Improved AC3 decoder level support (heavy drc, dialnorm)

Added support for AC3 heavy dynamic range compression used
to restrict the output range and added a setting to specify
the output target level and use the dialog normalization
field to apply it in the digital domain.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 65 insertions, 34 deletions

diff --git a/libavcodec/ac3dec_fixed.c b/libavcodec/ac3dec_fixed.c
index c6cbeb9b28..f36e7b0849 100644
--- a/libavcodec/ac3dec_fixed.c
+++ b/libavcodec/ac3dec_fixed.c
@@ -81,40 +81,69 @@ static void scale_coefs (
     int temp, temp1, temp2, temp3, temp4, temp5, temp6, temp7;
 
     mul = (dynrng & 0x1f) + 0x20;
-    shift = 4 - ((dynrng << 24) >> 29);
-    round = 1 << (shift-1);
-    for (i=0; i<len; i+=8) {
-
-        temp = src[i] * mul;
-        temp1 = src[i+1] * mul;
-        temp = temp + round;
-        temp2 = src[i+2] * mul;
-
-        temp1 = temp1 + round;
-        dst[i] = temp >> shift;
-        temp3 = src[i+3] * mul;
-        temp2 = temp2 + round;
-
-        dst[i+1] = temp1 >> shift;
-        temp4 = src[i + 4] * mul;
-        temp3 = temp3 + round;
-        dst[i+2] = temp2 >> shift;
-
-        temp5 = src[i+5] * mul;
-        temp4 = temp4 + round;
-        dst[i+3] = temp3 >> shift;
-        temp6 = src[i+6] * mul;
-
-        dst[i+4] = temp4 >> shift;
-        temp5 = temp5 + round;
-        temp7 = src[i+7] * mul;
-        temp6 = temp6 + round;
-
-        dst[i+5] = temp5 >> shift;
-        temp7 = temp7 + round;
-        dst[i+6] = temp6 >> shift;
-        dst[i+7] = temp7 >> shift;
-
+    shift = 4 - ((dynrng << 23) >> 28);
+    if (shift > 0 ) {
+      round = 1 << (shift-1);
+      for (i=0; i<len; i+=8) {
+
+          temp = src[i] * mul;
+          temp1 = src[i+1] * mul;
+          temp = temp + round;
+          temp2 = src[i+2] * mul;
+
+          temp1 = temp1 + round;
+          dst[i] = temp >> shift;
+          temp3 = src[i+3] * mul;
+          temp2 = temp2 + round;
+
+          dst[i+1] = temp1 >> shift;
+          temp4 = src[i + 4] * mul;
+          temp3 = temp3 + round;
+          dst[i+2] = temp2 >> shift;
+
+          temp5 = src[i+5] * mul;
+          temp4 = temp4 + round;
+          dst[i+3] = temp3 >> shift;
+          temp6 = src[i+6] * mul;
+
+          dst[i+4] = temp4 >> shift;
+          temp5 = temp5 + round;
+          temp7 = src[i+7] * mul;
+          temp6 = temp6 + round;
+
+          dst[i+5] = temp5 >> shift;
+          temp7 = temp7 + round;
+          dst[i+6] = temp6 >> shift;
+          dst[i+7] = temp7 >> shift;
+
+      }
+    } else {
+      shift = -shift;
+      for (i=0; i<len; i+=8) {
+
+          temp = src[i] * mul;
+          temp1 = src[i+1] * mul;
+          temp2 = src[i+2] * mul;
+
+          dst[i] = temp << shift;
+          temp3 = src[i+3] * mul;
+
+          dst[i+1] = temp1 << shift;
+          temp4 = src[i + 4] * mul;
+          dst[i+2] = temp2 << shift;
+
+          temp5 = src[i+5] * mul;
+          dst[i+3] = temp3 << shift;
+          temp6 = src[i+6] * mul;
+
+          dst[i+4] = temp4 << shift;
+          temp7 = src[i+7] * mul;
+
+          dst[i+5] = temp5 << shift;
+          dst[i+6] = temp6 << shift;
+          dst[i+7] = temp7 << shift;
+
+      }
     }
 }
 
@@ -150,6 +179,8 @@ static void ac3_downmix_c_fixed16(int16_t **samples, int16_t (*matrix)[2],
 #include "ac3dec.c"
 
 static const AVOption options[] = {
+    { "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale), AV_OPT_TYPE_FLOAT, {.dbl = 1.0}, 0.0, 6.0, PAR },
+    { "heavy_compr", "heavy dynamic range compression enabled", OFFSET(heavy_compression), AV_OPT_TYPE_INT, {.i64 = 0 }, 0, 1, PAR },
     { NULL},
 };