Convert composite to s-video

[tmac]

Anyone had experience with above? I have found a gadget which is used for converting audio to digital, but also converts composite to svideo. Will I gain anything as my vcr only outputs composite, but my capture card has a svideo in port?
Previous post covers the reasons why I am trying to do this. My scart adaptor has svideo out but it only works on the tv. I am guessing that the scart is giving out composite only.

[reepa]

If, at any point, the signal is in composite form, the resolution is premanently lost. You can't recover the sharpness by converting it back to s-video. Unless you have an s-video out (or scart or component), you don't gain anything by converting.

[fellaw]

Converting composite to S-Video outside the card doesn't make sense. The A/D converter of the card(e.g. BT8x8 or SA7134) does this job better than any external device, simply because the signal loss is higher this way than inside the chip. The chip seperates the Y/C planes anyway, so why add insult to injury by seperating them externally? Those cheap scart adapters with an S-Video input/output use the composite signal of the scart for color and the red signal for luminance. There is no real S-Video with those kind of adapters. However, if your VCR/receiver is capable of RGB, an external RGB to S-Video Converter COULD make sense, if it's of good quality.

[Joe Fenton]

The main reason for converting composite to SVideo outside the video card is that most video cards have a cheap-ass separator. They usually just knotch filter the luma and bandpass filter the chroma. This is easy and cheap, but gives average results.

An external converter can have a comb filter, or something even more sophisticated at separating the luma and chroma. That is what a GOOD external converter will do.

So to answer the original question, if the external converter is GOOD and does good separation AND your card does CHEAP separation, it would be in your best interest to use it. Otherwise, it really makes no difference.

[Arachnotron]

Actually, modern cards (CX23881 and Philips SAA7134 based ones) have good 2D adaptive comb filters.

Even BT878 and SAA7113 based devices have reasonable comb filters, though not adaptive. I made some comparisons, and the difference is not nearly as dramatic as you would expect. Simply avoiding composite is better, since even for the best devices s-video is much better than composite.

Many external video processor devices are based on philips SAA series chips, which use the same adaptive comb filters as the SAA713x chips found on philips based tv cards.

To get better comb filters then those found on those TV cards you are talking about extremely high end equipment. It would be cheaper to simply buy a s-VHS VCR.

[Arachnotron]

by the way, I also own a device which will convert composite to s-video. It's purpose is to take out VBI data like macrovision and replace it with blank leven signal.
It operates purely digital, but I found that the y/C separation was based on a simple analog band-pass filter, since the main chip only operated on separate luma and chroma signals (some philips TDAA chip, forgot which one). Nice for s-video input, but composite looked terrible.

So be carefull about what a device like that really does with the signal.

[tmac]

Thanks for all the help. Decided to buy svhs vcr on ebay. Can I play my tapes through that as is or would it be better to retape them on to svhs tapes?

[Arachnotron]

S-VHS VCR's play normal tapes just fine. In fact, if you use the s-video output to capture the result looks even better then the same tape played back on a VHS VCR.

Also, S-VHS VCR's often have nice stabilising circuitry like TBC's which also work with VHS tape playback.

Allways avoid tape to tape transfer involving a VHS-VCR (composite) source since you introduce extra chroma shifts and add an extra decomb filter step with all the quality loss involved.

[tmac]

MANY THANKS