mrd@ecs.soton.ac.uk (Mark Dobie) (01/10/90)
We are trying to connect our VCR output to the video input of the Philips 410 and then use the RGB and sync output from the 410 to drive a monitor. Essentially we want to use the 410 to convert the VCR video signal to RGB plus sync signals. We get the RGB signals and the sync, but the sync is unstable. Can anybody help us? Here's what we've tried. If you don't know about the Philips 410 it won't make much sense. For input to 410: VCR out connected to CVBS in. Other CVBS IN terminated or looped to sync IN with and without other sync IN terminated. For output from 410: RGB from SCART socket and sync from sync OUT all connected to various combinations of monitor inputs. This works fine if we just play a laserdisc, but when we tell the 410 to use its CVBS input instead we get the problem with the sync. Mark Dobie University of Southampton mrd@ecs.soton.ac.uk -- Mark Dobie University of Southampton mrd@uk.ac.soton.ecs
brwk@doc.ic.ac.uk (Bevis King) (01/12/90)
In article <2196@ecs.soton.ac.uk> mrd@ecs.soton.ac.uk (Mark Dobie) writes: >We are trying to connect our VCR output to the video input of the >Philips 410 and then use the RGB and sync output from the 410 to drive >a monitor. Essentially we want to use the 410 to convert the VCR video >signal to RGB plus sync signals. > >We get the RGB signals and the sync, but the sync is unstable. >Can anybody help us? Ok - I think the answer to this question is fairly straight forward. The syncs from the video disc players CVBS to RGB convertor is unstable because the output of the VCR is unstable. Video disc players are at present unique among domestic/industrial video equipment in that they store the full-bandwidth video signal without modification or recoding. This means that the signal is recorded syncs, monochrome picture and colour burst all as one chunk. Due to this method of recording, the raw output from the laser pickup and FM decoder contains the colour sub-carrier as its highest frequency component. The naturally unstable timebase of any replay system affects the sub-carrier particularly badly - VCRs get round the problem by recoding the colour burst to a lower frequency, minimising the instability. Video Disc Players can't, and so they always have a built-in timebase corrector to sort out the problems. It's important to note that the video disc internal timebase correctors are simpler than the free standing devices for video cassette recorder usage in that they do not attempt to correct for drop-outs to the same extent. Anyway, the bottom line is that the output from a video disc player will have a rock steady timebase and the CVBS -> RGB decoder will rely on those syncs being stable, merely stripping them off and using them. A VCR without a time base corrector will be all over the place! (Just try comparing the pictures of a video disc player and a VCR on a monitor with cross-pulse - uggggh!) So the moral of this story is: a) get a time base corrector for the VCR b) get a CVBS -> RGB decoder that cleans up the syncs while its about it. Hope this helps. Regards, Bevis Bevis King, Systems Programmer | Email: brwk@doc.ic.ac.uk Dept of Computing, Imperial College | UUCP : brwk@icdoc.UUCP 180 Queens Gate, London, SW7 2BZ, UK. | Voice: +44 1 589 5111 x 5085 "Never argue with a computer" ... Avon (Blake's 7)