TheSigma wrote:Can you describe how your setup is layed out? I understand you have the combiners and all that but how do you have the a51(s) in the signal chain? Are the inputs assigned from a router and the output fed into switcher (VisionMixer)?
You bet!
Just some general background first: in our plant, every source hits a video distribution amplifier; one output of each hits our main router through identical length cables. We set system timing at the router, with the result that sources automatically wind up matching phase at the DAs. We feed several router outputs to the production switcher through matching cables, and the production switcher's internal pulse generator is set up so that internal black and color backgrounds match phase with the router feeds. Finally, we have a bundle that goes from the video DAs to the other production switcher inputs; this bundle is cut to the correct length so that video going from a DA directly to the production switcher arrives at the same phase as the same signal going through the router.
Okay... now for the A51. I'll describe how the original system was wired -- that is, without the combiner option -- which will be closer to what you would be doing.
The A51 has two pairs of composite and key inputs, 1 and 2; each pair is fed from a Di-Tech dual 16x1 video switcher that is remote controlled by the A51. The idea is that the A51 directly controls which key and fill source show up as input 1 or input 2 -- among other things, it will automatically switch sources in coordination with an effect or according to a timeline. At any rate, the feeds going to the Di-Tech switchers come from the main distribution amplifiers. You need to have sources at the Di-Tech matching each other in order to prevent chroma flashing when sources switch; otherwise, the A51 auto-times the inputs.
The A51's video and key outputs go to the production switcher: the video to a primary input, and the key to one of the external key inputs.
Timing and setup are really critical to making the system run right:
1) In the A51's setup menu, adjust the horizontal and subcarrier timing to make it match phase with your other production switcher sources.
2) Feed a good video source into the A51 (if you have a test generator, a flat field is good), and set it to squeeze the picture down to about half size, in the middle of the screen. Set up the production switcher to key the A51 over some other source -- generally, I use the color background set to light grey. Get into the A51 setup menu again and adjust the key timing so that the A51's video lines up exactly with the hole being cut in the video. You might also need to adjust the blanking width if you have a black edge on both sides of the inset.
3) Feed a source of color bars into both the A51's input; on the switcher, set up a horizontal wipe between that same source, and the A51. Set the A51 to make the picture full size and centered (as I recall, hitting "clear" several times will do this). Go back to the setup menu, and adjust the video position (not the phase) to make the A51's picture line up exactly with the direct source. Adjust the black level and video gain to get the luminance values to match on a waveform monitor; then adjust the chroma level (I think they call it boost or EQ) and video phase to make the colors match. By the time you finish, the video going through the A51 should be a very close match to the original source.
4) Once you have all the settings nailed down, copy the current setup to the other three setup memories, and also copy it to a floppy disk. This is especially critical if your memory battery is shot, because all of these settings will revert to something random if the power is turned off.
It's not necessary to have the Di-Tech switchers... we could have fed the A51 inputs directly from our main router, but our production folks wanted the A51 to be able to select the video sources.
One approach that works very well: if you have a switcher with an aux bus (like a Grass Valley 300, for example), you can feed that into the A51... which allows you to send a mix-effect bus into the A51 without worrying about the timing delay.
Gotta fly... we just had a video encoder die.
-- Jeff
