Ableton Live Intro Manuel d'instructions télécharger pdf (Page 377)

CHAPTER 31. MIDI FACT SHEET 375

environment would capture this incoming information with perfect timing accu-

racy in relation to the timeline of the song  as accurately as an audio recording.

2) Playback refers to two related scenarios when dealing with DAWs. The rst in-

volves sending MIDI note and controller information from the DAW to a hardware

device such as a synthesizer. The second involves converting stored MIDI infor-

mation into audio data within the computer, as played back by a plug-in device

such as the Operator synthesizer. In both cases, an ideal playback environment

would output a perfect reproduction of the stored information.

3) Playthrough involves sending MIDI note and controller information from a hard-

ware device (such as a MIDI keyboard) into the DAW and then, in real-time, back

out to a hardware synthesizer or to a plug-in device within the DAW. An ideal

playthrough environment would feel as accurate and responsive as a physical

instrument such as a piano.

31.2 MIDI Timing Problems

The realities of computer-based MIDI are complex, and involve so many variables that

the ideal systems described above are impossible to achieve. There are two fundamental

issues:

1) Latency refers to inherent and consistent delay in a system. This is a particular

problem in a DAW because digital audio cannot be transferred into or out of an

audio interface in real time, and must instead be buffered. But even acoustic

instruments exhibit a certain degree of latency; in a piano, for example, there is

some amount of delay between the time a key is depressed and the time the

hammer mechanism actually activates the string. From a performance perspec-

tive, small latency times are generally not a problem because players are usually

able to adapt the timing of their playing to compensate for delays  as long as

the delays remain consistent.

2) Jitter refers to inconsistent or random delay in a system. Within a DAW, this

can be a particular problem because different functions within the system (e.g.,

MIDI, audio and the user interface) are processed separately. Information often

needs to be moved from one such process to another  when converting MIDI

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Ableton Live Intro Manuel d'instructions Page 377