Remove all subprocess-based audio code to simplify the audio system and
reduce complexity. Audio now uses CGO in-process mode exclusively.
Changes:
- Remove subprocess mode: Deleted Supervisor, IPCSource, embed.go
- Remove audio mode selection from UI (Settings → Audio)
- Remove audio mode from backend config (AudioMode field)
- Remove JSON-RPC handlers: getAudioMode/setAudioMode
- Remove Makefile targets: build_audio_output/input/binaries
- Remove standalone C binaries: jetkvm_audio_{input,output}.c
- Remove IPC protocol implementation: ipc_protocol.{c,h}
- Remove unused IPC functions from audio_common.{c,h}
- Simplify audio.go: startAudio() instead of startAudioSubprocesses()
- Update all function calls and comments to remove subprocess references
- Add constants to cgo_source.go (ipcMaxFrameSize, ipcMsgTypeOpus)
- Keep update_opus_encoder_params() for potential future runtime config
Benefits:
- Simpler codebase: -1,734 lines of code
- Better performance: No IPC overhead on embedded hardware
- Easier maintenance: Single audio implementation
- Smaller binary: No embedded audio subprocess binaries
The audio system now works exclusively via CGO direct C function calls,
with ALSA device selection (HDMI vs USB) still configurable via settings.
Audio quality improvements:
- Enable constrained VBR to prevent bitrate starvation at low volumes
- Increase Opus complexity from 2 to 5 for better quality
- Enable DTX for bandwidth optimization
- Enable FEC (Forward Error Correction)
- Add DTX and FEC signaling in SDP (usedtx=1;useinbandfec=1)
Default configuration changes:
- Change default audio output source from HDMI to USB
- Enable USB Audio device by default
- USB audio works on current stable image (HDMI requires newer device tree)
These changes fix crackling issues at low volumes and provide better
overall audio quality for both USB and HDMI audio paths.
Alex P