Replace ALSA plugin layer resampling with libspeexdsp for improved audio
quality and reliability. This implementation uses direct hardware access
(hw:) instead of ALSA plugins (plughw:) and handles sample rate conversion
with SpeexDSP's high-quality sinc-based resampler.
Key changes:
- Add libspeexdsp 1.2.1 with ARM NEON optimizations to build dependencies
- Switch from plughw: to hw: device access for lower latency
- Implement conditional resampling (only when hardware rate ≠ 48kHz)
- Use SPEEX_RESAMPLER_QUALITY_DESKTOP for high-quality interpolation
- Add automatic audio dependency building in dev_deploy.sh
Quality improvements:
- Fix race condition in resampler cleanup with mutex protection
- Fix memory leak on resampler re-initialization
- Add buffer overflow validation (3840 frame limit for 192kHz)
- Improve error logging for resampling, encoding, and ALSA configuration
- Simplify code structure while maintaining all functionality
Technical details:
- Hardware negotiates actual sample rate (e.g., HDMI may vary)
- SpeexDSP converts hardware rate → 48kHz for Opus encoding
- USB Audio Gadget hardcoded to 48kHz (no resampling overhead)
- Static buffer allocation for zero allocation in hot path
- WebRTC requires 48kHz RTP clock rate per RFC 7587
Integrated latest dev branch changes including:
- Native process refactoring with gRPC architecture
- OTA update system refactor with new component-based updates
- Updated build system and dependencies
- UI improvements and bug fixes
Post-merge fixes applied:
- Remove duplicate OTA RPC function declarations (now in ota.go)
- Fix GetDefaultEDID reference to use native.DefaultEDID constant
- Fix IsUpdatePending to use otaState.IsUpdatePending() method
- Add missing OTA RPC handler registrations for new update system
All audio functionality from feat/audio-support preserved.
All dev branch functionality preserved.
Included the installation script for audio dependencies in the Docker build context preparation. This ensures that the necessary audio components are available during the build process.
Alex P
Aveline
Adam Shiervani