Reference Manual

586 MIDI Fact Sheet
to a schedule. Additionally, MIDI cables are serial, meaning they can only send one piece of
information at a time. In practice, this means that multiple notes played simultaneously cannot
be transmitted simultaneously through MIDI cables, but instead must be sent one after the other.
Depending on the density of the events, this can cause MIDI timing problems.
Another issue that can arise, particularly when working with hardware synthesizers from the
early days of MIDI, is that the scan time of the device may occur at a relatively slow rate. Scan
time refers to how often the synthesizer checks its own keyboard for input. If this rate is too slow,
jitter may be introduced.
Of course, any such timing problems present at the hardware level may be multiplied as addi-
tional pieces of gear are added to the chain.
Even within the computer, the accuracy of timestamps can vary widely, depending on the quality
of the MIDI hardware, errors in driver programming, etc. Live must assume that any timestamps
attached to incoming MIDI events are accurate, and that outgoing events will be dealt with ap-
propriately by any external hardware. But both situations are impossible for Live to verify.
Tests and Results
Our procedure for testing the timing of incoming MIDI events is represented in the following
diagram:
MIDI Input Test Configuration.
The output of a MIDI Source (a keyboard or other DAW playing long sequences of random
MIDI events) is fed to a zero-latency hardware MIDI Splitter. One portion of the splitter‘s output
is recorded into a new MIDI clip in Live. The other portion is fed to a MIDI-to-Audio Converter.
This device converts the electrical signal from the MIDI source into simple audio noise. Because
the device does not interpret the MIDI data, it performs this conversion with zero-latency. The
MIDI Source
MIDI
Splitter
MIDI-to-Audio
Converter
Live
MIDI Clip
Audio Clip