Troubleshooting Common YuvViewer Issues: Playback, Color, and Resolution

How to Use YuvViewer to Inspect YUV Frames and Pixel DataYuvViewer is a lightweight, Windows-based utility for opening raw YUV video files and inspecting individual frames, pixel values, color planes, and chroma subsampling effects. It’s commonly used by video engineers, codec developers, researchers, and enthusiasts who need to verify YUV conversions, analyze color sampling, and debug processing pipelines. This guide walks through installing YuvViewer, opening files, interpreting color planes, using tools for pixel inspection, adjusting display settings, working with different YUV formats and chroma subsampling, and practical workflows for debugging and analysis.

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What YuvViewer does and when to use it

YuvViewer is designed specifically for raw YUV formats (files with no container, such as .yuv, .y, .iyuv, or raw dumps from encoders). Unlike general-purpose media players, YuvViewer exposes Y, U, and V planes individually, shows pixel numeric values, and supports a wide range of subsampling patterns and bit depths. Use it when you need to:

• Verify that a YUV file uses the expected pixel format, resolution, and subsampling.
• Inspect pixel values to check color conversion, fixed-point rounding, or quantization.
• Compare original and processed frames to find processing artifacts.
• Learn how chroma subsampling affects color detail.

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Installation and first-run setup

1. Download YuvViewer: obtain the latest release from the developer’s distribution page or a trusted archive. The app is a portable Windows executable; installation typically means unzipping the package to a folder.
2. Place sample YUV files in an accessible folder. If you don’t have any, generate one from FFmpeg:

   
   ffmpeg -i input.mp4 -pix_fmt yuv420p -f rawvideo output.yuv 

   Replace yuv420p with the desired pixel format.

3. Run yuvviewer.exe. If prompted by Windows, allow it to run.

On first run, YuvViewer may ask for file parameters when opening a raw YUV file—provide width, height, pixel format, and bit depth.

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Opening a YUV file and configuring basic parameters

Because raw YUV files lack headers, YuvViewer needs these parameters:

• Width and height (e.g., 1920×1080)
• Frame rate (optional for stepping; many users set 25/30/60)
• Pixel format (common values: yuv420p, yuv422p, yuv444p, nv12, uyvy, yuy2)
• Bit depth (8-bit, 10-bit packed/planar variants)

Steps:

1. File → Open → select your .yuv file.
2. In the dialog, enter width and height.
3. Choose the correct pixel format/subsampling. If unsure, try likely formats and inspect plane sizes.
4. Set bit depth. For 10-bit files, choose whether they’re packed or planar.

If frames appear distorted or colors wrong, you likely selected incorrect subsampling or bit depth—try alternatives.

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Understanding Y, U, and V planes

YUV separates luma (Y) from chroma (U and V).

• Y (luma) contains brightness information and typically has full resolution.
• U and V (chroma) contain color difference signals and may be subsampled (less resolution) depending on format:
  • YUV420: U and V at half horizontal and half vertical resolution (⁄₄ pixels)
  • YUV422: U and V at half horizontal resolution only (⁄₂ pixels)
  • YUV444: U and V at same resolution as Y (full color resolution)

In YuvViewer you can:

• Toggle display of Y, U, or V separately to inspect plane content.
• View chroma planes to find color noise, shifted alignment, or chroma artifacts from compression or scaling.
• Observe that luma contains most fine detail, while chroma shows color regions and edges differently due to subsampling.

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Pixel value inspection and overlays

YuvViewer provides tools to inspect numeric pixel values and overlays:

• Pixel readout: hover or click to see Y, U, V values at a coordinate.
• Numeric display typically shows 0–255 for 8-bit or scaled values for higher bit depths.
• Difference view: load a second file or frame and use subtraction to highlight changes—useful for encoding comparisons.
• Histogram and waveform scopes (if available in your version): analyze luminance distribution and clipping.

Practical checks:

• Verify neutral gray: for a neutral RGB gray pixel, U and V should be near their center values (typically 128 for 8-bit).
• Detect bad range: values <= 16 or >= 235 often indicate limited range (video range) clipping; full range uses 0–255 for 8-bit.

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Working with chroma subsampling and alignment issues

Common problems:

• Chroma shift: U/V planes misaligned by one pixel or one line cause color shifting. Toggle chroma plane display to reveal misregistration.
• Incorrect subsampling selection: choosing yuv420 when file is yuv422 will distort color blocks. Compare expected plane sizes: for 1920×1080 yuv420, each chroma plane is 960×540; for yuv422, chroma planes are 960×1080.
• Interleaved vs planar: formats such as YUY2 interleave Y and chroma—YuvViewer will present those differently; ensure correct format selection.

How to check alignment:

• View a high-contrast edge (black/white) and examine chroma planes—if chroma edge is offset, adjust plane offsets or check for packing variants.
• Use pixel readout on the same coordinate between Y and U/V to ensure consistent sampling positions.

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Bit depth, endianness, and packed formats

• 8-bit: simple one byte per sample per plane (most common).
• 10-bit and higher: may be stored in packed formats (e.g., 10-bit packed into 16-bit words or specialized packing). YuvViewer asks for bit depth and packing—choose correctly or values will appear incorrect.
• Endianness matters for multi-byte samples—select the correct byte order if values seem swapped.

If values look too large or too small, re-open the file with a different bit-depth/packing option.

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Comparing frames and spotting artifacts

Workflows:

• Side-by-side comparison: open original and processed files in two windows or use YuvViewer’s compare function if present.
• Frame subtraction: subtract one frame from another to visualize differences—useful to locate block boundaries, banding, or registration errors.
• Zoom and inspect: zoom into suspected areas and read pixel values to quantify artifacts (e.g., small chroma offsets, quantization steps).

Common artifacts and their likely causes:

• Blockiness: coarse quantization in compression — visible in Y and sometimes in chroma.
• Chroma bleeding: smoothing or mismatch in chroma; check subsampling and filtering steps.
• Banding: low bit depth or aggressive compression—visible in Y especially in gradients.

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Practical examples

1. Verify YUV420 export from FFmpeg:

   • Export: ffmpeg -i clip.mp4 -pix_fmt yuv420p -f rawvideo out.yuv
   • Open in YuvViewer: width/height = clip resolution; pixel format = yuv420p; bit depth = 8.
   • Confirm chroma plane sizes are half horizontally and vertically.

2. Debug color cast after color conversion:

   • Load original and converted files.
   • Inspect U/V center values on neutral patches—if they’re offset from center (128), the conversion matrix or offset may be wrong.

3. Find chroma misalignment after scaling:

   • Open the scaled YUV and the reference.
   • Toggle chroma planes, zoom to edges, and check if chroma edges align with luma edges.

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Tips, tricks, and pitfalls

• Keep a short sample file for quick tests (a few frames). Large raw files are slow to open and navigate.
• If frames look vertically compressed or stretched, check width/height order and whether the file uses interlaced storage.
• For unknown formats, estimate file size: file_size / (width*height) gives bytes per frame; compare to expected bytes for candidate formats to infer subsampling and bit depth.
• Use FFmpeg to reconvert or extract specific frames for further testing:

  
  ffmpeg -s WxH -pix_fmt yuv420p -i input.yuv -vf "select=eq(n,10)" -frames:v 1 frame10.png 

  Replace WxH with widthxheight.

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Alternatives and complementary tools

YuvViewer excels at quick inspection. For deeper signal analysis, consider:

• FFmpeg (conversion, extraction)
• VQMT or MSU tools (quality metrics)
• VirtualDub (filters and frame analysis on Windows)
• Python scripts with numpy and image libraries for batch pixel analysis

Comparison table:

Task	YuvViewer	FFmpeg	Python (numpy)
Quick plane inspection	Excellent	Limited	Good (custom)
Batch numeric analysis	Limited	Excellent (with scripts)	Excellent
Format conversion	No	Excellent	Good (via wrappers)
Visual diff/subtraction	Good	Command-line only	Excellent (custom displays)

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Summary

YuvViewer is a focused tool to inspect YUV frames, understand chroma subsampling, and read pixel values—essential for debugging color conversions, alignment, and compression artifacts. Correctly specifying resolution, pixel format, subsampling, and bit depth is vital. Use YuvViewer for quick visual and numeric checks, and combine with FFmpeg or scripting when batch processing or conversions are needed.