karl@sugar.UUCP (Karl Lehenbauer) (06/26/87)
(...had trouble posting this as a followup, sorry.) In article <2026@cbmvax.cbmvax.cbm.UUCP>, hedley@cbmvax.cbm.UUCP (Hedley Davis) writes: > In article <1171@osiris.UUCP> phil@osiris.UUCP (Philip Kos) writes: > >Question for all you serious broadcast people out there: I imagine the > >original chroma key hardware was analog. Is it still done that way, or is > >it done digitally now? ... > ... > I've heard of full digital units which do digitize the incoming video. All of the big video switchers have, since about 1979, digitized video as part of their processing. The ability to squeeze a full screen image into a smaller area in a TV picture without cropping or camera tricks requires (I believe) such a unit. These units can do all sorts of mapping of TV images onto (apparent) 3D surfaces, "digital strobing" (a sort of video echoing), "pixilazation" (averaging blocks of pixels to reduce the apparent number of pixels) and many other things. Specifically regarding how chroma keying is done now, analog is still the norm for most places, but the ultimate chroma keyer is called UltiMatte (TM). It's digital and smart, so its keys don't leave those annoying edges around the weatherman and glitches in his hair when he's in front of the blue screen. The Cars video "You Might Think" and the California Cooler commercials use extensive digital video effects and are a good example of how "clean" the images generated by these units are. -- bbs: (713) 933-2440 voice: (713) 933-9134
john@datacube.UUCP (07/02/87)
> Written 8:22 pm Jun 25, 1987 by karl@sugar.UUCP in comp.graphics */ > ---------- "Broadcast Digital Video Effects" ---------- */ > >... but the ultimate chroma keyer is called UltiMatte (TM). It's >digital and smart, so its keys don't leave those annoying edges around the >weatherman and glitches in his hair when he's in front of the blue screen. >..... >bbs: (713) 933-2440 voice: (713) 933-9134 I believe you are incorrect about the UltiMatte. It is a strictly analog beast. As I recall the unit croma keys an RGB source over another RGB source. It can also key a composite source (NTSC or PAL) over another composite, but to do this it requires RGB for the forground. It uses the RGB from the forground to develop an analog "Keyhole" signal. I believe the key signal is proportional to the amount of blue in the signal where there is no green or red present. The key signal is then multiplyed against the background to make the cutout. The key signal is also subtracted from the blue channel on the foreground, removing the unwanted blue background from the forground image. The processed forground and background are then simply added together to make the final image. John Bloomfield Datacube Inc. 4 Dearborn Rd. Peabody, Ma 01960 617-535-6644 ihnp4!datacube!john decvax!cca!mirror!datacube!john {mit-eddie,cyb0vax}!mirror!datacube!s, b
shep@datacube.UUCP (07/02/87)
>All of the big video switchers have, since about 1979, digitized video >as part of their processing. Wrong. "big video switchers", the most sophisticated being the multiple M/E switchers used in post-production, have video paths that are almost entirely analog. These switchers are frequently connected to digital special effects machines like Ampex's ADO. ADO digitizes incoming video and key signals, manipulates it digitally, then converts it back to an analog singal for the switcher. Someday "all digital" studios will be widespread. Not today. >The Cars video "You Might Think" and the California Cooler commercials >use extensive digital video effects and are a good example of how >"clean" the images generated by these units are. True. But truth is stranger than reality: I worked at Charlex where both those reels were produced and although both spots have the sharp "Charlex" look, their posting techinques couldn't be more different. The Car's piece was done by rolling a half dozen quarter million dollar tape machines in sync to produce an end result that was only second generation. The CC commercial was done using the digital keying of the Abekas A62 digital disk recorder. Both techniques result in multi-layer opticals that don't suffer from degradation; the latter currently being all the rage in post houses worldwide. Shep Siegel Datacube Inc. DSP Products Group 4 Dearborn Rd. Peabody, Ma. 01960 UUCP: shep@datacube.COM VOICE: (617) 535-6644; FAX: (617) 535-5643; TWX: (710) 347-0125