The Lyric Convolver filter is a utility effect that gives access to the 3x3 image convolver within Final Cut. Convolution is a fundamental image-processing operation used for tasks such as image bluring, edge-detection, embossing, and so on.
It can be seen as a kind of local averaging operation: each pixel in the output image is modified based on the values of it's neighboring pixels. In Final Cut's case, this neighborhood is the 3x3 square of pixels centered on the current pixel. To perform a convolution, you specify a 3x3 array of numbers, one for each of the neighborhood pixels and the current center pixel, and these numbers specify how much the corresponding pixel contributes to the output current pixel. This array is called a Convolution Kernel. The Lyric Convolver filter let's you specify the numbers in a kernel and will apply a convolution based on this kernel to produce the output video image. It also supplies a number of preset kernels that do common processing tasks.
There is a reasonably non-technical introduction to image convolution on the Florida State University's Optical Microscopy site.
The Lyric Convolver filter includes a set of effect controls that are common across all Lyric effect filters. For a detailed description of these controls, please see the Common Effect Controls documentation.
Additionally, all Lyric Effect filters can be applied through mattes or masks to constrain the filter effect to particular areas of the image. For background information on mattes and masks, please refer to the Lyric Matte Primer.
The Kernel dropdown menu lets you select from one of the preset kernels or indicate that you wish to supply a custom kernel with the following sliders by selecting Custom Kernel.
The preset entries in the Kernel menu show the numbers in their kernels in row-order, which is the same order for the following sliders.
The Custom Kernel section has a slider for each position in the 3 x 3 array. The entries in the array are numbered [0,0] for the top left down to [2,2] for the bottom right, with [1,1] for the current center pixel.
The convolution is applied by multiplying the pixels values under the kernel by the corresponding kernel cell value and summing the results. Frequently, this results in an output pixel value that exceeds the value for pure white, so usually the result is divided by some given value, called the convolution Divisor, and possibly offset by another value called the convolution Bias. The Lyric Convolver can estimate a divisor and bias for a given kernel and will do so if you check the Auto Normalize checkbox. If you disable this, you can supply your own divisor and bias and it is recommended that you experiment with different divisors and biases as you work with different kernels.
The Effect Controls section is a set of common controls that are documented on the Common Effect Controls page. They can be used to achieve masked and other specialized filter effects.
= Edge North
= Laplacian 8
= Negative Blur