dca: remove embedded downmix coefficient extraction.

It was based on an old, seemingly incorrect specification, so default
coefficients were always used anyway.

Signed-off-by: Anton Khirnov <anton@khirnov.net>

2 files changed, 17 insertions, 44 deletions

diff --git a/libavcodec/dcadata.h b/libavcodec/dcadata.h
index e8f07e8beb..c4841fbac8 100644
--- a/libavcodec/dcadata.h
+++ b/libavcodec/dcadata.h
@@ -7505,23 +7505,6 @@ DECLARE_ALIGNED(16, static const float, lfe_fir_128)[] =
     0.01724460535, 0.47964480519, 0.48503074050, 0.01805862412,
 };
 
-/* 10^-(dB/20), with dB being a list of dB values ranging from 0 to -72 */
-/* do a 20*log10(dca_downmix_coeffs) to reconvert the values */
-
-static const float dca_downmix_coeffs[65] = {
-  1.000000000000000, 0.988553094656939, 0.971627951577106, 0.944060876285923, 0.917275935389780, 0.891250938133746,
-  0.865964323360065, 0.841395141645195, 0.817523037943650, 0.794328234724281, 0.771791515585012, 0.749894209332456,
-  0.728618174513228, 0.707945784384138, 0.687859912308808, 0.668343917568615, 0.649381631576211, 0.630957344480193,
-  0.613055792149821, 0.595662143529010, 0.578761988349121, 0.562341325190349, 0.546386549881854, 0.530884444230988,
-  0.515822165072306, 0.501187233627272, 0.446683592150963, 0.398107170553497, 0.354813389233575, 0.316227766016838,
-  0.281838293126445, 0.251188643150958, 0.223872113856834, 0.199526231496888, 0.177827941003892, 0.158489319246111,
-  0.141253754462275, 0.125892541179417, 0.112201845430196, 0.100000000000000, 0.089125093813374, 0.079432823472428,
-  0.070794578438414, 0.063095734448019, 0.053088444423099, 0.044668359215096, 0.037583740428844, 0.031622776601684,
-  0.026607250597988, 0.022387211385683, 0.018836490894898, 0.015848931924611, 0.013335214321633, 0.011220184543020,
-  0.009440608762859, 0.007943282347243, 0.005623413251903, 0.003981071705535, 0.002818382931264, 0.001995262314969,
-  0.001412537544623, 0.001000000000000, 0.000501187233627, 0.000251188643151, 0.000000000000000,
-};
-
 static const float dca_default_coeffs[10][5][2] = {
     { { 0.707946, 0.707946 },                                                                                                 }, // A
     { { 1.000000, 0.000000 }, { 0.000000, 1.000000 },                                                                         }, // A + B (dual mono)
diff --git a/libavcodec/dcadec.c b/libavcodec/dcadec.c
index 33a2ac6e9a..eb229ce98e 100644
--- a/libavcodec/dcadec.c
+++ b/libavcodec/dcadec.c
@@ -295,7 +295,6 @@ typedef struct {
     int bit_rate;               ///< transmission bit rate
     int bit_rate_index;         ///< transmission bit rate index
 
-    int downmix;                ///< embedded downmix enabled
     int dynrange;               ///< embedded dynamic range flag
     int timestamp;              ///< embedded time stamp flag
     int aux_data;               ///< auxiliary data flag
@@ -569,7 +568,7 @@ static int dca_parse_frame_header(DCAContext *s)
     if (!s->bit_rate)
         return AVERROR_INVALIDDATA;
 
-    s->downmix           = get_bits(&s->gb, 1);
+    skip_bits1(&s->gb); // always 0 (reserved, cf. ETSI TS 102 114 V1.4.1)
     s->dynrange          = get_bits(&s->gb, 1);
     s->timestamp         = get_bits(&s->gb, 1);
     s->aux_data          = get_bits(&s->gb, 1);
@@ -615,7 +614,6 @@ static int dca_parse_frame_header(DCAContext *s)
            s->sample_rate);
     av_log(s->avctx, AV_LOG_DEBUG, "bit rate: %i bits/s\n",
            s->bit_rate);
-    av_log(s->avctx, AV_LOG_DEBUG, "downmix: %i\n", s->downmix);
     av_log(s->avctx, AV_LOG_DEBUG, "dynrange: %i\n", s->dynrange);
     av_log(s->avctx, AV_LOG_DEBUG, "timestamp: %i\n", s->timestamp);
     av_log(s->avctx, AV_LOG_DEBUG, "aux_data: %i\n", s->aux_data);
@@ -800,28 +798,20 @@ static int dca_subframe_header(DCAContext *s, int base_channel, int block_index)
 
     /* Stereo downmix coefficients */
     if (!base_channel && s->prim_channels > 2) {
-        if (s->downmix) {
-            for (j = base_channel; j < s->prim_channels; j++) {
-                s->downmix_coef[j][0] = dca_downmix_coeffs[get_bits(&s->gb, 7)];
-                s->downmix_coef[j][1] = dca_downmix_coeffs[get_bits(&s->gb, 7)];
-            }
-        } else {
-            int am = s->amode & DCA_CHANNEL_MASK;
-            if (am >= FF_ARRAY_ELEMS(dca_default_coeffs)) {
-                av_log(s->avctx, AV_LOG_ERROR,
-                       "Invalid channel mode %d\n", am);
-                return AVERROR_INVALIDDATA;
-            }
-            if (s->prim_channels > FF_ARRAY_ELEMS(dca_default_coeffs[0])) {
-                avpriv_request_sample(s->avctx, "Downmixing %d channels",
-                                      s->prim_channels);
-                return AVERROR_PATCHWELCOME;
-            }
-
-            for (j = base_channel; j < s->prim_channels; j++) {
-                s->downmix_coef[j][0] = dca_default_coeffs[am][j][0];
-                s->downmix_coef[j][1] = dca_default_coeffs[am][j][1];
-            }
+        int am = s->amode & DCA_CHANNEL_MASK;
+        if (am >= FF_ARRAY_ELEMS(dca_default_coeffs)) {
+            av_log(s->avctx, AV_LOG_ERROR,
+                   "Invalid channel mode %d\n", am);
+            return AVERROR_INVALIDDATA;
+        }
+        if (s->prim_channels > FF_ARRAY_ELEMS(dca_default_coeffs[0])) {
+            avpriv_request_sample(s->avctx, "Downmixing %d channels",
+                                  s->prim_channels);
+            return AVERROR_PATCHWELCOME;
+        }
+        for (j = base_channel; j < s->prim_channels; j++) {
+            s->downmix_coef[j][0] = dca_default_coeffs[am][j][0];
+            s->downmix_coef[j][1] = dca_default_coeffs[am][j][1];
         }
     }
 
@@ -919,7 +909,7 @@ static int dca_subframe_header(DCAContext *s, int base_channel, int block_index)
             av_log(s->avctx, AV_LOG_DEBUG, "\n");
         }
     }
-    if (!base_channel && s->prim_channels > 2 && s->downmix) {
+    if (!base_channel && s->prim_channels > 2) {
         av_log(s->avctx, AV_LOG_DEBUG, "Downmix coeffs:\n");
         for (j = 0; j < s->prim_channels; j++) {
             av_log(s->avctx, AV_LOG_DEBUG, "Channel 0, %d = %f\n", j,
@@ -1319,7 +1309,7 @@ static int dca_subframe_footer(DCAContext *s, int base_channel)
         for (i = 0; i < aux_data_count; i++)
             get_bits(&s->gb, 8);
 
-        if (s->crc_present && (s->downmix || s->dynrange))
+        if (s->crc_present && s->dynrange)
             get_bits(&s->gb, 16);
     }