> According to it WSS should be present on all three RGB signals instead > of the composite signal. But maybe TVs don't actually work that way.
That's what I found. I was working to the ETSI spec (EN 300 294) but interestingly that doesn't mention which signals you might want to add the WSS pattern to. I wonder if the document you refer to is describing the situation where you might have just R, G, and B (with sync on green) rather than the SCART case where you've got RGB plus CVBS. I guess it's normally quite reasonable for a TV to look at the CVBS only, since it's supposed to have the picture on it all the time. Certainly, all the TVs I've tried only look there, much to my annoyance, having spent some time perfecting my WSS signal! I was further annoyed when I moved to a new system with a unichrome chipset and found that the TV encoder on that board blanks line 23 in its entirety! My solution in the end was a special SCART lead that connects to the machine's serial port via a network of resistors diodes and allows me to drive pin 8. > WSS for NTSC has a few additional problems: > - We'd have to increase the active video to 487 lines to get both WSS > lines included. > - The WSS signal is specified as to be '0' at 0 IRE and '1' at 70 IRE. > We can't generate 0 IRE due to the 7.5 IRE pedestal. I suspect neither of those issues would be of great concern in practise. The receiver must tolerate errors in receiving the code anyway and will probably be entirely happy receiving only every other one. The amplitude error is unlikely to be a problem either. However, it's clearly not ideal as it wouldn't meet the spec. Mark _______________________________________________ directfb-users mailing list [email protected] http://mail.directfb.org/cgi-bin/mailman/listinfo/directfb-users
