Pro Tools lets you set any track timebase to either sample-based or tick-based. You can also set the Timeline to be viewed as tick-based or sample-based.
Audio in Pro Tools is sample-based by default. This means that if an audio clip is located at a particular sample location, it will not move from that location if the tempo changes in the session—though its Bar|Beat location
will change.
MIDI data in Pro Tools is tick-based by default. This means that if a MIDI clip is located at a particular Bar|Beat location, it will not move from that Bar|Beat location if the tempo changes in the session—though its sample location
will change.
You can select whether a track is sample-based or tick-based when it is created, or change timebases later.
With a sample-based audio track, all clips in the track have an absolute location on the Timeline. Clips stay fixed to the sample time, regardless of where tempo or meter changes occur in a session.
If you make a MIDI track sample-based, all MIDI events in the track have an absolute location on the Timeline. MIDI events stay fixed to sample time, regardless of any tempo or meter changes in a session.
Tick-based audio is fixed to a Bars|Beat location, and moves relative to the sample Timeline when tempo and meter changes occur. However, MIDI events and tick-based audio respond differently to tempo changes with respect to duration. MIDI note events change length when tempo or meter is adjusted, while audio clips do not (unless Elastic Audio is enabled). When Elastic Audio is
not enabled on an audio track, meter and tempo changes affect only the start point (or sync point) for each audio clip in a tick-based track. If Elastic Audio is enabled on an audio track, tempo changes apply Elastic Audio processing, which changes the duration of the audio clip.
Elastic Audio provides real-time and non-real-time (rendered) Time Compression and Expansion (TCE) of audio. Tick-based Elastic Audio tracks actually change the location of samples according to changes in tempo. The audio stretches or compresses to match changes in tempo. Elastic Audio also provides high-quality non-real-time clip-based pitch shifting.
Pro Tools Elastic Audio uses exceptionally high-quality transient detection algorithms, beat and tempo analysis, and real-time or rendered TCE processing algorithms. Elastic Audio lets you quickly and easily tempo conform and beat match audio to the session’s Tempo ruler. It also provides an unprecedented degree of control over transient detection and TCE processing on an event-by-event basis.
With Elastic Audio, Pro Tools analyzes entire audio files for transient “events.” For example, an event can be a drum hit, a sung note, or chord played by a guitar. These detected events can then serve as control points for “warping” the audio. Pro Tools can warp (TCE) audio events automatically, such as when automatically conforming audio to the session tempo or quantizing audio events, or you can warp audio manually using the standard editing tools with the audio track set to Warp view.
Elastic Audio is useful in several common workflows: working with loops, correcting performances, remixing, beat and pitch matching, and sound design and special effects.