philburk/mobileer-synth

General MIDI Synthesizer used as a ringtone engine by Mobileer. Suitable for use on 32-bit embedded systems.

mobileer-synth

General MIDI Synthesizer in portable C by Mobileer.

This synthesizer was licensed for use in the Palm Treo and other mobile devices for playing ringtones.

The library is given MIDI bytes as input and produces 16-bit PCM audio as output. It can be easily connected to any audio system. Optional output modules can be used to play in real-time using PortAudio or to output a WAV file.

The library has 3 levels:

• ME1000 - is for low memory devices and uses a virtual analog synthesizer instead of wavetables
• ME2000 - adds wavetables for piano, violin, drums and other instruments that are difficult to synthesize
• ME3000 - adds support for DLS and Scalable Polyphonic MIDI ringtone standards

Documentation in docs folder

Dependencies and Requirements

The synthesizer uses 32-bit fixed-point arithmetic for its signal processing. It does not use floating point.

It has minimal software dependencies and can even run without a memory allocator on embedded devices with no operating system.

It does not require any file I/O. The wavetable instruments are loaded at compile time from a header produced by a custom editor.

The ME1000 requires:

• Memory
  • Code 20-30 KB ROM
  • Instrument Library 14 KB ROM
  • Data 20-30 KB RAM
• 32-bit integer arithmetic, eg ARM-7, Blackfin

The ME2000 adds more ROM for the wavetables, depending on quality. A 1 MB instrument set is included.

• On an ARM946 generating audio at 44100 Hz
  • each wavetable voice requires 1.5 MIPS
  • each synthesized voice requires 2.4 MIPS

Building

The current build system requires CMake and a C compiler.

This will generate a library for the ME2000 and a few example programs.

cd spmidi
mkdir build
cd build
cmake ..
make

The libraries will be in the "spmidi/build/lib" folder and the executables will be in the "spmidi/build/bin" folder.

This will play a diatonic scale and output the results to a WAV file.

bin/play_scale

If you have ALSA installed then you can hear the output:

aplay spmidi_output.wav

You can convert any standard MIDI file to WAV using "play_midifile". We have included some ringtones that you can use for testing.

bin/play_midifile ../../data/ringtones/phil/songs/FurryLisa_rt.mid
aplay spmidi_output.wav
bin/play_midifile ../../data/ringtones/phil/songs/Bach_Sonata3EMajor.mid
aplay spmidi_output.wav

Contributors

• Phil Burk - primary developer and sound designer
• Robert Marsanyi - DLS and other contributions to the ME3000
• Ryan Fransesconi - contributed to the instrument editor written in Java

mobileer-synth's Issues

Mobileer Instrument Editor availability

Requesting having Hybrid Editor as a free download, if feasible.
Would make exploring the synth engine more fun.

Release as open source

Devin Magruder [email protected] wrote:

have you ever considered releasing the ME-series synth tools and the source code to the synth there?
There may not be much immediate interest but I feel that those interested in embedded MIDI/FM
synthesizers (like those found in older phones) would appreciate the contribution.

Please release smaller than 1 MB wavetables and API docs

I have read on the old product website, that there were smaller wavetables as well.
Can you please release them, so that I can use it on a ESP32 or other embedded system ?
Also, it seems as if the official API documentation (aside from the comments in the headers) are missing.

Add Apache Open Source License

to the source files