When encoding your favourite DVD’s or BluRays, one of the issues you’re bound to run into at some point is a noisy source.
Now I’m using the term “noise” very loosely here – when I say “noise”, I’m basically referring to little dots on the screen that aren’t part of the actual picture. This can be the result of film grain, compression artifacts, a poor camera, etc. Before I start to sound like I’m trying to get everyone on the “noise is evil” bandwagon, note that sometimes film grain is digitally added to a movie during production to go for a certain look. In less common cases, digital film grain can be added to cover up other issues such as color banding in the master. Whether noise is good or bad often depends on it’s intent, and also depends on your own preferences – some people like it, others loath it.
That said, when it comes to the video encoder, noise is extra detail – detail that the encoder is going to try and keep, at least to some extent. And this is expensive detail to keep. Encoding a noisy source can easily double the bit-rate/file-size necessary at a given quality. And if you don’t give a noisy source enough bitrate, the overall quality of the picture tends to suffer heavily.
If you’re looking for small file sizes, or you’re not a fan of noise on a visual level, removing some of this noise can be helpful. Handbrake includes a denoiser, so here I’ll show you how to use it.
Handbrake uses a denoiser called “HQDN3D”. It’s not the best or most powerful denoiser out there, but it’s fairly quick and does a reasonable job as long as your source wasn’t a disaster and/or your expectations aren’t crazy.
It’s accessed in the “Picture Settings” section of Handbrake.
The default settings are:
At some point you probably want to see what denoising actually does, so in the video below, I start by showing the effects of Weak/Medium/Strong before delving into the custom settings. I suggest you tinker with the buttons in the player to set this to 1080p and fullscreen (if your connection can’t handle 1080p, go as high as you can – otherwise you’ll have to rely on the pictures below, as lower resolutions on YouTube kill too much detail).
If you’re planning to de-noise, but are not interested in the Custom stuff and just want to use the presets, my suggestion is to start at “Weak”, because you start to get significant blur as you move towards “Medium” and “Strong”.
CUSTOM DENOISE SETTINGS
If you’re remotely serious about denoising, custom settings are the way to go.
Custom values are entered in the form of 0:0:0:0 . Using all zeroes would not do any denoising, so realistically you’d put some actual numbers in there. But before you start plunking in random numbers, to give you a little bit of a reference, here are what those presets above actually use:
Handbrake’s denoiser does 2 types of denoising. One is called “spacial” which is represented by the first 2 numbers. The other is called “temporal” which is represented by the last 2 numbers. We’ll look at both.
The first 2 numbers have to do with “spacial” denoising. For example, 2:2:0:0 would only do spacial denoising.
The technical jargon has to do with looking at a single frame. To put it in an easy-to-understand way, the end effect is that the picture is softened, smoothed, or blurred (pick your favourite term). The noise is caught in the process, and softened/smoothed/blurred away.
I’ve used high spacial denoising below (higher than a rational person would normally use) to show what happens as this setting is pushed too far. Click for a larger image.
You can easily see the effects continue reading…