I first tried using the GPU, using old school GPGPU textures and OpenGL ES 2.0 shaders, but unfortunately the performance wasn't there for a variety of reasons given in [1].
SnappyCam has since been making extensive use of ARM NEON for the JPEG codec and a bunch of other image signal processing operations, like digital zoom. It's a great instruction set!
Just curious, I know nothing about low level ARM stuff. I was wondering is this iPhone/Apple specific tech or is the work you've done portable to other mobile platforms? Congrats on what you've done. I couldn't quite work out whether you've optimized the hell out of the standard DCT algorithms or whether you've come up with new algorithms. If it's the latter would you be able to publish them or would that give away too much secret sauce? ;-)
No, NEON is an ARM-specific tech, and is widely available and used e.g. on Android smartphones.
It's like MMX / SSE of x86 world, a set of extra instructions to process many small integers in parallel in one instruction. Since image data are usually independent 3-byte pixels (or 3 planes of 1-byte subpixels, one per color channel), NEON is great for many image-processing tasks.
