M-AUDIO Pro Tools Recording Studio - Manual (Page 812)

Pro Tools Reference Guide 794
Fades and MicroFades
Fades and Elastic Audio Processing
When applying fades to warped regions (regions
that have been processed by Elastic Audio), the
audio selected for the fade is first rendered and
then the fade is generated based on the rendered
audio file. While you can create fades and cross-
fades on regions on Elastic Audio-enabled
tracks, neither Real-Time nor Rendered Elastic
Audio processing can be applied to fades. Con-
sequently, fades always retain their absolute du-
ration and fades must be recalculated after any
Elastic Audio processing has been applied to the
underlying audio.
For example, if you change the session tempo, a
region on a tick-based Elastic Audio-enabled
track will change its duration (in minutes and
seconds) to match the new tempo, but any fades
that are part of that region do not change dura-
tion. The underlying audio is processed to
match the tempo change, then it is rendered,
and then the fade is regenerated. Even though
the underlying audio changes, the absolute du-
ration of the fade does not.
In Warp view, you will notice that Event mark-
ers never appear in fades and that Warp markers
cannot be added within fades. As a general rule,
apply fades to regions on Elastic Audio-enabled
tracks only after you have finished any manual
warp editing.
Microfades
Real-time Elastic Audio processing is not com-
pletely deterministic. Consequently, depending
on where you start playback, the part of a region
being played might actually be a few samples
longer or shorter. When fades or crossfades are
applied to warped regions, the audio waveform
at the boundary between the (real-time) region
and the (rendered) fade may not actually be con-
tinuous.
For example, if there are two butt-spliced re-
gions on a Real-Time Elastic Audio-enabled
track, Elastic Audio processes them separately
even though they are contiguous on the track.
As a result, the audio may not really be contigu-
ous after Elastic Audio processing and there may
be an audible pop when playing back across the
transition between the two regions.
To help compensate, Pro Tools applies micro-
fades to region boundaries on Real-Time Elastic
Audio-enabled tracks. Microfades are small real-
time fades at region boundaries intended to mit-
igate artifacts across region boundaries, or be-
tween an Elastic Audio processed region and a
rendered Fade file. Microfades are very short;
they are only about 1.5 milliseconds long (64
samples at 44 kHz, 128 samples at 96 kHz, and
256 samples at 192 kHz).
Approximate Waveforms
Another consequence of Real-Time Elastic Au-
dio processing is that the drawing of the wave-
forms is only approximate. For example, if you
bus record a Real-Time Elastic Audio processed
track, you will notice that the Waveform on the
source track does not necessarily exactly match
the recorded track. However, be assured that
what you hear is an accurate rendition of the
Real-Time Elastic Audio processing even if the
waveform drawing on the source track is only
approximate.
Region groups that contain regions with
fades are not allowed on Elastic Audio-en-
abled tracks.