swr: add lfe_mix_level

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

libswresample/rematrix.c

@@ -216,6 +216,17 @@ static int auto_matrix(SwrContext *s)
         }else
             av_assert0(0);
     }
+    /* mix LFE into front left/right or center */
+    if (unaccounted & AV_CH_LOW_FREQUENCY) {
+        if (s->out_ch_layout & AV_CH_FRONT_CENTER) {
+            matrix[FRONT_CENTER][LOW_FREQUENCY] += s->lfe_mix_level;
+        } else if (s->out_ch_layout & AV_CH_FRONT_LEFT) {
+            matrix[FRONT_LEFT ][LOW_FREQUENCY] += s->lfe_mix_level * M_SQRT1_2;
+            matrix[FRONT_RIGHT][LOW_FREQUENCY] += s->lfe_mix_level * M_SQRT1_2;
+        } else
+            av_assert0(0);
+    }
+
     for(out_i=i=0; i<64; i++){
         double sum=0;
         int in_i=0;

libswresample/swresample.c

@@ -62,6 +62,7 @@ static const AVOption options[]={
 {"center_mix_level"     ,    "Center Mix Level"         , OFFSET(clev           ), AV_OPT_TYPE_FLOAT, {.dbl=C_30DB                }, -32    , 32        , PARAM},
 {"slev"                 , "Sourround Mix Level"         , OFFSET(slev           ), AV_OPT_TYPE_FLOAT, {.dbl=C_30DB                }, -32    , 32        , PARAM},
 {"surround_mix_level"   , "Sourround Mix Level"         , OFFSET(slev           ), AV_OPT_TYPE_FLOAT, {.dbl=C_30DB                }, -32    , 32        , PARAM},
+{"lfe_mix_level"        , "LFE Mix Level"               , OFFSET(lfe_mix_level  ), AV_OPT_TYPE_FLOAT, {.dbl=0                     }, -32    , 32        , PARAM},
 {"rmvol"                , "Rematrix Volume"             , OFFSET(rematrix_volume), AV_OPT_TYPE_FLOAT, {.dbl=1.0                   }, -1000  , 1000      , PARAM},
 {"rematrix_volume"      , "Rematrix Volume"             , OFFSET(rematrix_volume), AV_OPT_TYPE_FLOAT, {.dbl=1.0                   }, -1000  , 1000      , PARAM},
 {"flags"                , NULL                          , OFFSET(flags          ), AV_OPT_TYPE_FLAGS, {.dbl=0                     }, 0      , UINT_MAX  , PARAM, "flags"},

libswresample/swresample_internal.h

@@ -50,6 +50,7 @@ struct SwrContext {
     int flags;                                      ///< miscellaneous flags such as SWR_FLAG_RESAMPLE
     float slev;                                     ///< surround mixing level
     float clev;                                     ///< center mixing level
+    float lfe_mix_level;                            ///< LFE mixing level
     float rematrix_volume;                          ///< rematrixing volume coefficient
     const int *channel_map;                         ///< channel index (or -1 if muted channel) map
     int used_ch_count;                              ///< number of used input channels (mapped channel count if channel_map, otherwise in.ch_count)