Adaptive quality — auto-adjust resolution and frame rate based on network conditions

[CREVIOS]

Overview

Automatically adjust the remote desktop resolution, color depth, and frame delivery rate based on real-time network conditions. When bandwidth is low or latency is high, reduce quality to maintain responsiveness. When conditions improve, scale back up.

Behavior

```
Network quality Resolution Color depth Frame target
───────────────── ────────── ─────────── ────────────
Excellent (LAN) Native 32-bit 60 fps
Good (<50ms) Native 32-bit 30 fps
Fair (50-150ms) 1280x720 16-bit 15 fps
Poor (>150ms) 1024x768 16-bit 10 fps
Terrible (>300ms) 800x600 8-bit 5 fps
```

Implementation

Step 1: Network quality measurement

Track rolling averages over last 10 seconds:

• RTT latency (from RDP ping/pong or TCP keepalive)
• Frame delivery rate (frames received per second)
• Bandwidth estimate (bytes received per second)

Step 2: Quality controller

```rust
struct QualityController {
current_tier: QualityTier,
latency_samples: VecDeque, // last 30 samples
bandwidth_samples: VecDeque,
}

enum QualityTier { Excellent, Good, Fair, Poor, Terrible }

impl QualityController {
fn evaluate(&mut self) -> Option {
let avg_latency = self.latency_samples.iter().sum::() / len;
let new_tier = match avg_latency {
l if l < 20.0 => Excellent,
l if l < 50.0 => Good,
l if l < 150.0 => Fair,
l if l < 300.0 => Poor,
_ => Terrible,
};
if new_tier != self.current_tier {
return Some(QualityChange { ... });
}
None
}
}
```

Step 3: Apply changes

• Resolution change: send RDPEDISP display update PDU
• Color depth: renegotiate via capabilities exchange (may require reconnect)
• Frame rate: client-side throttle (skip N frames)

Step 4: UI indicator

Show current quality tier in the toolbar:

• Green dot: Excellent/Good
• Yellow dot: Fair
• Red dot: Poor/Terrible
• Tooltip: "Auto: 1280x720 @ 15fps (latency: 95ms)"
• Settings: disable auto-adjust, set manual quality level

Files to create/modify

• `src-tauri/src/rdp/quality.rs` — new module
• `src-tauri/src/rdp/session.rs` — integrate quality controller
• `src/components/session/SessionToolbar.tsx` — quality indicator

Priority: P2 — significant UX improvement for remote connections