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SheerVideo User Manual

Sheer Settings
Pixel Format Conversion

The Sheer codecs are designed to be strictly nondestructive, and try to prevent the user from inadvertently losing image information by accidentally choosing the wrong codec and thus reducing the sample precision, changing the chroma sampling, or converting the color space without increasing the sample precision accordingly.

However, it is sometimes necessary to convert between different representations, even if such a conversion is impossible without some information loss. For example, when combining video and film elements, when using a tool which does not operate in the desired pixel format, or when outputting a low-bandwidth version for review or distribution, such conversion is inevitable.

To deal with such cases, the Sheer encoders allow the user to explicitly sanction destructive conversion.

In the Pixel Format Conversion section of the Sheer Settings dialog box, select one of the following radio buttons:

  • Perfect Perfect, to accept only pixel formats that can be encoded perfectly.
  • Best Best, to encode using the best possible method even if the pixel format cannot be converted without information loss.

Synchromy To convert between RGB and Y'CbCr color spaces, SheerVideo uses BitJazz's patented Synchromy™ technology, (US Patent 7,659,911) which is more accurate than any other color-conversion method. In particular, Synchromy converts with absolutely no information loss between the original and final images in the following workflows:

  • Y'CbCr[A] 8bv 4:4:4[:4] → Sheer RGB[A] 10bf → Y'CbCr[A] 8bv 4:4:4[:4]
  • Sheer RGB[A] 10bf → Y'CbCr[A] 12bv 4:4:4[:4] → Sheer RGB[A] 10bf
  • Sheer RGB[A] 8bf → Y'CbCr[A] 10bv 4:4:4[:4] → Sheer RGB[A] 8bf
  • RGB[A] 8bf → Sheer Y'CbCr[A] 10bv 4:4:4[:4] → RGB[A] 8bf
  • Sheer Y'CbCr[A] 10bv 4:4:4[:4] → RGB[A] 12bf → Sheer Y'CbCr[A] 10bv 4:4:4[:4]
  • Sheer Y'CbCr[A] 8bv 4:4:4[:4] → RGB[A] 9bf → Sheer Y'CbCr[A] 8bv 4:4:4[:4]

Note that if pixel-format conversion does actually result in information loss, the self-check will fail, so self-check mode must also be turned off to permit imperfect conversion.

For applications using the standard QuickTime Compression Settings dialog box, unfortunately, you must use Best Conversion for all Sheer Y'CbCr[A] codecs except Sheer Y'CbCr[A] 10bv 4:4:4[:4], because the preview image in the QuickTime Compression Settings dialog box requires RGB 8b encoding, and perfect conversion from RGB[A] 8bf to Y'CbCr[A] 8b or 4:2:2[:4] is impossible, even with Synchromy.

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