This document provides an overview of audio playback on Firefox OS (FXOS) and Android. It discusses the data flow through various components like Gecko, Gonk, MDSM, AudioSink and AudioStream on FXOS. For Android, it describes the audio output devices, profiles and playback flow through components like AudioTrack, AudioSystem, AudioPolicy Service, AudioFlinger and AudioHardware. The document also outlines the audio playback architecture on GONK and common Linux platforms.

1. Text
FxOS Audio Playback 101
Alastor Wu
2015/06/12

2. OUTLINE
2
Data flow
!
Outputs selection

3. GECKO
3
mVideoQueue
MDSM
mAudioQueue
AudioSink AudioStream
AudioLoop()
mAudioSink mAudioStream
Write()
mBuffer
AUDIO PLAYBACK OVERVIEW

4. GONK
4
AudioTrack
Audio
Buffer
MediaServer
AudioFlinger
AudioPolicy
Service
HAL
Audio
Module
AudioPolicy
Module
Linux
Kernel
ALSA/OSS
Custom Driver
AUDIO PLAYBACK OVERVIEW

5. FXOS
5
AUDIO PLAYBACK OVERVIEW
Gecko
Gonk
MDSM AudioSink AudioStream Lib Cubeb
AudioTrack AudioSystemNative Framework
AudioFlinger
AudioPolicy
Service
Media Server
AudioHardware AudioPolicyManagerHAL
Linux Kernel
OpenSL NDK

6. ANDROID
6
AUDIO OUTPUT DEVICES
StreamTypes Strategies Devices
Audio
Channel
Types
Output
device
Earpiece
Speaker
Wired headset/phone
Bluetooth SCO headset/carkit
Bluetooth A2DP headphone/speaker
…
Media
Phone
Sonification
Sonification respectful
DTMF
Enforce audible
Voice call
System
Ring
Music
Alarm
Notification
BT SCO
Enforce audible
DTMF
TTS
FM

7. ANDROID
7
AUDIO OUTPUT PROFILES
Inputs
Outputs
IOProfiles
IOProfiles
Sample rates
Channel masks
Formats
Devices
Modules
primary/a2dp/usb
khz
mono/stereo
mp3/aac/…
speaker/headset…

8. ANDROID
8
AUDIO PLAYBACK FLOW
AudioTrack
AudioSystem
AudioPolicy
Service
GetOutput() OpenOutput()
Data flow
AudioFlinger
PlaybackThread
mTracks
Audio
Mixer
AudioHardware

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END