Video Blending Matrix

Wide bandwidth DC signal processing, summing and full wave rectification, triple colorspace (RGB) mixing, voltage-controlled solarization

Video Blending Matrix is a versatile signal processor which sums input signals in various mathematical input and output modes. Three signal mixers can either be used independently or combined in various matrix configurations.

MIXER INPUTS
Each mixer has five signal inputs, four of which have associated voltage processing controls. With level and inversion controls, and the inversion mode switch, three variable input functions are possible: addition, subtraction, and inverse addition. With no signal input, each control can function as a variable 1 Volt bias control.

MIXER OUTPUTS
Two separate outputs are available for each mixer. The sum output is the sum of all input signals. The absolute output is the absolute value of the sum — that is, negative signals are inverted and become positive.

SOFT LIMITERS
Each channel has a dual soft limiter on its output. The limiter compresses the signal starting at 1 Volt for the positive limiter and -1 Volt for the negative limiter. This assists in pushing signal excursions above 1 Volt back down into viewable range, and results in more dynamic mixer feedback patches.

PATCHING TECHNIQUES
Addition
Insert a signal to any A, B, C or D mix input. Turn the associated level control clockwise from the center position to add this signal to the corresponding mix outputs.

Subtraction
Insert a signal to any A, B, C or D mix input. Flip the associated inversion mode toggle switch to -n position. Turn the associated level control counter-clockwise from the center position to subtract this signal from the corresponding mix outputs.

Inversion
Insert a signal to any A, B, C or D mix input. Flip the associated inversion mode toggle switch to 1-n position. Turn the associated level control counter-clockwise from the center position to invert and add this signal to the corresponding mix outputs.

1V Bias
Any input/level control can be used as a static 1 Volt bias control. Flip the associated inversion mode toggle switch to 1-n position. Turn the knob from center to counter-clockwise to add a variable 1 Volt bias to the corresponding mix outputs.

Solarization (full wave rectification)
Use the techniques described above to fully subtract the signal to be solarized from the mix, and then apply a variable 1V Bias using an unused input of the same mix. Monitor the mix at the ABS output.

RGB Matrix
Feed the outputs of all 3 mixers to Red, Green & Blue inputs of the Color Video Encoder. Insert signal to be colorized to A1, B1, C1, or D1 inputs. Cascaded jacks pass the signal to the two jacks below it, allowing separate Red, Green & Blue inputs for the single input signal.

Chained Operations
Using the direct signal inputs on the left side of the module, multiple Video Blending Matrix modules can be chained together for seamless operation into a giant Matrix Mixer. Additionally, the outputs of channels within VBM can be chained to the direct inputs to enable use as a giant single channel mixer with up to 13 inputs (2 channels’ direct inputs will be used by the chaining patch.) When patching in this manner, it is usually most intuitive to work from bottom (channel 3) to top (channel 1), so that switched jack connections are broken as signals are inserted to the mix. Dummy plugs (a patch cable disconnected on one end) can be inserted to break switched connections of any unused inputs.

Mixer Feedback
By taking an output of the mixer, processing it further, and feeding it back into a mixer input (or to the control input of a signal generator that is feeding the mix), complex and often unexpected video feedback can result. Experiment with both Sum and Absolute outputs and various inversion modes on the feedback input.