View Full Version : Adjusting the color phase on a YUV source

03-09-2003, 11:13 PM
Hi there!

A while back on the old board I asked if it is possible to adjust the actual color phase angle of a YUV source. At the time I *was* given an answer, but I was horrifically distracted by life and an unhappy Toaster, and therefore not able to refine my question further.

You see, I must use the Pro ProcAmp skin for YUV, and while there is a "Hue" knob, it doesn't do anything (as I was told...). Someone told me (Paul...?) the way to adjust the hue in YUV is with the U and V offset and gain controls in the above skin.

But, If my camera ( or the dang agency tape) is outta whack, then the phase "angle" is all messed up, and *no* possible amount of offsetting or gaining is going to correct it. Think of the vectorscope...I want to "rotate" the color info, not move it up/down/left/right, or turn up/down the U or V info.

What am I overlooking?

Thanks for letting me dip into the well of experience...


03-10-2003, 09:03 AM
There actually *is* a question in the previous post... :)

03-10-2003, 11:53 AM

This has been a problem all along (and not limited to the Toaster).
If you're running in component, there is no hue adjustment to rotate the color on the vectorscope. You will get it if you are working with y/c.

We also have a pinnacle DV2000 system (which uses Premiere for editing, capturing & procamp setting) and get the same limitations.

Not being a formally educated vid engineer, I have no logical explaination or reasoning for this.


03-10-2003, 01:22 PM
Well. :(

Thanks for the reply. I found it odd that a moderator didn't answer.

So, I guess the next question is...is there a workaround? I certainly hope so.


03-10-2003, 05:53 PM
(as I said earlier, I'm not a video engineer, but this may help.

From what I understand, with a y/c (S-video) signal you have split chrominance and luminance. When you adjust hue, you are rotating the chrominance.

This changes with a component signal, which has it's components broken down in a different way. Something like the computer's RGB signal, but in an analog way. Y is Luminance.
R = R-Y (or V), G = Y, B = B-Y (or U).

Now, with this in mind it may be easier to see that you can change the phasing (hue) of one (chrominance) signal. But with the signal broken down into 3 separate components, you are limited to gain and offset adjustments, along with brightness and contrast. And this is not necessarily a shortcoming in the Toaster, but is a limitation of the component signal.

check this link for a better explaination than I gave.



03-10-2003, 10:58 PM
While it is true that analog component typically can not be hue adjusted at the source (BVW deck for instance), digital component can be and is on every digital vtr (DVW for instance) I have ever used. We are working with a digital signal inside of Toaster are we not? Additionally, post-production equipment has always been available to make hue as well as many other adjustments available to the analog component signal in the form of Color Correctors and Frame Sync's (and with some TBC's and Proc Amp's). This functionality should be available in the Toaster as well, IMO.

One trick that I have been using for years as an editor is to mix very slightly a heavily saturated background of the color that seems to be missing. This works very well with poorly color-balanced camera footage. It is somewhat less effective if all you need is a hue change but can work well in many cases. There are supplied tinting filters for TED that effectively can do exactly this. Also in Aura you could use this technique and selectively apply it to the whites, mids, or blacks through the judicious use of the stencil and the keyers.

03-11-2003, 03:55 PM
Actually, NO, you are not using the proc amp on digital inside of Toaster, you are using the proc amp to control circuits on the ANALOG hardware on the Toaster card.

This is why the proc amp will NOT work on a digital signal coming into the Toaster.

As for the color correction inside of TEd, that's different. In there, it should be possible to simulate a hue control for any signal, cause at that point it is digital.