fix bad handling of audio rate in audio conference when opus codec is used on android.

include/mediastreamer2/msfilter.h

@@ -431,7 +431,7 @@ MS2_PUBLIC int ms_filter_call_method_noarg(MSFilter *f, unsigned int id);
  * @param f    A MSFilter object.
  * @param id   A method ID.
  *
- * Returns: 0 if successfull, -1 otherwise.
+ * Returns: TRUE if method is implemented, FALSE otherwise.
  */
 MS2_PUBLIC bool_t ms_filter_has_method(MSFilter *f, unsigned int id);
 

src/voip/audioconference.c

@@ -103,7 +103,9 @@ static void cut_audio_stream_graph(MSAudioEndpoint *ep, bool_t is_remote){
 	ep->out_cut_point=just_before(st->ms.encoder);
 	ms_filter_unlink(ep->out_cut_point.filter,ep->out_cut_point.pin,st->ms.encoder,0);
 
-	ms_filter_call_method(st->ms.rtpsend,MS_FILTER_GET_SAMPLE_RATE,&ep->samplerate);
+	if (ms_filter_has_method(st->ms.encoder,MS_FILTER_GET_SAMPLE_RATE)){
+		ms_filter_call_method(st->ms.encoder,MS_FILTER_GET_SAMPLE_RATE,&ep->samplerate);
+	}else ms_warning("MSAudioConference: filter %s does not implement MS_FILTER_GET_SAMPLE_RATE, assuming 8khz",st->ms.encoder->desc->name);
 
 	if (is_remote){
 		ep->mixer_in.filter=ep->in_cut_point_prev.filter;