S-Video input colour correction by hardware

[Starman*]

I capture stills and video from a satellite receiver via s-video. The capture card is an ATi AIW which has limited colour correction ability. Once recording has started, you cannot adjust tone. Being NTSC, the colour can vary between and during broadcasts. I can adjust still captures after but it's not so practical with recorded video.

I have a particular problem of greyscale and near-greyscale having a green tint. The rest of the picture is not so badly affected.

What I need is an inline piece of hardware with s-video in and out that can adjust colour tone, preferably with some sort of additional auto colour correction and some means of addressing the above green problem. Simple rgb adjustment will not do the job. Any suggestions?

Starman*

[redwudz]

Maybe something like a Sima SCC Video Color Corrector: http://www.bhphotovideo.com/bnh/controller/home?A=details&Q=&is=REG&O=productlist&sku=168992

Sima may have some other units that will do what you need also: http://www.simaproducts.com/products/product_results.php?category_id=22

And welcome to our forums.

[CCEncoder]

Why would this occurr if your equipment is not failing? Does anyone know the origen?

[Starman*]

Redwudz, that's better than I've found although it's difficult to say if correcting the greyscale/green can be done without biasing the rest of the pic too much. Definitely good for standard corrections. I came across their more expensive unit some time ago (just too much money) but never found the cheaper unit you linked to.

CCEncoder, hello, it's NTSC!! I've had both cable and satellite. The variations in tone have got better over the years but are still present. To give you some idea of how bad it was 5 years ago, attached is a reduced size image showing four of my stations, captured with the same settings within seconds of each other. Not nearly as bad nowadays.

Although it's not an issue here, average audio volumes between stations can vary about 20dB.

Thanks for the comments.

Starman*

[JohnnyMalaria]

It sounds like you may have a phase/tint/hue problem. To correct that post-capture, you need to work in the YCrCb color space - as you mentioned, RGB adjustment won't work.

This may be convoluted but - to see if phase/tint/hue is the problem, try this (assuming you have Windows XP...)

1. Convert the captured video to DV format (e.g., Movie Maker or Virtual Dub)
2. Run the DV file through our Enosoft DV Processor - it has a built-in proc amp that can let you adjust phase/tint/hue properly as well as white balance, brightness etc etc. The greenish cast you see on greys could be due to one of the two chroma components (Cr and Cb) being offset - you can tweak that, too!

This will at least let you determine what you need to do to the video signal if you still want a hardware solution and, for now at least, it's free (since it is beta).

Oh - and now you know why "NTSC" - Never The Same Color!

[CCEncoder]

therefore you mean we all need to buy this color corrector devices if we don't want to ignore it?

[edDV]

You have a bad cable company is what you have.

In the last 2 years my area has gone from early 70's awful 450Mhz (75 channel) patchwork to state cable art at 750 MHz HFC (hybrid fiber/coax). No hue shift problems any more. Black and white levels still vary +/- 1 IRE over the channels. If it gets further out than that I give them hell on the tech line.

To deal with the legacy you need a proc amp on the capture input or correct digially after capture (much processing). The cheap Sima boxes help a bit for hue but introduce other errors (mostly crosstalk and frequency response).

[CCEncoder]

You have a bad cable company is what you have.

In the last 2 years my area has gone from early 70's awful 450Mhz (75 channel) patchwork to state cable art at 750 MHz HFC (hybrid fiber/coax). No hue shift problems any more. Black and white levels still vary +/- 1 IRE over the channels. If it gets further out than that I give them hell on the tech line.

To deal with the legacy you need a proc amp on the capture input or correct digially after capture (much processing). The cheap Sima boxes help a bit for hue but introduce other errors (mostly crosstalk and frequency response).

So it depends on the company or the area?

[edDV]

So it depends on the company or the area?

The company in your local area. Their local infrastructure.

[Starman*]

EdDV, you're right, the cable company was terrible. I had snow all over the picture and 3 (apparently blind) techs told me the signal was fine. Had to get the supervisor in to get an admission it was their problem. That's why I went to satellite! For all their current failings they are still better than the cable guys.

JohnnyMalaria, I downloaded Enosoft a few weeks ago. The problem is that it only works for live video if you have a camera and test screen (like the plastic lid in their guide!). I really don't want to process the video afterwards. I could take a second look using DV as you suggested, to try to identify the correction needed, but that only works for that station and that show.

I mostly do still captures and would prefer to correct up front. For small errors I use a graphics editor. One of the apps I use for correcting radical errors is iCorrect EditLab. You use a picker to select multiple should-be-greyscale points on the image. It divides the greyscale spectrum into 5 and corrects differently for each.

My tv is much better at handling the colour, it has an autopilot which works quite well. No greyscale/green. However, it adds blue to some scenes so that red appears purple. My receiver is clearly not the best and I may have to wait until I upgrade to an HD receiver to see if I can get better colour control - not that HD is necessarily any better other than resolution.

Starman*

[JohnnyMalaria]

JohnnyMalaria, I downloaded Enosoft a few weeks ago. The problem is that it only works for live video if you have a camera and test screen (like the plastic lid in their guide!). I really don't want to process the video afterwards. I could take a second look using DV as you suggested, to try to identify the correction needed, but that only works for that station and that show.

Our guide (with the plastic lid!) is really geared for shooting video and getting the settings right. You don't have to have a test screen or have a camera to do the adjustment. You can open an existing DV format AVI file and simply adjust the Phase setting in the Proc Amp (same as Tint/Hue etc) until the video "looks right" - just as you would with stand-alone corrector or with the Phase/Tint/Hue control on a TV. If the colour correction needed for a given station is always the same, you can save the Proc Amp settings for each station.

Do you have a DV camcorder with "pass through" and a Firewire/IEEE 1394 port on your computer? If so, you can connect the S-Video output from your receiver to the camcorder and have the camcorder encode the video to DV, send it out the Firewire port and into your computer. That way, the DV Processor software will be able to work in real-time - it will correct the video and save the corrected version onto your hard drive. There will be no need for post-processing etc.

[Starman*]

The problem with DV is that for recorded video, I typically make a dvd. That means re-encoding if recorded in DV, which is time-consuming.

I don't have a DV camcorder so that's presently not an option. Not a bad suggeston though.

I may convert some mpeg2 video into DV to see how effective Enosoft is with my green/greyscale problem.

Thanks for the persistence!

Starman*