dca: Convert dca_dmixtable to integers

Also include zero in the table, eliminating a special case in the
decoder.

Signed-off-by: Niels Möller <nisse@southpole.se>
Signed-off-by: Anton Khirnov <anton@khirnov.net>

1 files changed, 10 insertions, 9 deletions

diff --git a/libavcodec/dcadec.c b/libavcodec/dcadec.c
index c8877d6d1f..0727857bb6 100644
--- a/libavcodec/dcadec.c
+++ b/libavcodec/dcadec.c
@@ -1695,6 +1695,13 @@ static void dca_exss_parse_header(DCAContext *s)
      * from the asset header */
 }
 
+static float dca_dmix_code(unsigned code)
+{
+    int sign = (code >> 8) - 1;
+    code &= 0xff;
+    return ldexpf((dca_dmixtable[code] ^ sign) - sign, -15);
+}
+
 /**
  * Main frame decoding function
  * FIXME add arguments
@@ -1902,16 +1909,10 @@ FF_ENABLE_DEPRECATION_WARNINGS
              */
             if (s->core_downmix && (s->core_downmix_amode == DCA_STEREO ||
                                     s->core_downmix_amode == DCA_STEREO_TOTAL)) {
-                int sign, code;
                 for (i = 0; i < num_core_channels + !!s->lfe; i++) {
-                    sign = s->core_downmix_codes[i][0] & 0x100 ? 1 : -1;
-                    code = s->core_downmix_codes[i][0] & 0x0FF;
-                    s->downmix_coef[i][0] = (!code ? 0.0f :
-                                             sign * dca_dmixtable[code - 1]);
-                    sign = s->core_downmix_codes[i][1] & 0x100 ? 1 : -1;
-                    code = s->core_downmix_codes[i][1] & 0x0FF;
-                    s->downmix_coef[i][1] = (!code ? 0.0f :
-                                             sign * dca_dmixtable[code - 1]);
+                    /* Range checked earlier */
+                    s->downmix_coef[i][0] = dca_dmix_code(s->core_downmix_codes[i][0]);
+                    s->downmix_coef[i][1] = dca_dmix_code(s->core_downmix_codes[i][1]);
                 }
                 s->output = s->core_downmix_amode;
             } else {