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Testcard PNG Assets

The pal-png and ntsc-png folders contain standard PNG images for PAL and NTSC test material. These are single-frame images sized to the active picture area only and use normal RGB pixel data. The encoder converts PNG RGB to YUV using ITU-R BT.601 coefficients.

The files included in the folders (testcard-images/pal-wrwetzel-png and testcard-images/pal-wrwetzel-png) were kindly provided by Bill Wetzel and permission has been granted to the project to distribute these files for use with ld-decode and its associated projects under a GPLv3 license.

For more information about the testcard images (and additional images for other television formats) please visit:

wrwetzel.com

Files

PAL (720×576)

  • PAL-720x576-Check-Composite.png — composite test check pattern
  • PAL-720x576-Color-Step-Lin-Magenta.png — linear magenta color step
  • PAL-720x576-Geometry-Checkers-32.png — 32px checker geometry pattern

NTSC (720×480)

  • NTSC-720x480-Check-Composite.png — composite test check pattern
  • NTSC-720x480-Color-Step-Lin-Magenta.png — linear magenta color step
  • NTSC-720x480-Geometry-Checkers-32.png — 32px checker geometry pattern

Pixel format & decoding

  • Color type: RGB recommended. Palette/gray inputs are automatically converted to RGB; alpha is stripped.
  • Bit depth: 8-bit per channel recommended (16-bit PNG is reduced to 8-bit internally); values 0–255 are expanded to 16-bit by value16 = value8 × 257.
  • Layout: Row-major scanlines, no padding between rows (standard PNG behavior).
  • Color space: Treated as generic RGB and converted to YUV with BT.601. Embedded gamma/ICC are not applied.

Required dimensions

  • PAL: 720 × 576
  • NTSC: 720 × 480 (matches provided assets)

If the image dimensions do not match the expected system, loading fails with a clear error (PNG dimensions mismatch) and encoding aborts. Provide PNGs at the exact active-picture size.

YAML usage

Example PAL project using a PNG image repeated for 10 frames:

name: "PAL PNG Check Composite"
description: "PAL encoding using PNG testcard image"

output:
  filename: "test-output/pal-png-check.tbc"
  format: "pal-composite"

laserdisc:
  standard: "none"
  mode: "none"

sections:
  - name: "Check Composite"
    duration: 10
    source:
      type: "png-image"
      file: "testcard-images/pal-png/PAL-720x576-Check-Composite.png"

NTSC is identical except format: "ntsc-composite" and the file path under ntsc-png (720×480).

Notes

  • Images contain only the active picture region; the encoder adds blanking/VBI according to the selected video system and standard.
  • For strict test reproducibility, prefer 8-bit non-alpha PNGs sized exactly as above.
  • If you need flexible inputs (scale/pad/crop to fit), this can be added via a future YAML option (e.g., fit: scale|pad|crop).