Video Tuning

Before capturing video, it is necessary to adjust the settings of your video capture device.  This means that you must alter the brightness, contrast, color, and hue settings so that your video looks the way it's supposed to look.  This process is made difficult by the fact that each computer monitor will display a video in a slightly different fashion.  To work around this problem, we will use a tool called a histogram that is found in VirtualDub.

This portion of the guide is based on the assumption that you are using a WinTV capture card.  However, it's no problem if you are using another capture device.  Every device should have a similar settings panel that allows you to adjust the brightness, contrast, saturation (color), and hue of the image.

1)  Initial Video Tuning

Before we use the histogram to fine tune the image settings for your capture device, you can do a pretty good job of adjusting it by yourself.  First connect your video source (e.g. VCR) to the capture card in your computer.  Then run VirtualDub and click on File -> Capture AVI to enter the video capture mode.   

Once you are in capture mode, click on Video -> Overlay to enable the display of the input video.  If you press Play on your VCR, the image should appear on the screen.  If it doesn't, recheck your cable connections.

Now go to Video -> Source and begin adjusting the color/contrast/etc. settings.  Play with the settings until you have an image that looks "good".  By "good" I mean not too dark, not too bright, having bright colors, etc.  Here is an overview of what the settings will do:

As an example, here is a picture of the settings I ordinarily use with my WinTV-GO card:

When you are satisfied that the image looks "good", move on to the next step.

2)  Fine Tune the Video With the Histogram

Now we get to see how close you came to the correct video settings.  To begin, click on Video -> Preview w/ histogram.  If you are lucky, a graph will pop up below your video.  If a black and white graph does not appear, you can click on Video -> Histogram to use an alternate histogram.  However, if at all possible, use the Preview w/ histogram option.  You should now see something similar to this:

Don't be afraid of the histogram; it's simpler than it looks.  Basically, the graph represents the entire spectrum of colors, with pure black being on the far left and pure white being on the far right.  Your goal will be to center the histogram so that graph (the white part) just barely fits from end to end of the graph window.  By doing this, you ensure that the darkest color in your image is a pure black and the lightest color in the image is a pure white.

Below, after a not-so-brief explanation of histograms, you will find instructions on how to adjust your video settings to create a correct histogram.

A)  Sample Histogram Explanations

To obtain a useful histogram, it is necessary to find a scene that has a mostly even amount of pure black and pure white objects in the scene.  (It's okay if there are colored objects in there too, but you need to have the black and white stuff.)  When you have found such a frame, you will pause your video device (VCR).  The histogram should then stay relatively constant, allowing you to adjust the image.  You can click on Video -> Source to adjust the histogram.  (Please note that if the Preview w/ histogram option does not work for you and you are forced to use the Video -> Histogram option, you will have to close the histogram window before VirtualDub allows you to alter the settings in the Video -> Source panel.  You can then re-open the histogram window to see if your changes to the settings had a positive effect.)

Here are some pictures of histograms, what they mean, and how to correct them:

If the left end of your graph don't reach the end of the graph window, that means that your image has the brightness set incorrectly.  In the above picture, the brightness is set too high.  To fix this problem, decrease the brightness in the Video -> Source control panel.

Look on the very right side of the graph and notice how the white portion is much higher than the rest of the graph.  Whenever you see this type of build-up, it means that there is too much white or black in an image.  In this picture, since the build-up is on the right side, the image has too much white.  To solve this, decrease the contrast.

Notice that the graph pretty much drops off on the right side of the graph window.  This means that there is not enough white in the image.  To correct this, increase the contrast.

This is what your final histogram should look like.  Notice that the graph reaches both ends of the graph windows, but there is no build-up on either end.

B)  Effects of Changing Your Video Settings

Here is a summary of how certain settings alter the graph:

C)  Creating the Correct Histogram

Written below is a method for creating a correct histogram.  This method works well with my WinTV card.  However, there are a few things you should know before attempting to create a correct histogram.

Note #1:  Most VCRs will come out of pause mode after few minutes.  If this happens, try your best to pause it again at the same point in the video.   

Note #2:  Remember that if the Preview w/ histogram option does not work for you and you are forced to use the Video -> Histogram option, you will have to close the histogram window before VirtualDub allows you to alter the settings in the Video -> Source panel.  You can then re-open the histogram window to see if your new settings produced the desired effect. 

Note #3:  If you are forced to use the Video -> Histogram option, it is possible that upon re-opening the histogram window you will find that the graph has disappeared.  This can happen if your capture device doesn't properly update the display during a paused image.  To correct this, you can either:

A)  Disconnect and reconnect your video cable.
B)  Rewind your VCR a few seconds, hit play, and then pause it at the same place you had it paused before.

1)  To begin, find a scene with equal amounts of pure black and pure white and pause the VCR there.

2)  Greatly decrease the contrast so that you can see where the graph drops off on the right end:

3)  Increase the brightness until you can see where the graph drops off on both ends:

4)  Move the left side of the graph so that it just barely touches the very left side of the graph window.  You can do this by decreasing the brightness:

5)  Increase the contrast until the right side of the graph just barely touches the right side of the graph window:

6)  Verify that the graph is still properly positioned at the left edge of the graph window.  If it isn't, slightly increase the brightness while decreasing the contrast until the graph is properly centered:

7)  Finally, press play on the VCR.  If the scene you chose was a good one, the histogram will stay properly centered during future scenes with black and white.  However, if you see the graph dropping off on the right side even when there is white on the screen, that means you should increase the contrast a bit more.  Having a little too much contrast is better than not having enough:

If you correctly completed the above steps, the brightness of your image should look very good.  If the image doesn't look right, try repeating the process.

3)  Adjust the Saturation (Color)

Fortunately, setting the saturation much easier than adjusting the brightness/contrast.  Here is my preferred method of setting a good saturation (color) level:

1)  Find a scene in the video where there is a bright, deep red color.  Now pause the VCR there.

2)  Increase the saturation (color) in the Video -> Source panel until the red starts to look too bright.  By "too bright" I mean that it will look like the red is glowing, as if it were fiery hot.

3)  Decrease the saturation until the red color looks natural again.

4)  Decrease the saturation a little bit more to assure that no other red object in your video will be too bright.

Here are a few examples of poorly and properly configured saturation levels:

Too little saturation:  the colors are very dull.

Too much saturation:  the image is almost glowing.

Correct level of saturation:  everything looks normal.

If you were able to do everything in this section of the guide, you have completed the video tuning process.  

In the future, you should  not have to go this this entire process again.  Usually, all you have to do is make sure that the image looks bright enough.  If you find that a certain video looks dark, just increase the contrast by a small amount.  Conversely, if a certain video looks too bright, lower the contrast a little bit.
Also, it is possible (but less likely) that the saturation (color) might change.  If the colors look too dull, increase the saturation (color).  If they look too bright (i.e. almost glowing), decrease the saturation (color).

Now head on over to the Audio Tuning section.