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Old 7th October 2014, 14:15   #11  |  Link
pandy
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Join Date: Mar 2006
Posts: 1,049
Quote:
Originally Posted by Ghitulescu View Post
If the s-video output of the source is ok (remember that only S-VHS has S-video (there is a single exception, out of millions of models), so any device that gets S-video out of a VHS deck actually tricks the capture), then it may be that either the cable is broken (one reason why S-video never made it to the studios) or the filters (which may be as little as ferrite pearls) are defective/bad/too aggressive.

There are lots of devices that yielded a better image with composite rather than with S-Video, in particular at conversions.
Guys, most of VCR's (if not all of them) record chroma in separate part of spectrum - they can have S-Video (or rather separate Y and C output) by physical construction of signal path.
S-Video connector appear together with S-VHS - as it was requirement to further improve video quality but there is nothing against to have S-Video in non S-VHS VCR.
In fact everyone can modify already own VCR without S-Video and add S-Video output.

Feeding CVBS to S-Video mean for capture card only that card doesn't try to separate chroma and luminance (this can be performed on many ways) - in fact luminance and chrominance separation can be performed in software way better than internal capture HW method.
http://www.jim-easterbrook.me.uk/pal/ - thread about software TBC partially cover this aspect - Bt878 and compatible cards can be programmed to capture 4*Fsc video as grayscale with H-sync and burst - rest of processing can be done in software even offline.

Side info - this is purely theoretical as real VHS have limited bandwidth and in many situations chroma and luma occupy CVBS in non overlapping way (Y bandwidth is usually well bellow 3.2MHz where chrominance carrier is 4.43 and bandwidth for U&V is around .5MHz ie 4.43 +-.5Mhz - but even with full chrominance legal bandwidth i.e. 1.25 - 1.5Mhz they should be quasi non overlapping for ordinary VHS as 4.43 +-1.5MHz is in worse case scenario 2.93Mhz for Y).

Last edited by pandy; 7th October 2014 at 14:27.
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