Comment 1 for bug 1538327

p.s. the below diff seems to be sufficient for Ubuntu 14.04 (trusty) support:

--- a/src/media-profiles.c
+++ b/src/media-profiles.c
@@ -34,6 +34,8 @@ ProfileRec DefaultProfiles[] = {
  {"voicelossless44","Lossless 44KHz", "wav", "audio/x-raw,rate=44100,chann

  {"voicelossy", "Lossy 32KHz", "spx", "audio/x-raw,rate=32000,chann
+ {"voicelossymono", "Speex Mono Lossy 16KHz", "spx", "audio/x-raw,rate=16000,
+ {"opuslossymono", "Opus Mono Lossy 16KHz", "opus", "audio/x-raw,rate=16000,
 };

 // ! audio/x-raw,rate=44100 ! vorbisenc ! queue ! mux.audio_0