[#1962] Use ALSA's plug:dmix only for playback, does not support capture

sflphone-common/src/audio/alsa/alsalayer.cpp

@@ -137,13 +137,9 @@ AlsaLayer::startStream (void)
     _debug ("AlsaLayer:: startStream");
 
     std::string pcmp = buildDeviceTopo (_audioPlugin, _indexOut, 0);
-    std::string pcmc = buildDeviceTopo (_audioPlugin, _indexIn, 0);
+    std::string pcmr = buildDeviceTopo (_audioPlugin, _indexRing, 0);
 
-    std::string pcmr;
-    if(_audioPlugin != "plug:dmix")
-        pcmr = buildDeviceTopo (_audioPlugin, _indexRing, 0);
-    else
-        pcmr = buildDeviceTopo("default", _indexRing, 0);
+    std::string pcmc = buildDeviceTopo("default", _indexIn, 0);
 
     if (!is_playback_open()) {
         open_device (pcmp, pcmc, pcmr, SFL_PCM_PLAYBACK);