I used to work in the area of digital video compositing and know how Keying (or more precisely Matting), masking and compositing works as I worked for the company that invented it 30 years ago. In general it only works inside a pure digital signal where the picture is converted into colour difference parameters, usually referred to as 4:2:2:4 (360mbs bitrate, which is an 8-bit signal) or when used in high end applications or film is 4:4:4:4 (720mbs bitrate, which is the truer 10-bit signal).Originally Posted by Gerry
Yes
I also believe that Elvis is dead, the Americans landed on the Moon and Princess Dianna wasn't an alien - just call me gullible ;D
The footage shown is in NTSC which is a what the American's use for their homeland transmission. (BTW - if you believe your "digital" TV at home is actually fully digital, you may be in for a bit of a shock). You cannot do any of the work spoken about in NTSC or even in a more modern MPEG format. The signal has to be converted to digital colour difference parameters before it can be manipulated in the way demonstrated which is done inside digital framestores. It would then have to be re-encoded back to the composite TV signal in this case NTSC. All of which is technically possible, however the resultant artifacts would be so obvious as to make it un-useable. Also, Keying is a studio or post production tool but it has to have a signal that equates to the cutout before it can be used. In the studio this uses complexities such as blue or green screen matting which you may have seen on TV (technically this is called Chromakeying). In the field that would mean a second camera just to use for a key signal as video cameras do not produce this on their own. To do what they are discussing, you would have to have had a second camera perfectly aligned with the video camera just to produce a Key (or Matte).
The possibility this is sort of kit was on the ground during 9/11 or available to be used live is, err, nil.
So, in short, I agree with Gerry ;D ;D ;D
