XO Wave is now discontinued
as we prepare to bring you the next generation
Digital Audio Workstation called
This site remains available for anyone who
purchased XO Wave in the past.
However, please keep in mind that as discontinued software:
- This site may not contain up-to-date information.
- Technical support is discontinued, though we will do our best to continue to provide
email support, especially to anyone who purchased recently.
XO Wave: Waveform Display
|Figure 1. Several waveforms
and overviews from a segment of "Secret Heart"
from Let It Die, written by Ron Sexsmith and performed
by Feist. (a) shows the
waveform overview zoomed out. Some peaks and
troughs may not be visible at this zoom level.
(b) shows the waveform overview zoomed in. The
slightly blocky appearance signifies we have
reached the resolution limit of the overview.
(c) shows the waveform zoomed out. At this
level, some peaks and troughs in the waveform
may not be visible. (d) shows the waveform
zoomed in. A great deal of detail is visible at
Waveforms are graphical representations of audio. They are useful for sound
editing because different sections of audio can be visually identified
quickly and efficiently -- especially once you have a little experience
working with waveforms. Before computers, recordings could be edited
by painstakingly splicing tape together. This was difficult not only
because of the labor involved, but also because everything had to be
done by ear alone. Additionally, fixing mistakes in spliced tape could
be expensive or impossible.
Today, software such as XO Wave displays high-resolution
graphical representations of the audio, easily distinguishing beats,
loud and quiet sections, and even parts of notes and speech, greatly
aiding in the editing process.
Sound is fundamentally our perception of tiny fluctuations in air pressure, so it can be visualized as
waveforms by graphing air pressure over time. Sounds
usually cause the pressure to fluctuate above and below some
average pressure. In general, waveforms from louder sounds
extend further from the middle than softer sounds, because they
cause more extreme changes in air pressure. Sounds with high
frequencies change quickly, often exhibiting a
jagged or rough appearance, while sounds with lower frequencies exhibit
slower shifts up and down. Sounds with both high and low frequencies
can often be identified as having both frequent rough edges
and longer swings above and below the middle of the graph.
XO Wave has an advanced and flexible method of displaying audio waveforms.
The general approach is similar to the approach taken by many
other audio software packages, although XO Wave gives you greater
flexibility. Most of the time, you won't need to
understand the details, but if you want to know exactly how
XO Wave displays waveforms, or if you want to change the way waveforms
are displayed, this document will help.
How Audio Waveforms and Overviews Are Displayed
By default, waveforms are displayed when you are zoomed in and "waveform
overviews" are displayed when you are zoomed out. The waveform overview,
or simply "overview", is a low resolution
approximation of the true waveform which is computed when you
record or import a file (or when you select Rebuild All
Overviews from the
Region Bin menu).
saved in the session's
AudioFiles directory, with
Because they are pre-computed, overviews allow for very fast display of audio data
when zoomed out; however, because overviews do not contain complete
information, it is important to remember that they are only an
approximation of the real audio waveform.
By default, overviews are displayed as filled-in graphs, as shown in
Figure 1a. As you zoom in, the overview acquires a blockier appearance,
as shown in Figure 1b, indicating the resolution limit of the overview
has been reached. Zooming in further causes the overview to be
replaced by a waveform display as shown in Figure 1c. By default,
waveforms are displayed as lines, which easily distinguishes them
from the filled-in shapes of the overviews. Note that until
you zoom even further in, such as in Figure 1d, the waveform may skip
over some peaks and troughs in order to speed drawing. If this
is a problem in your scenario,
you may change the zoom level at which waveforms are
used in lieu of overviews, to see the true waveforms sooner when zooming in.
Changing Waveform and Overview Display Options
The Preferences window allows
you to change the way waveforms and overviews are displayed in
XO Wave's Edit window.
To adjust these settings, select
XO Wave:Preferences... on Mac OS X or
Windows:Preferences... on Linux. Then
select the Edit tab, as shown.
The Preferences window provides several options, the results of which are
illustrated in Figure 2, below.
- Draw Rectified Overview: Turning this feature
on causes overviews to be displayed as a graph ascending from
the bottom, as shown in Figure 2b, rather than a graph ascending and descending from
the middle (Figure 2a). Some engineers regard this
as superior because
it effectively uses less screen-space and provides an
additional visual cue that the overview and not the waveform
is being displayed. However, most engineers
find rectified overviews awkward to work with.
- Draw Rectified Waveform: Turning this feature
on causes waveforms to be displayed as a graph ascending from
the bottom, rather than a graph ascending and descending from
the middle. However, unlike overviews,
waveforms are not symmetrical about the middle of the graph,
and so this view necessarily discards some information. You can
get that information back by activating Use Inv
Waveform Color, described below, to achieve something more like
- Fill Overview: Turning this off causes the
overviews graphs not to be filled, as shown in Figure 2c.
On some platforms with slower graphics cards, this has been
found to improve drawing speed slightly.
- Fill Waveform: Turning this on causes the
waveform graphs to be filled in, as shown in Figure 2e.
Some people find this easier
to view, while others prefer to retain the obvious
distinction between waveforms and overviews.
- Minimum Edit Length: Controls the number of pixels
the mouse must move during an edit for XO Wave to
consider an edit to have taken place. This setting
provides a slight "snap" to the cursor's original location
while editing. It may be useful to set this higher if you
have shaky hands, a poor mouse, or a
- Show Region Name in Region: Allows you to
show or hide the region's name in the Edit window.
- Show File Name in Region: Allows you to
show or hide the region's source file name in the Edit
- Use Inv Waveform Color: Turning this on
causes XO Wave to display the negative section of a waveform
using a different color (specified in the Preferences window
under the Color tab). This is most useful in
conjunction with Draw Rectified Waveform, where it can be
used to distinguish positive and negative waveform sections
as shown in Figure 2f.
- Zoom Mag: Controls the zoom level at which
XO Wave's display changes from overview to waveform.
This is useful in case you want to avoid blocky overviews
or you want to make sure that no peaks or troughs are missed
when viewing a waveform.
- .5: Use this setting if you want to
guarantee that waveforms are never shown unless
all peaks and troughs can be represented.
- 1: Use this setting if you want
a large degree of certainty that waveform
displays will show all peaks and troughs.
- 10: This setting provides a
balance between fast & smooth and accurate
display, favoring accuracy a bit more than
the default setting.
- 25: The default settings gives a
balance between fast & smooth and accurate
- 100: Use this setting to avoid
seeing blocky overviews.
a) default overviews
b) rectified overviews
c) un-filled overviews
d) default waveforms
e) filled waveforms
f) filled, rectified, colored waveforms
|Figure 2. A few
different ways of viewing waveforms and
overviews in XO Wave. (a) shows the default
overviews. (b) shows overviews rectified. (c) shows
non-filled overviews which draw slightly faster
on some platforms. (d) shows default waveforms.
e) shows waveform filled. (f) shows waveforms
filled, rectified, and using the inverse waveform