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SheerVideo FAQ
Power: Introduction

How is compression power measured?

How powerful is SheerVideo?

SheerVideoHow powerful is SheerVideo?

For real-world photo-quality imagery, as measured on high-detail standard test data, SheerVideo has an average compression power of 2.20 for RGB 8b; 2.84 for Y'CbCr 8bv 4:4:4; 2.43 for Y'CbCr 8bv 4:2:2; and 2.32 for Y'CbCr 8bw 4:2:2.

As a non-destructive codec, SheerVideo's compression power is limited by the intrinsic information content (entropy) of the video. For example, a blue sky will compress much better than a colorful meadow, and pure white noise can't be compressed at all.

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SheerVideoHow is compression power measured?

The compression power, also known as the compression ratio, is defined as
compression power = uncompressed size / encoded size
Note that a compression power of 1.0 means no compression at all. As a ratio of two sizes, compression power is a pure number, lacking any measurement unit, so it is common to put an 'X' or a ':1' after the number, as in "2.0X" (two-times power) or "2:1" (two-to-one power).

In video compression research, the compression power is normally measured on a set of standard reference set of real-world test data consisting of 24 high-detail photo-quality uncompressed images, each with a resolution of 768 x 512 RGB pixels at 8 bits per channel, originally published in uncompressed TIFF format on Kodak PhotoCD PCD0992 (Copyright Eastman Kodak).

Be very skeptical of any compression-power claims based on a nonstandard set of test images, especially if the images are unavailable for third-party verification, or if the test images are unspecified.

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