This commit is a test implementation of a half-rate FIR structure
(basically a Toom-Cook). It's not bad in the scalar case, but the
benefit is marginal at best in NEON.
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.
The sawtest.py script generates audio samples for various filter
implementations (including matrix exponential and TPT) with various
input signals and settings. It should be useful for comparing the
quality of the various implementations, even though it's pretty slow.
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 implements nonlinear distortion in the resonant ladder
filter. It's based on the differential equations in the Huovilainen '04
DAFx paper, but using matrix exponential to compute the evolution of the
state variables. The implementation is scalar (and calls into sqrtf),
but designed to be implemented in very efficient SIMD.
This patch changes from the cascaded one pole filter approach to
a matrix based approach, computing the exponential of the Jacobian.
See http://www.kvraudio.com/forum/viewtopic.php?t=385262 for more
discussion of the idea.
This patch contains a test implementation of a nonlinear ladder filter,
closely following Antti Huovilainen's 2004 paper. It's hidden behind an
ifdef, though, as it's not ready for prime time.
Fixes various crashes, by (a) disabling the stats gathering thread and
(b) only trying to open a USB device if it identifies itself as a MIDI
keyboard. Disabling stats gathering should improve responsiveness and
improve battery consumption as well.
The crash in the stats gathering thread was a race on destruction, where
the audio thread set the stats_ringbuffer to NULL, but the Java thread
continued to try to read from it. This could be made more robust.
This version was published to Play Store as 0.91.
Train patch didn't render right. Should investigate further, but in
the meantime swap out one that does. Also narrow filter range,
increase touch count to 10, and fix pitch env for L4 != 50 case
(take-off patch).
Add a 512x512 px high res icon (needed for Play Store upload) and also
Inkscape source. It's a redrawing of the original lower-res bitmaps,
pretty close but not exact.
The "com.google" namespace is reserved for official releases, so
renaming to "com.levien".
Also small tweaking to piano2.xml to clean it up for release (arguably
should have been separate commit, but oh well).
This patch implements log2, which is necessary for amplitude modulation
(including amplitude LFO).
Also fixes up command line main.cc to track Dx7 init changes. (The
accuracy test is in that file).
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.
Finally implements detune (using an approximation, but better than
nothing). Also minor improvements to note generation, including scaling
output level more accurately, and getting rid of dynamic allocations of
note objects.
Add a button to capture raw start and end callback time (just putting it
in a text buffer so it can be copied), which is useful for making plots.
Also a bunch of commented out code to provoke priority inversion or
sudden increases in load (which exercises the governor), again for the
purpose of probing performance and making plots.
I was seeing thread context switches in systrace which looked like they
may have been caused by a mutex held by sprintf, so I replaced it with
a handrolled version (which should be a little faster anyway).
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 android_glue unit now collects timestamp stats and reports them up
through a ring buffer to the app. The app currently just displays a raw
line in a text view, but we'll expand that out to smarter aggregation.
On API 17+ (JellyBean MR1), get the buffer size and sample rate from the
platform, and use that, rather than hardcoding the defaults. We're still
using an internal buffer size (N) hardcoded to 64, so the amount of
computation per callback is not as consistent as it would be if that
were more flexible.
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).
This patch adds the low-level implementation of an LFO, with the DX7
waveforms, but doesn't yet contain the note wiring. It also adds a fast
lookup table based exp function, which is mostly used for envelopes.
There are also some build tweaks. It's possible some build files are
out of sync with the source, but at least the Android app seems to
build.
More sophisticated note stealing (better than round robin) and also
implementation of sustain (on midi controller 64). This implementation
matches the DX7 precisely.
Parameter changes and the like should work with unpacked patches,
so now we have an explicit patch unpack. In the future, the unpacking
will move out of the Dx7Note constructor.
This change adds a (single) resonant filter to the C++ synth unit, and
wires up both USB MIDI and on-screen controls for cutoff and resonance.
Also fixes a bug in KnobView which caused the knob value to jump around.
We were only using a very few STL functions (min, max, and iostream for
debug logging). This patch gets rid of those dependencies (implementing
the needed functions in synth.h), and turns on the "all" ABI target, so
that it works with all native architectures supported by the NDK.
This patch wires up pressure sensitivity from the touchscreen. It also
adds simple USB Host mode for MIDI keyboards (tested on M-Audio KeyRig 49
and Akai MPK mini). Finally, it cleans up a bit.
The USB listening thread should be moved out of the activity and into a
service (there can be problems on multiple plug and unplug). But this
should be good enough to play with.
Raph Levien
Gregory Schlomoff
Bryan Klimt