15 Rendered effects (intro)
Another type of effect is performed on a section of the track and the result stored somewhere before it is played back. The result is usually pasted into the track to replace the original data.
In 15 years, the only effect we actually ever rendered with this feature was normalize. We’ve never rendered an effect which could be applied on the timeline, even though this feature supports rendering realtime effects. This feature was implemented back when computers were too slow to play back anything in realtime. Decent sounding reverb took a long time & was considered major number crunching.
The rendered effects are not listed in the resource window but instead are accessed through the Audio->Render effect and Video->Render effect menu options. Each of these menu options brings up a dialog for the rendered effect. Rendered effects apply to only one type of track, either audio or video. If no tracks of the type exist, an error pops up.
A region of the timeline to apply the effect to must be defined before selecting Render effect…. If no in/out points and no highlighted region exist, the entire region after the insertion point is treated as the affected region. Otherwise, the region between the in/out points or the highlighted region is the affected region.
Secondly, the tracks to apply the rendered affect to need to be armed. All other tracks are ignored.
Finally, the rendered affect processes certain track attributes when it reads its input data but not others. Transitions in the affected track are applied. Nudge is not and effects are not. This allows the new data to be pasted into the existing position without changing the nudge value.
In the render effect dialog is a list of all the realtime and all the rendered effects. The difference here is that the realtime effects are rendered to disk and not applied under the track. Highlight an effect in the list to designate it as the one being performed.
Define a file to render the effect to in the Select a file to render to box.
magnifying glass allows file selection from a list.Select a file format which can handle the track type. 
wrench allows configuration specific to the file format.
There is also an option for creating a new file at each label. If you have a CD rip on the timeline which you want to divide into different files, the labels would become dividing points between the files if this option were selected. When the timeline is divided by labels, the effect is re-initialized at every label. Normalize operations take the peak in the current file and not in the entire timeline.
Finally there is an insertion strategy just like in the render dialog. It should be noted that even though the effect applies only to audio or video, the insertion strategy applies to all tracks just like a clipboard operation.
When you click OK in the effect dialog, it calls the GUI of the effect. If the effect is also a realtime effect, a second GUI appears to prompt for acceptance or rejection of the current settings. After accepting the settings, the effect is processed.15.1 Rendered audio effects
15.1.1 Resample
How to reduce the dynamic range of audio.
For smaller changes in duration, in the range of 5%, Resample should be used. This changes the pitch of the audio but small enough changes aren't noticable. Resample doesn't introduce any windowing artifacts, so this is most useful for slight duration changes where the listener isn't supposed to know what's going on.
This multiplies the number of each output sample by a scale factor to arrive at the number of the input sample. The output file’s sample rate is set to the project sample rate but its length is changed to reflect the scaled number of samples. It also filters the resampled audio to remove aliasing.
If the scale factor is 2, every 2 input samples will be reduced to 1 output sample and the output file will have half as many samples as the input sequence. If it is 0.5, every 0.5 input samples will be stretched to 1 output sample and the output file will have twice as many samples as the input sequence.15.1.2 CD Ripper
Extract audio from CD.
It allows you to extract the entire CD as well as only part of the CD or of the track. You need to select the range to transfer: from 'Track №', 'Min', 'Sec' to 'Track №', 'Min', 'Sec'.
Note: The plugin accepts ending tracks higher than the total tracks. Put in 100 for the ending track to get the entire disk. The plugin rips all tracks of the range to a single audio file.
15.2 Rendered video effects
15.2.1 Reframe
This does exactly the same thing as ReframeRT in Stretch mode. It multiplies the output frame number by the scale factor to arrive at the input frame number and changes the length of the sequence. Unlike ReframeRT, this must run from the Video menu and render its output.
Be aware Reframe does not write the scaled frame rate as the frame rate of the rendered file. It produces a file of scaled length and equal frame rate as the project. The new length is 1/scale factor as big as the original sequence.
To create a slow-motion of fast moving video:
- Select the video clip you wish to re-frame and put it on a video track
- Select the area you wish to reframe
- From the Video menu, select the Render Effect option
- From the effect list, select Reframe
- Enter the output format and insertion strategy for the new clip to be created
- Press Ok
- At the popup menu, enter the scale factor 2 to run twice as fast, and .5 to run at half speed
15.2.2 GreyCStoration
How to perform advanced denoising and restoration.
GREYCstoration is an image regularization algorithm which is able to process a color image by locally removing small variations of pixel intensities while preserving significant global image features, such as edges and corners. The most direct application of image regularization is image denoising.
GREYCstoration is based on state-of-the-art image processing methods using nonlinear multi-valued diffusion PDE (Partial Differential Equations). This kind of method generally outperforms basic image filtering techniques (such as convolution, median filtering, etc.), classically encountered in image painting programs.
GREYCstoration is a rendered plugin, but it can be optionally used as a realtime effect. It is important to note, however, that as a realtime effect, GreyCStoration is very slow.
Parameters:
- Amplitude (dt):
This parameter represents the average amount of smoothing that is performed. GREYCstoration performs a spatial averaging of pixel values, and Amplitude represents a kind of dimension of the area where the smoothing is computed. It is related to the PDE time step. Default value is 40. Prefer using a larger value than using multiple iterations when possible (at least until undesirable artifacts appear), it will speed up the whole process.
- Sharpness (p):
This parameter tells GREYCstoration about structure preservation. Once the local structures of the image have been detected, GREYCstoration has to decide how much he will smooth image pixels. Basically, it decreases the smoothing when the local structure is contrasted. The Sharpness parameter simply tells how this decreasing must be considered. When Sharpness is high, even low-contrasted structures will be preserved. Do not set Sharpness too high or the noise may be preserved. On the contrary, when Sharpness is low, the structures have to be very contrasted to avoid local smoothing. Do not set p too low or existing image structures will be over-smoothed. As you can see, there is a (sometimes difficult) trade-off to find when setting this parameter. Default value is 0.8 and typical values range from 0 to 5.
- Anisotropy (a):
This parameters set the anisotropy level of the considered smoothing. It ranges from 0 (which means ’purely isotropic’) to 1 (which means ’purely anisotropic’). The anisotropy notion relates to the way the performed smoothing orientation will extend locally in space : a purely isotropic smoothing (0) will be performed in all possible directions, while a purely anisotropic smoothing (1) will be performed only along the directions of the structures. Values of anisotropy between 0 and 1 tell GREYCstoration to smooth the image mainly along the structure directions, but with a certain percentage of tolerance. Default value for a if 0.8 (which is already very anisotropic).
- Noise scale (alpha):
This parameter is mathematically defined as the standard deviation of a blurring gaussian kernel applied to the original image before estimating its geometry. In other words, it defines a kind of scale under which details won’t be considered as structures but much more as noise. This parameter highly depends on the level of noise present on your image. Remember that increasing too much this parameter will tell GREYCstoration to smooth more structures. It can be useful for special visual effects though. Default value of alpha is 0.8, which is relatively low (many details should be preserved). Note how the details are ignored for high values of alpha.
More details on the GreyCStoration functionality can be found here: Demonstration, User's Guide.
Nota bene: GREYCstoration is not maintained anymore. Greycstoration project has been recently integrated in G'mic project (a new plug-in for GIMP). This is a complete image processing toolbox which contains all the GREYCstoration features (of course), but also much much more filters for image denoising, enhancement, applying artistic effects and so on… However, G'mic does not provide any versions usable with cinelerra, and contains much unusefull features for videos softwares.