Y/C Combs, DNR and Twin Perfect

Television video signal is a combination of Luminance (Y) and Chroma (C) information into one signal. A Composite (or combined) version of these two signals on a single set of wires is called a video signal, it includes (no) audio or sound information.

Normally the seperation between the Y and C components of the video signal are distinct enough to recreate the video without error.. however the signal degrades over long wires as the Chroma information "smears" into the Luminance information effecting picture quality.

To preserve the Y and C components over long wires or poor quality wiring cables, it is better to keep the two seperate on two distinct signal pair wire sets. The S-Video standard was created to do this, and includes four total wires that are two sets of wire pairs. One pair carries Y signal, One pair carries C signal.

S-Video is a "wiring standard" and really has nothing to do with the "S" in S-VHS.

The "S" in S-VHS stood for "Super" and indicated more horizontal dot resolution or perceived Television Vertical Line (counts) also known as "TVL" .

Strictly speaking.. a Black & White picture of only Luminance information could be S-VHS and would have zero benefit over an S-Video cable.. they are entirely two different things.

S-VHS is about horizontal (across the scanline) dot resolution

S-Video is about (preserving) accurate Color information that might be lost and might destroy perceived horizontal dot resolution in the process of carrying the signals a short distance from the VHS player to the Television.

People often confuse or conflate the actual meaning of the two by saying one may effect the other.. in the final result.. the picture..  which is true.. but for different physical reasons that only (sound) like they are related.. in reality they are unrelated.

A Comb filter is used to "extract" the Y from the C information from a "Composite" video signal.

The video signal is (stored) on the Tape in a "Composite" signal format.

All S-Video VHS players have a Comb filter.

When the Tape is played back the Composite signal extracted from the Tape can be handled in one of two ways.

The Composite signal can be placed on a single wire pair and output to Television over a Composite connector, or the  Composite signal can be [broken down using a Comb filter] into a seperate Y and C signal and put individually on seperate wire pairs and output over an S-Video connector.

The Composite connector will provide a better signal to a Television than an RF connection. The Television will have less signal losses and produce a better picture.

The S-Video connector will provide a similar, but even better picture because there will be less Chroma crosstalk with the Luminance signals over the length of the connector from the VHS player to the Television.

Comb filters also offer the "opportunity" to improve the signal quality with filters and amplifiers tuned and customized to work on Luminance (Y) and Chroma (C) signals seperately which exist at different frequencies and are vulnerable to degredation in different ways. Analog and Digital "noise reduction" can be used to "process" the video signal recovered from the tape before it is output to the Television.. and this is called a [ processing amplifier ] task performed by a [proc-amp] for short.

Digital Noise Reduction (DNR) is both cheaper and considered more precise than analog noise reduction which can have non-linear characteristics (which are difficult to describe and teach how to use). Non-linear noise reduction is harder to repair or reproduce in similar or duplicate circuits.

Not all VHS players have NR or DNR circuits, as its considered a more expensive and premium feature.

Another way to improve VHS playback is to tune the tracking and control circuits based on the type of tape inserted into the system.

Mitsubishi pioneered a technique called "Perfect Tape" or "Twin Perfect".

Originally intended for "preparing" the VHS recorder function, it "samples" any tape inserted into the VHS recorder/player which does not have its write-protect tab broken off.. in anticipation that it may be used for making a new recording. By doing this it can configure or optimize various circuits in the VHS player to make the best use of the Tape provided and make the strongest recording possible. On playback it similarly is optimized to extract the best signal possible.

The on screen display for a Mitsubishi VHS player with this feature can be used to manually engage or disengage this feature on demand regardless of the state of the write-protect tab.

Mitsubishi VHS players also have a direct drive method of fast forward or fast rewind called "Turbo Drive" which was used to reduce the time a consumer was required to wait for a Tape to be wound or rewound for return to a rental store.