Input Lag

Understanding Input Lag

Input lag is a critical performance metric for LED displays, particularly in applications requiring real-time responsiveness. Understanding and minimizing latency ensures optimal performance for live events and interactive content.

Measuring Input Lag

**Units:** Typically measured in milliseconds (ms) or frames.

**Frame Reference:**

• At 60fps: 1 frame = 16.67ms
• At 30fps: 1 frame = 33.33ms
• At 24fps: 1 frame = 41.67ms

Latency Sources

**LED Processor:**

• Signal conversion: 1-2 frames
• Scaling operations: 0-1 frame
• Color processing: <1 frame
• Total: 1-3 frames typical

**Receiving Cards:**

• Data reception: <1 frame
• Processing: <1 frame
• Total: ~1 frame

**Additional Equipment:**

• Switchers: 0-1 frame
• Scalers: 1-2 frames
• Matrix: 0-1 frame
• Each device adds latency

Application Requirements

**Virtual Production:**

• Target: <1 frame
• Critical for camera sync
• Requires specialized equipment

**IMAG/Live Camera:**

• Target: <2 frames (33ms)
• Visible lip-sync issues above
• Acceptable delay for most

**Presentations/Playback:**

• Target: <4 frames acceptable
• Not time-critical
• Most systems meet this

**Gaming/Interactive:**

• Target: <1 frame (16ms)
• Feel responsive
• Low-latency mode essential

Reducing Input Lag

**Signal Path:**

• Minimize devices in chain
• Use direct connections
• Avoid unnecessary conversion

**Processor Settings:**

• Enable low-latency mode
• Disable unnecessary processing
• Use native resolution when possible

**Configuration:**

• Bypass scaler if resolution matches
• Disable frame buffer doubling
• Optimize receiving card settings

Measurement Methods

**High-Speed Camera:** Record source and display simultaneously at 240fps+, count frame difference.

**Specialized Tools:** Leo Bodnar lag tester and similar devices provide precise measurements.

**Visual Comparison:** Display moving content, observe delay between devices.

Trade-offs

Reducing latency may require:

• Disabling some processing features
• Lower scaling quality
• Limited color correction
• Compromised image quality

Balance latency requirements with image quality needs for your specific application.