Audio
Audio functions are constrained by the following platform limitations for AR755x, AR8652, and WP8548.
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
- 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
The following diagram shows where the functions are applied in a voice call audio path:
Gains value's for AR7x series (also applicable for AR8652):
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)
Other audio features and constraints:
- 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.
- Samples insertion/extraction: PCM samples using configuration of channel number, sampling rate and sampling resolution.
- Several file playbacks can be activated simultaneously but not several file recordings. Playback and recording can’t be performed simultaneously. This also applies to samples insertion/extraction.
Copyright (C) Sierra Wireless Inc. Use of this work is subject to license.