SheerVideo's self-check mode, accessible through a radio button in the Algorithm section of the Sheer Settings dialog, verifies each compressed video frame by decompressing it to the original pixel format and comparing the restored frame to the original. You should only use self-check mode when no pixel-format conversion is required (see the section on Sheer Codecs) or when perfect pixel-format conversion is possible (see the section on Pixel Conversion).

Self-check mode must be turned off to allow destructive conversion. Unfortunately, in applications which use the standard QuickTime Compression Settings dialog box, you must use One-way Mode 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 support, and even with Synchromy technology, RGB[A] 8bf pixel formats cannot be perfectly converted to any Y'CbCr[A] formats of precision less than 10 bits or to perfectly convert RGB[A] images back to 4:2:2[:4] chroma-subsampled images.

At the top of the Algorithms section, select one of the following radio buttons:

• One-way (faster), to have SheerVideo just encode the video. This is the default value.
  
• Self-check (safer), to have SheerVideo encode, decode, and compare the result, to verify that each frame is encoded with perfect fidelity.
  

Note that SheerVideo is so fast compared to other system bottlenecks that you may not notice any slowdown in using the self-check mode, especially for frames small enough to fit in the CPU cache.