swresample: Allow reinitialization without ever setting channel counts

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

libswresample/options.c

@@ -35,12 +35,12 @@
 #define PARAM AV_OPT_FLAG_AUDIO_PARAM
 
 static const AVOption options[]={
-{"ich"                  , "set input channel count"     , OFFSET( in.ch_count   ), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , SWR_CH_MAX, PARAM},
-{"in_channel_count"     , "set input channel count"     , OFFSET( in.ch_count   ), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , SWR_CH_MAX, PARAM},
-{"och"                  , "set output channel count"    , OFFSET(out.ch_count   ), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , SWR_CH_MAX, PARAM},
-{"out_channel_count"    , "set output channel count"    , OFFSET(out.ch_count   ), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , SWR_CH_MAX, PARAM},
-{"uch"                  , "set used channel count"      , OFFSET(used_ch_count  ), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , SWR_CH_MAX, PARAM},
-{"used_channel_count"   , "set used channel count"      , OFFSET(used_ch_count  ), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , SWR_CH_MAX, PARAM},
+{"ich"                  , "set input channel count"     , OFFSET(user_in_ch_count  ), AV_OPT_TYPE_INT, {.i64=0                    }, 0      , SWR_CH_MAX, PARAM},
+{"in_channel_count"     , "set input channel count"     , OFFSET(user_in_ch_count  ), AV_OPT_TYPE_INT, {.i64=0                    }, 0      , SWR_CH_MAX, PARAM},
+{"och"                  , "set output channel count"    , OFFSET(user_out_ch_count ), AV_OPT_TYPE_INT, {.i64=0                    }, 0      , SWR_CH_MAX, PARAM},
+{"out_channel_count"    , "set output channel count"    , OFFSET(user_out_ch_count ), AV_OPT_TYPE_INT, {.i64=0                    }, 0      , SWR_CH_MAX, PARAM},
+{"uch"                  , "set used channel count"      , OFFSET(user_used_ch_count), AV_OPT_TYPE_INT, {.i64=0                    }, 0      , SWR_CH_MAX, PARAM},
+{"used_channel_count"   , "set used channel count"      , OFFSET(user_used_ch_count), AV_OPT_TYPE_INT, {.i64=0                    }, 0      , SWR_CH_MAX, PARAM},
 {"isr"                  , "set input sample rate"       , OFFSET( in_sample_rate), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , INT_MAX   , PARAM},
 {"in_sample_rate"       , "set input sample rate"       , OFFSET( in_sample_rate), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , INT_MAX   , PARAM},
 {"osr"                  , "set output sample rate"      , OFFSET(out_sample_rate), AV_OPT_TYPE_INT  , {.i64=0                     }, 0      , INT_MAX   , PARAM},

libswresample/swresample.c

@@ -164,6 +164,10 @@ av_cold int swr_init(struct SwrContext *s){
         return AVERROR(EINVAL);
     }
 
+    s->out.ch_count  = s-> user_out_ch_count;
+    s-> in.ch_count  = s->  user_in_ch_count;
+    s->used_ch_count = s->user_used_ch_count;
+
     if(av_get_channel_layout_nb_channels(s-> in_ch_layout) > SWR_CH_MAX) {
         av_log(s, AV_LOG_WARNING, "Input channel layout 0x%"PRIx64" is invalid or unsupported.\n", s-> in_ch_layout);
         s->in_ch_layout = 0;

libswresample/swresample_internal.h

@@ -112,6 +112,10 @@ struct SwrContext {
     int used_ch_count;                              ///< number of used input channels (mapped channel count if channel_map, otherwise in.ch_count)
     int engine;
 
+    int user_in_ch_count;                           ///< User set input channel count
+    int user_out_ch_count;                          ///< User set output channel count
+    int user_used_ch_count;                         ///< User set used channel count
+
     struct DitherContext dither;
 
     int filter_size;                                /**< length of each FIR filter in the resampling filterbank relative to the cutoff frequency */