drivers-microphone

Introduction

This package is responsible for receiving the native audio input and parsing it to send it to the audio package for subsequent processing.

Directory Structure

shell

modules/drivers/microphone/
├── BUILD
├── conf
├── cyberfile.xml
├── dag
├── drivers-microphone.BUILD
├── launch
├── microphone_component.cc
├── microphone_component.h
├── proto
├── README.md
├── respeaker.cc
└── respeaker.h

Modules

MicrophoneComponent

apollo::drivers::microphone::MicrophoneComponent

Input

Name	Type	Description
stream	-	-

Output

Name	Type	Description
`msg`	`apollo::drivers::microphone::config::AudioDate`	Raw microphone data

configs

file path	type / struct	Description
`modules/drivers/microphone/respeaker.pb.txt`	`apollo::drivers::microphone::config::MicrophoneConfig`	microphone config

Microphone Configuration

microphone_model: currently only support RESPEAKER.
chunk: number of frames per buffer from hardware to memory each time.
record_seconds: number of seconds each time.
channel_type
- May be ASR (Audio Speech Recognition), RAW (Raw Audio Data) or Playback.
sample_rate
- Number of frames that are recorded per second.
sample_width
- Number of bytes per sample (1, 2, 3, or 4).

For example, if there are 6 channels with 16000 Hz rate and 2 bytes width, then 4 second recording is

Number of frames: 16000
Number of "samples": 16000 * 6
- I use the term "samples" here just to make it easy for understanding, which is seldom used in this context.
Total size: 6 × 16,000 x 4 × 2 = 768,000 bytes.

You might see other metrics elsewhere as follows:

BIT DEPTH same to sample_width except that the unit is bit.
BIT RATE number of bits encoded per second (kbps or k) -- for compressed format like mp3.

How to Launch

bash

cyber_launch start modules/drivers/microphone/launch/microphone.launch