DVCAM is lossily compressed Y'CbCr 8bv 4:1:1 (NTSC) or 4:2:0 (PAL).
However, for a DVCAM shooter, 8-bit uncompressed typically means a Y'CbCr 8bv 4:2:2 pixel format, because 4:1:1 and 4:2:0 are planar formats, in which the entire luma (Y') image is stored separately from the chroma (Cb,Cr) channels, making them awkard to use for capture, editing, or playback.
SheerVideo includes both RGB[A] and Y'CbCr[A], both 8b and 10b, both 4:4:4[:4] and 4:2:2[:4] codecs. It does not, as yet, include any 4:1:1 or 4:2:0 codecs.
As defined by the actual image bits, uncompressed Y'CbCr 8bv 4:2:2 and Sheer Y'CbCr 8bv 4:2:2 are identical.
But there's a substantial difference in size: the Sheer data averages around 42% the uncompressed data rate, even for high-detail real-world footage.
More significantly for production schedules, there's a substantial difference in speed. For uncompressed video, the main system bottleneck is usually data transfer rate. Because SheerVideo generally runs faster than the data transfer rate, encoding or decoding Sheer typically takes only 42% as long as inputting or outputting uncompressed video. If your system is fast enough for real-time uncompressed SD, you won't notice notice a difference in simple real-time capture or playback, but Sheer's lower overhead makes it possible to apply more effects in real time, and can significantly speed up non-real-time operations.
Finally, SheerVideo also includes Synchromy color-conversion technology, which is more accurate than any other color-space converter out there. So if you're editing your DV with RGB tools, you get better results.
Andreas Wittenstein
BitJazz Inc.
[
www.bitjazz.com]
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