This video demonstrates how you can do basic vocoding using Photoshop and Photosounder (an application for Windows & Mac that translates sounds to images and vice-versa):

• The carrier signal (a saw wave) and the modulator (HAL 9000’s voice) are turned into images using Photosounder.
• Then in Photoshop, the voice is vertically blurred as to fuse the different harmonics together, then it’s pasted on top of the image of the saw wave by multiplication.
• The result is then loaded into Photosounder in lossless mode with the sound of the carrier as a reference signal, giving the vocoded voice as a result.

Why use Photoshop as a vocoder?

This is an example of how Photosounder lets you use image-editing tools to look at sound design in a new way.

More details are available at the Photosounder site.

via Photosounder