Re: [LAD] Linux-audio-dev Digest, Vol 44, Issue 6

On Wed, 2010-10-13 at 07:09 +0200, Stéphane Letz wrote: If we for now ignore getting data in and out - which I understand you are reading up upon now - there are two main use cases: a) Vertical signal flow: The signal flows from the top of each thread, starting at a location in shared memory chosen by indexing and ends up in another, fixed and known location, also in shared memory. Shared memory works like a switchboard with 4096 plugs, where any output can be the input of any other. In this case the code is identical to what you'll find in textbooks or floating around in DSP forums, including this one. The difference being that you'll get 128 instances of each functionality rather than just one. b) Horisontal signal flow: The above approach does not work for things like say delaylines (longer than a few samples) where you want each instance to have their delaytime individually parameterized. In this case you will therefore first transform the outputs so that a collection of vertical signals like: a A 1 $ a b c d.. b B 2 # A B C D.. c C 3 ! becomes horisontal: 1 2 3 4.. d D 4 ? $ # ! ?.. : : : : You will want to do this in chunks of 16 elements because this is how the memory controller works. A codepath driving 128 threads can then adress 8 unrelated global memory locations in parallel to store as well as load the right chunks(s) back into shared memory - after which the individual threads can look left and right for finetuning, interpolation and/or FIR filtering. -- eins, zwei, drei ... tekno tekno?? http://www.youtube.com/watch?v=ZEgbW1FxR78