Audio is captured in PCM format (Pulse Code Modulation, the same as the *.wav files) and sent to your peer's output either unchanged or compressed with Opus codec at your choice. Opus is a new audio codec that has proven to be by far the best compression codec for Voip, and is standardized by the Internet Engineering Task Force (IETF) as RFC 6716 which incorporated technology from Skype's SILK codec and Xiph.Org's CELT codec. *** Android users *** in order to work on Android devices this settings are required: Audio input: device: voicerecognition pull: off Audio output: pull: on

• Input device: if more than one input device is present, select one from the top combo, or leave the default.
  Android users should select the "voicerecognition" device.
• Codec: possible values are
  • audio/pcm
  • voice/opus
  Strongly suggested value: voice/opus, it use opus compression thus bit/rates are dropped down to no more than 10%; for example at 8000Hz and 16 bits the PCM bit rate is dropped from 16 Kb/s to about 1 Kb/s;
• Bits: sampling size (values prefixed with a '+' sign are not supported by your sound card, but usually you can force them);
• Hz: sampling rate (values prefixed with a '+' sign are not supported by your sound card, but usually you can force them);
  
  For opus compression to work properly Hz must be one of:
  8000, 12000, 16000, 24000 or 48000;
• P2T: push to talk, if it is selected to activate the mic you can press the button or the <control> key on your keyboard;
• Tmr: push timer interval (not to be confused with push to talk!), when Pull is not selected this is the time lapse in milliseconds at which audio samples are read from the sound card and sent to the network stream;
  special values
  • -1: preferred value, based on device period-size (value is printed to log);
  • 0: as fast as possible, super CPU intensive;
• Pull: Let device decide when to send data to network stream (no push timer), this is less CPU intensive and the preferred default for input (except for Android!).

The level-meter indicates the audio input volume. Color indicates:

•      yellow: compression off;
•      green: compression on;
•      red: opus is selected with wrong sampling rate.

• Output device: if more than one input device is present, select one from the top combo, or leave the default.
  
• Codec: possible values are
  • audio/pcm
  • voice/opus
  Strongly suggested value: voice/opus, it use opus compression thus bit/rates are dropped down to no more than 10%; for example at 8000Hz and 16 bits the PCM bit rate is dropped from 16 Kb/s to about 1 Kb/s;
• Bits: sampling size (values prefixed with a '+' sign are not supported by your sound card, but usually you can force them);
• Hz: sampling rate (values prefixed with a '+' sign are not supported by your sound card, but usually you can force them);
  
  For opus compression to work properly Hz must be one of:
  8000, 12000, 16000, 24000 or 48000;
• Tmr: push timer interval (not to be confused with push to talk!), when Pull is not selected this is the time lapse in milliseconds at which audio samples are read from the network stream and sent to the sound card;
  special values
  • -1: preferred value, based on device period-size (value is printed to log);
  • 0: as fast as possible, super CPU intensive;
• Pull: Let device decide when read data from network stream (no push timer), this is less CPU intensive but more prone to buffer underrun (however is mandatory on Android!).

The level-meter indicates the audio output volume. Color indicates:

•      yellow: compression off;
•      green: compression on;
•      red: opus is selected with wrong sampling rate.

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