Another reason to use good JVC VCRs - comb filters.

[Philbiker]

I recently have begun the process of transfering some of my LaserDisc and VHS to DVD using my computer. I'm no novice, I've been doing this for at least a year with my DV camcorder, with much success. Using an ADS Pyro I transferred some VHS successfully, but was curious about LaserDisc. I have read here about all the reasons to use the higher end JVC VCRs, and have owned an HR-S7600U for years. One of the reasons I bought the 7600, other than the great Time Base Correction and video processing, was in order to get a top notch 3-D comb filter.

The Comb Filter is perhaps the single most important piece of video hardware in the chain when using a composite source like LaserDisc and VHS. It is a little piece of electronics that separates the color from the black-and white sections of the picture that are combined in the composite cable. All other things being equal, a bad comb filter will always result in a poor picture.

I hooked my LaserDisc Player, a Pioneer CLD-D704, into the Pyro using composite video and started capturing from my LaserDiscs. I noticed a little rainbowing on a couple of still frames, so I decided to test the comb filter in this thing.

In order to see what was the best way to transfer my video, I pulled out my CAV LaserDisc of "Video Essentials" and ran the Snell & Wilcox test pattern in the "Video Test Patterns" section. here are the results...

Composite into the ADS Pyro A/V Link

The colors you're seeing here are an indication that the comb filter in the ADS Pyro A/V Link is most definitely not a 3-D unit.

S-Video from the CLD-D704

The CLD-D704 has a relatively good 2-D comb filter.

S-Video from the JVC HR-S7600U

The HR-S7600U has a quite good (for the day it was made) 3-D comb filter on board. The picture is not quite as good as I used to get from my CLD-99, but it's certinaly worth using for this kind of capture!

The video is more dramatic than the captures. I don't know if posting the Snell & Wilcox test pattern is a violation of any copyright, but feel free to delete this if you think it is.

I don't know how many people will even be able to use this tip, but I've gotten enough great usable information from this board that I figured I should give back when I discovered this.

[Epicurus8a]

Lordsmurf will probably love this.

[lordsmurf]

This is something gshelley and I have mentioned in the past, but it is nice to see it with some comparison images.

[gshelley61]

This is why I maintain the composite signal out of my CLD-D704 through my video processors and then let my JVC DVD recorder do the Y/C splitting. It has an excellent 3D motion adaptive filter that is far superior to the comb filter in the LD player.

[Megahurts]

Philbiker

Good comparision of comb filters.

But if you have a S-Video output as a laser disk player has and a S-Video input for your ADS Pyro, why yould need any comb filter? S-Video is superior to any comb filter.

Just curious,

Chas

[gshelley61]

Philbiker

Good comparision of comb filters.

But if you have a S-Video output as a laser disk player has and a S-Video input for your ADS Pyro, why yould need any comb filter? S-Video is superior to any comb filter.

Just curious,

Chas

Laserdisc is a native composite analog video source. A comb filter must therefore be used to separate the luma and chroma (Y and C) and create the s-video signal. The quality of the s-video signal from any laserdisc player is totally dependent on how well the comb filter splits the luma and chroma. Modern digital comb filters do a much better job of this than what you would find in a 10 year old laserdisc player.

S-video is simply a standard video signal with the luma and chroma information physically separated, while composite video carries both the luma and chroma combined in one signal. Laserdisc, broadcast TV, analog cable... they are all native composite signals. Your TV has a comb filter that separates the luma and chroma to display the signal (so do most cable boxes). Most videotape and all digital video sources have separated luma and chroma to start with.

[barrybear]

The type of distortion that you identified can indeed be improved by good quolity comb filters but that is not the end of the story. In a PAL/NTSC signal the chroma information is contained within the luma information . In the case of pal this is at 4,43megs the luma signal is 5.5megs. The reason SVHS is beter is because the chroma and blackand white components are processed seperatly.
In a compasite signal from a pal source you will always have this herringbone pattern at frequencies of 4.43 megs ( the areas on the screen you have identified)

Barrybear

[Philbiker]

thanks gshelley61 for saving me typing time.

My CLD-99 used to have a better comb filter than the JVC VCR even.

[Philbiker]

This is why I maintain the composite signal out of my CLD-D704 through my video processors and then let my JVC DVD recorder do the Y/C splitting. It has an excellent 3D motion adaptive filter that is far superior to the comb filter in the LD player.

Yeah, after I did that I went down to my theater room to see what the picture would look like down there. The 704 is in my office and probably will be for many months, as I've got a lot of LDs to transfer, so I have a backup CLD-D406 there plugged composite into my Infocus X1. The Snell & Wilcox pattern looked great down there, comparable to the output from the JVC VCR. The X1 with its great video processing really makes the most of the LD format!

[Marvingj]

Awesome!!!!