Insight of an Audio Driver Based on ALSA
Talkat Embedded Linux Conference @ Open Source Summit North America 2022 · on Thursday, 2022-06-23· at 17:45· Room 203/204 (Level 2), JW Marriott Austin, 110 E 2nd Street Austin, TX 78701·
summary
Explains a concrete ALSA-based mobile SoC audio stack: topology of I2S controller, mixer, codec and how the regmap over I2C controls codec registers. Describes clocking rules (LR clock = sample rate), separate PCM device per DAI, and uses three DMA channels (primary, receive, secondary). Shows ALSA call sequence (PCM open → hw_params → PCM prepare → trigger) and a working Android voice-call path that switches audio from AP-playback to modem-to-codec capture.
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chapters (19)
- 0:00Basics of Audio
- 1:13Audio Block
- 2:1012S Data Formats
- 3:24CLOCK
- 5:3612C Interface for codec
- 6:1012C Layers
- 7:00S/W architecture
- 9:35Data Flow in Audio Sub-System
- 10:45Control Flow in Audio Driver
- 11:28S/W Implementation view of Audio Driver
- 12:59Sequence Diagram-Playback/Capture
- 16:12Sequence Diagrams - Mixer OPs
- 17:20Block Diagram of Mixer
- 18:37Controls in Mixer
- 19:10Kcontrol Flow
- 19:55DAPM controls
- 21:24Use case Example
- 21:36Android Audio System
- 23:13Voice Call Path
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