Ableton/Live/UG/40 MIDI Fact Sheet/04 Variables Outside of Live's Control
- Timestamps only exist inside the computer. External hardware acts on MIDI as soon as it arrives.
- MIDI cables are serial, so a chord's notes travel one after another; dense passages can smear timing.
- Older synths may scan their own keyboards slowly, adding jitter. Problems multiply as more devices join the chain.
- Live has to trust incoming timestamps and the handling of outgoing events, and can verify neither.
Tests and Results
- Input test: a MIDI source feeds a zero-latency splitter. One branch records into a MIDI clip; the other goes through a MIDI-to-audio converter into an audio clip. The offset between matching events measures Live's accuracy.
- Ableton tested three combined audio/MIDI interfaces, A, B and C, at about 50% CPU, on macOS and Windows, at 44.1 and 96 kHz and three buffer sizes: 36 configurations.
- Results: most jitter fell within ±1 ms on every interface. Worst cases ranged from ±4 ms (Windows, A) to ±10 ms (Windows, C at 44.1 kHz / 1024 samples) and ±11 ms (macOS, A and B at 44.1 kHz / 1152 samples). Interface C on macOS stayed within ±1 ms in every test.
- Output tests gave results comparable to input.
