This is a FIR filter with NEON speedup. The NEON version has been tested
for accuracy against the scalar one, and there is simple benchmarking
code in place as well.
Extremely highly optimized implementations of the ladder filter in Neon
assembler. The audio loops (both linear and non-linear) are hooked up
and running, while the matrix generation is still running in scalar
code, though the Neon version has been tested and benchmarked.
Performance numbers on Nexus 10: linear audio loop = 22.5 cycles.
Nonlinear audio loop = 62 cycles. Matrix generation = 580 cycles.
Note that the current code will crash on ARM v7 devices without Neon
(for example, Motorola Xoom).
This patch wires up the LFO to the synth unit, and makes it affect pitch
(control over amplitude is not there yet). It also adds LFO delay to the
base LFO implementation, and there are some other cleanups as well (for
example, not unpacking patch data every note).
LFO speeds, delays, and pitch modulation ranges have been calibrated
against the DX7, but testing hasn't been exhaustive.
A small amount of stats analysis, mostly max callback time, with simple
display in the UI.
Also improves pow calculation to use lut implementation instead of
math.h pow(), for a speedup somewhere around 20-30%.
The FM kernel yields itself well to speedup using NEON assembler. This
patch contains the NEON assembly code, plus C integration code
(including making sure that buffers are aligned to 16 bytes).
Raph Levien