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PRD-local-recording.md: Dual-path architecture for podcast-quality interviews — local lossless WAV recording alongside live call, with sync markers for post-session alignment, resumable upload to a self-hosted mixer service that produces normalized multi-track output. PRD-studio-quality.md: Documents the Opus 32k/48k/64k studio tiers, when to use them, cross-codec interop, and backward compatibility. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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PRD: Studio Quality Tiers (Opus 32k/48k/64k)
Status: Implemented
Studio quality tiers have been added to the wire protocol and all clients.
What Was Added
Wire Protocol (codec_id.rs)
Three new CodecId variants using the 4-bit header space (values 6-8):
| CodecId | Wire Value | Bitrate | Frame | Use Case |
|---|---|---|---|---|
| Opus32k | 6 | 32 kbps | 20ms | Studio low — noticeable improvement over 24k for voice |
| Opus48k | 7 | 48 kbps | 20ms | Studio — excellent voice, captures nuance |
| Opus64k | 8 | 64 kbps | 20ms | Studio high — near-transparent quality |
Quality Profiles
| Profile | Codec | FEC | Bandwidth (with FEC) |
|---|---|---|---|
| STUDIO_32K | Opus 32k | 10% | ~35 kbps |
| STUDIO_48K | Opus 48k | 10% | ~53 kbps |
| STUDIO_64K | Opus 64k | 10% | ~70 kbps |
FEC is set to 10% (vs 20% for GOOD) — studio assumes a good network.
Client Support
| Client | Selection | Status |
|---|---|---|
| Desktop (Tauri) | Quality slider in Settings (8 levels) | Done |
| CLI | --profile studio-64k / studio-48k / studio-32k |
Done |
| Android | Needs codec picker update in SettingsScreen.kt | TODO |
| Web | Needs UI | TODO |
Cross-Codec Interop
All decoder auto-switch paths (call.rs, desktop engine.rs) handle the new codec IDs. A studio-64k client can talk to a codec2-1200 client — the receiver auto-switches.
When to Use Studio Tiers
- Podcast recording sessions: Use studio-64k for best quality (combined with local WAV recording for pristine output)
- Music collaboration: Opus at 48-64k captures instrument harmonics much better than 24k
- Good network conditions: Only useful when bandwidth isn't constrained; the extra bits are wasted on lossy networks
When NOT to Use
- Mobile data: Stick with Auto/GOOD — studio tiers use 2-3x the bandwidth
- High packet loss: Studio profiles use minimal FEC (10%); degraded networks need DEGRADED or CATASTROPHIC profiles with 50-100% FEC
- Large group calls: Each participant's stream multiplies bandwidth; 64k * 10 participants = 640 kbps incoming
Backward Compatibility
Old clients (before this change) will receive packets with CodecId 6/7/8 which they don't recognize. The from_wire() returns None for unknown values, causing the packet to be dropped. Old clients can still send to new clients fine (they use CodecId 0-5). This is acceptable for a pre-release protocol.