DigiDesign Digidesign Pro Tools 8.0, Reference Manual

Page: 790 / 1112

Pro Tools Reference Guide 772
Elastic Audio Analysis
When recording, pasting, moving, or importing
un-analyzed audio to an Elastic Audio-enabled
track, or when enabling Elastic Audio on an ex-
isting audio track, Pro Tools automatically ana-
lyzes the audio for transient events. In Wave-
form view, the waveform initially appears
grayed out because regions go offline during
Elastic Audio analysis. Once the analysis is com-
plete, the audio comes back online. Elastic Au-
dio analysis is file-based, which means that even
if you are only working with a small region of a
large file, the entire audio file is analyzed.
Elastic Audio analysis detects transient events in
the audio file. These transient events are indi-
cated by Event markers. Event markers are dis-
played in both the Warp and Analysis track
views. Elastic Audio analysis also calculates the
native tempo of the analyzed audio file and its
duration in bars and beats.
Elastic Audio analysis data (detected events,
tempo, and duration in Bars|Beats) is stored with
the file. In DigiBase browsers, analyzed audio
files are indicated by a check mark to the left of
the file name, and these files display their dura-
tion in Bars|Beats, their timebase as ticks, and
their native tempo in BPM.
Tempo Detection
Elastic Audio analysis does its best to detect a
regular tempo for all analyzed audio. Any audio
containing regular periodic rhythm can be suc-
cessfully analyzed for tempo and duration in
bars and beats. Analyzed files in which a tempo
was detected are treated as tick-based files. Tick-
based files can be conformed to the session
tempo for preview and import.
Analyzed files in which no tempo was detected
are treated as sample-based files. If there is only
a single transient in the file (such as with a sin-
gle snare hit), no tempo will be detected. Also,
longer files that contain tempo changes or ru-
bato, or that do not contain regular periodic
rhythmic patterns will probably not have a de-
tected tempo and will be treated as sample-
based files.
Event Confidence
Transient events are detected with a certain de-
gree of confidence. The level of confidence is
based on the relative clarity of transients.
For example, a drum loop is likely to have clear,
sharp transients. These will be detected with a
high degree of confidence. However, a legato vi-
olin melody may not have clear, sharp tran-
sients, so transients will be detected with a lower
degree of confidence.
Note that peak amplitude is not the most
important measure for event confidence.
The clarity of transients is measured in part
by the spectral transition from one moment
to the next. This tends to favor higher fre-
quency content in terms of event confidence.
For example, changing the Event Sensitivity
in the Elastic Properties window for a se-
lected drum loop results in the clearer tran-
sients of the higher frequency hi-hat hits
having more event confidence than the less
well defined transients of the lower fre-
quency kick drum hits even though kick
drum hits have a higher peak amplitude.