples[i + 256] = Rt + Rss;
+	
+		}
+
+	} else {
+
+		int i;
+		sample_t common, surround;
+	
+		for (i = 0; i < 256; i++) {
+		common = samples[i + 256] + bias;
+		surround = samples[i + 768] + samples[i + 1024];
+		samples[i] += common - surround;
+		samples[i + 256] = samples[i + 512] + common + surround;
+		}
+
+	}
+
 }
 
 static void move2to1 (sample_t * src, sample_t * dest, sample_t bias)
@@ -533,7 +566,7 @@
 	break;
 
     case CONVERT (A52_3F2R, A52_DOLBY):
-	mix32toS (samples, bias);
+	mix32toS (samples, bias, ((output & A52_USE_DPLII) == A52_USE_DPLII));
 	break;
 
     case CONVERT (A52_3F1R, A52_3F):