koppi / alsa-midi-latency-test

== 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
 * yamaha-ux256.txt     PC -> Yamaha UX256 (6-Port) -> 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 <jakob.flierl@gmail.com>

-- November, 2009