Posted by Toby on 09/20/06 02:29

Some of you might remember our discussion about dropouts in DV a couple of
months ago. I found something rather interesting in this month's IBE:

"MPEG-2 video uses 4:2:0 sampling (one Cb sample, one Cr sample and four Y
samples) for each pixel (except 4:2:2 and High profiles). Samples are then
grouped into blocks (or squares) of 16 x 16 pixels, a macroblock. If the
data from any of these samples is lost, the decoder cannot reproduce the
block.. When this occurs in an I frame, subsequent B and P frames may also
be affected, causing the data corruption to continue until the next good I
frame, which could be a second or more in long GOP encoded data. These
errors are very apparent to the viewer. These errors are usually a result of
transmission problems (RF or IP) or 'drop-outs' in videotapes."

So obviously there are drop-outs in DV, which--while rarer than in analogue
perhaps--can be egregious and are of concern to the industry.

Toby

[Back to original message]