== Intro ==

alsa-midi-latency-test measures the roundtrip time of a MIDI message in the alsa subsystem of the linux kernel using a high precision timer. It calculates the worst case roundtrip time of all sent MIDI messages and displays a histogram of the rountrip time jitter.

== Compiling, installing and running ==

The following libraries are required to build alsa-midi-latency-test:

• debhelper (>= 5)
• autotools-dev
• automake
• libasound2-dev (>= 1.0.13)

Compile and install alsa-midi-latency-test as follows:

$ sh autogen.sh $ ./configure $ make $ sudo make install

Run alsa-midi-latency-test as follows:

$ alsa-midi-latency-test -l

Lists available MIDI input and output ports.

$ alsa-midi-latency-test -i [input port] -o [output port]

This runs the benchmark with the given input and output port. Note, that the input and output ports have to be connected using a MIDI cable in the real hardware to loop the MIDI message back.

$ man alsa-midi-latency-test

The man page contains documentation for all available command line switches.

== Results ==

Results of some benchmarks created with alsa-midi-latency-test can be found in the benchmarks/ sub-directory. The setup of the MIDI-chains of the results is as follows:

• elektron-tm1.txt: PC -> Elektron TM-1 -> PC
• gm5x5x5.txt: PC -> Polytec GM5 www.midibox.org -> PC
• ua25ex.txt: PC -> Edirol UA-25EX -> PC
• midisport2x2ann.txt: PC -> MidiSport 2x2 'Anniversary Edition' port B -> PC
• mpu401.txt: PC -> MPU-401-Port on motherboard -> PC
• um2ex.txt: PC -> Edirol UM-2EX -> PC

If you have an interesting setup, please send us you results so we can include them here for further reference.

== See also ==

• http://www.linuxaudio.org/mailarchive/lat/

  The linux-audio tuning (LAT) mailing list is to help GNU/Linux distribution maintainers and other interested users to share information on system performance tuning matters, especially with regard to real-time Linux kernels.

• http://www.alsa-project.org

  The Advanced Linux Sound Architecture.

== Website ==

The project is hosted at github.com:

http://github.com/koppi/alsa-midi-latency-test/tree/master

== Thanks ==

• to Arnout Engelen for initial testing and giving feedback.
• to Clemens Ladisch for a number of fixes with the high precision timer and alsa midi event handling.

== BUGS and AUTHORS ==

This is an early release. Please report bugs to the authors.

• Jakob Flierl [email protected]

-- November, 2009