Audio

le_audio functions are constrained by the following platform limitations.

DTMF, playback and recording:

  • DTMF decoding works only on MdmVoice Rx stream. DTMF's reception handler must be installed before call initiation.
  • File Playback/Recording: WAVE, AMR Narrowband and AMR Wideband formats are supported.
  • Only one Recording/sample extraction can be activated simultaneously.

Possible audio connections:

Input stream \ Output stream Spkr USB Tx PCM Tx I2S Tx MdmVoice Tx Recorder
Mic X X
USB Rx X X
PCM Rx X X
I2S Rx X X
MdmVoice Rx X X X X X
Player X X X X X

Player = file playback and samples insertion
Recorder = file recording and samples extraction

Note
The Mic input and Spkr output are not available on AR759x platform.
Please refer to the Product Technical Specification document of your platform for further details.

Only 1 point to 1 point connection is possible except for Player and Recorder.
Player and Recorder can be added to any active 1 point to 1 point connections, or tied to 1 single stream.

Available functions for the different audio streams:

Function \ Stream I2S Tx I2S Rx PCM Tx PCM Rx USB Tx USB Rx Spkr Mic MdmVoice Tx MdmVoice Rx Player Recorder
Gain (Set / Get) X X X X
Mute / Unmute X X X X
NS X
EC X
IIR X X
FIR X X
AGC X X X X X X

NS = Noise Suppressor
EC = Echo Canceller
IIR = Infinite Impulse Response filter
FIR = Finite Impulse Response filter
AGC = Automatic Gain Control

Gains value's:

Mic:

  • range: 0x0000 -- 0xFFFF;
  • value (in dB) = 20*Log(<value>/0x0100)

MdmVoiceRx:

  • range: 0 - 8 (integer);
  • the value is not in dB, '0' means lowest volume value (not muted) and '8' means the highest volume value.

MdmVoiceTx:

  • range: 0x0000 -- 0xFFFF;
  • value (in dB) = 20*Log(<value>/0x2000)

Player:

  • range: 0x0000 -- 0xFFFF;
  • value (in dB) = 20*Log(<value>/0x2000)
Note
AR specific gains can use the le_audio_SetPlatformSpecificGain() function with "D_AFE_GAIN_RX" and "D_AFE_GAIN_TX" parameters.

"D_AFE_GAIN_RX":

  • range: 0x0000 -- 0xFFFF;
  • value (in dB) = 20*Log(<value>/0x2000)

"D_AFE_GAIN_TX":

  • range: 0x0000 -- 0xFFFF;
  • value (in dB) = 20*Log(<value>/0x2000)

The following diagram shows where the functions are applied in a voice call audio path (applicable for AR755x, AR8652, WP8548):

AR755x_Ext_AudioBlockDiagram_Legato.jpg