CHV-electronics

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Noise Reduction V1.0

Get rid of noise and dust. Period!

It's as easy as it can be. Even though Noise Reduction is a very powerful tool, it only has four controls.

How does it work?
Noise Reduction is different to all the others de-noise tools out there. Most other tools simply apply a frame by frame blur over the video. And even if those tools omit edges, they will still just blur the video. If you want to get the noise back, you only have to apply a sharpen filter and your video is full of noise again. Noise Reduction works different, as it takes a completely different approach. Noise Reduction scans a certain timespan, compares all the frames of that timespan and evaluates mathematically what part of the video is real content and what part is noise that needs to be eliminated. By going that way you can get way better results as you have ever seen with Final Cut Pro.

There are only four controls:

Noise (to eliminate)
Here you can set the maximum amount of noise you want Noise Reduction to eliminate. Note: Don't set this control too high. You might also eliminate content that should stay in your video.

An example:

To demonstrate how the Noise parameter works, we choose a really bad video for this example. In the background you can see some cable cars. To the left you can see the tower of a crane.
A simple blur filter would have to give up on this one. Not Noise Reduction! Let's set Noise to 15. You can see that the noise is nearly gone, but the content of the video is still there. You can clearly see the cable-cars and the tower. Even the cables of the cable cars are now visible.
Let's set Noise to 50. What happens now? Noise Reduction now also tries to eliminate the "noise" it can see in the moving cable cars and (due to the moving camera) the moving crane tower. In this case a value of 50 would be a little too much as it also eliminates the content of the video.

What we learn from this example is, that you have to be careful with the Noise value. Too high values can destroy the footage, too low values have no effect. Values from 2 to 20 are good in most cases depending on the video and the amount of noise. Higher values reduce more noise, but also might eliminate content of the video. If the value is set too low, you will still see your noise. Suggestion: Play with this slider. Noise Reduction always shows you the final rendered video in the canvas. Begin with lower values and evaluate the best setting.

Used Timespan
This slider tells Noise Reduction how much video should be taken into account for the detection of the noise. A longer timespan looks at more surrounding frames, but might also add a little motion-blur effect. Good values go from 10 to 40.

Sensitivity
This is a very special control. Noise Reduction works, because it takes surrounding frames into account for the evaluation of the existing noise. If the current scene of your video changes (i.e. due to a cut), it is not useful for Noise Reduction to use these frames for the evaluation. Therefore Noise Reduction calculates a value that describes the difference between the single frames. The higher the value, the more likely it is that the scene has changed. This is what Sensitivity is for. This slider determines a threshold and tells Noise Reduction the maximum allowed amount of the difference between the frames. You don't need to cut you footage into little scenes. Noise Reduction takes care of scene changes automatically and makes it possible to eliminate the noise of a whole film at once.

If you check the Calc and show checkbox, you will see this additional info in the canvas:


The black marker in the center marks the current frame. The white surrounding dots represent the surrounding frames. A white dot means that the frame is taken into account for the noise evaluation. A red dot means that the frame will not be used.


The Sensitivity value to the right is the calculated difference between the current frame and the next frame.



Here we can see some frames that are marked in red color. These frames will not be used for the noise evaluation, as they are too different from the current frame anyway.



Here we can see a typical scene change. The Sensitivity value for this frame to the next frame is 15. This means that there did not change a lot between those two frames. But there is a big change to some earlier frames. This is a typical display after a scene change.


Hint: Remember that the noise will also show up in the Sensitivity value as it boosts up the value by the amount of the current noise. Even if you have a completely static scene, you will see that the Sensitivity value is not at zero. The value you see at that frame represents the actual noise and can be used to determine a good value for the Noise (to eliminate) slider.

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