Mastering Color Accuracy with YUV Analyzer: A Practical Guide

YUV Analyzer Pro Tips: Detecting Range, Chroma, and Luma Issues

Quick overview

YUV Analyzer helps inspect video color data by separating luma (Y) and chroma (U, V) components so you can find range, clipping, and color-balance problems that are hard to see in RGB.

Common problems to look for

• Luma clipping: Highlights or shadows crushed when Y values hit 0 or max; watch for flat bright or dark areas.
• Chroma clipping/saturation: U or V channels pegged at min/max causing color loss or blown hues.
• Range mismatch (full vs. limited): Video intended for limited range (16–235) displayed or encoded as full (0–255) — results in washed or overly contrasty images.
• Chroma subsampling artifacts: Color bleeding or loss of detail from 4:2:0/4:2:2 conversions.
• Incorrect color space / transfer matrix: Wrong conversion (e.g., Rec.709 vs. Rec.601) yields hue shifts and incorrect saturation.
• Chroma/tint shifts: Global U/V offsets produce skin-tone or green/magenta casts.
• Banding and posterization: Insufficient bit depth or heavy compression visible as contour steps in gradients, especially in Y.

Practical inspection steps (order to run)

1. Load a representative clip (include highlights, skin tones, darks, and saturated colors).
2. View individual Y, U, V waveform or histogram to spot clipping and distribution.
3. Check combined vectorscope for chroma angle and magnitude (hue vs. saturation).
4. Compare luma waveform against expected range (limited vs full).
5. Inspect per-frame extremes to find intermittent clipping.
6. Toggle color-space/transfer presets (Rec.709/Rec.601/BT.2020) and observe differences.
7. Zoom into areas with fine color detail to reveal subsampling artifacts.

Metrics and visual cues to trust

• Waveform (Y): Peaks at 0 or 235 (limited) or 0/255 (full) indicate clipping.
• Histogram (U/V): Spikes at extremes show chroma clipping.
• Vectorscope: Clusters shifted off skin-line indicate tint/hue issues; overshoot means over-saturation.
• Per-channel difference view: Quickly exposes which channel causes visible artifacts.

Fixes and recommendations

• Apply legal-range scaling or normalize levels when full/limited mismatches are detected.
• Use chroma limiting or soft clipping rather than hard clipping to preserve hue.
• Convert using correct color matrix for source/target (Rec.709 vs Rec.601 vs BT.2020).
• Use chroma upsampling filters with edge-preserving algorithms to reduce subsampling artifacts.
• Add slight denoising before heavy compression to reduce banding, or use dithering for gradients.
• For tint shifts, apply balanced U/V offsets or targeted hue corrections (preserve skin-tones).

Automation & workflow tips

• Create presets for expected color spaces and bit depths to quickly detect deviations.
• Run automated checks that flag frames where Y/U/V hit unsafe extremes or vectorscope distances exceed thresholds.
• Export CSV logs of peak/min values per frame for trend analysis and batch fixes.

Fast checklist before delivery

• Verify full/limited range consistency end-to-end.
• Confirm correct color-space matrix used for conversion.
• Ensure no sustained clipping in Y or U/V across the clip.
• Spot-check skin tones on vectorscope skin-line.
• Test final encode to confirm no new artifacts introduced.