Temporal noise reduction

- Temporal noise reduction works a little differently than the spatial noise reduction we just talked about. Spatial noise reduction is looking at a single frame, individually, and examining, looking for areas of noise, whereas temporal noise reduction takes the current frame and compares it to the surrounding frames, looks for where it thinks is noise, and then tries to kind of average them out or remove those areas to reduce the noise for us. Let's take a quick look at our options when we're using temporal noise reduction.

By default, it's turned off, because the number of frames is zero. Remember, temporal noise reduction is looking at the frames around the current frame, so we need to either select one or two in order to activate temporal noise reduction. When we do, these tools will become active. So I'll go ahead and I'll select one. Now, how do you decide whether you select one or two? Well, it's a combination of quality, speed, and what's actually going on on the image.

The higher the number, the more quality you'll get, the slower your playback performance, the longer your render times. The thing is, you also want to take a look at the image itself. Let me turn this off. So I'll set it to zero, and let's look at her again. And I'm going to play her through. And how much movement is there? There's a fair amount of movement, but it's not like NASCAR movement, right? It's not like high-speed-sports kind of movement, and so what happens is, if you go to two frames for analysis, if there's a lot of, really lots of motion blur going on in your image, going to two frames will actually kind of reduce the quality of your image, because it's going to see that motion blur as noise, and try to remove it, where you actually want to keep it.

In those cases, you want to set it to one. In other cases, like this, where there's very little movement, or you don't really have to worry about motion blur, then it's appropriate to kick it up to two. Now, we can further refine our algorithms, first by using the Motion Estimation Type. When we have Faster selected, it's, of course, quicker to render, quicker to play out, not quite as accurate as when we select Better. Better will introduce a big performance hit on playback, a big performance hit on rendering, but it's a lot better at finding motion blur and not trying to de-noise the motion blur.

Now, once we make this selection, we can then further refine that by saying, yeah, we've got huge amounts of motion happening in here by selecting Large, we've got some motion happening by selecting Medium, or there isn't much happening at all, all of this will help DaVinci Resolve refine its noise reduction. In this particular image, I would set it for Medium. Now, if I hit Play, let's take a look at what our playback speed is. And I'm still getting 23976. Why? Because, like spatial noise reduction, these settings tell the algorithm how to act, but until we actually set a threshold number, nothing's going to happen.

So we need to bring this number off of zero and start pulling it up. We can pull it all the way up to 100. If I go ahead and do that, and Motion is, again, another way of refining through DaVinci Resolve how much motion blur is in this image. The higher the number, the more motion blur will be removed. There isn't a lot in here, but I don't really think I need a high number. Let's go ahead-- Let's just kick these both up to 100, see what the heck happens. I'll hit Play, and (chuckles) yeah. Now we're back to that spatial noise reduction number of around three and a half frames per second.

That's when we go and kick on the Smart User Cache, and now it's going to render out our clip. All right, there we go, I'm going to go ahead and hit Play. And let's Shift+F, and yeah, we're getting full-time playback, and what kind of noise reduction am I seeing? And as I look, yeah, on her neck, yeah, right there, you can see there's not a lot of noise at all in there. This is definitely the way we wanted to go. Temporal noise reduction on this shot is way more effective than spatial noise reduction, and it really even looks better when I look on my reference monitor.

So I'm really happy. Now, I've pushed these settings really hard. I almost never take those settings and put them up at 100. It usually does more damage to the image than it does help the image, so I tend to avoid it. In the movie where I talk about noise reduction tips, I'll share with you kind of my favorite starting settings, where I begin my noise reduction, and then refine from there, and also talk about a couple of tips and tricks for if you have to go aggressive on your noise reduction. How can you do that without completely destroying the entire image?