7 The default stereo panner distributes 2 inputs to 2 outputs. Its
8 behaviour is controlled by two parameters, width and position. The
9 default settings for the stereo panner are width=100%,
10 position=center (L=50%, R=50%). This panner assumes that the signals
11 you wish to distribute are either uncorrelated (that means totally
12 independent), or they contain a stereo image which is
13 mono-compatible<sup><ahref="#caveat">*</a></sup>.
17 With the default values it is not possible to alter the position,
18 since the width is already spread entirely across both outputs. To
19 alter the position, you must first reduce the width.
23 <h2>Stereo Panner User Interface</h2>
25 <img src="/images/stereo-panner-annotated.png" alt=""/>
28 The panner user interface consists of 3 elements, divided between
29 the top and bottom half. Click and/or drag in the top half to
30 control position; click and/or drag in the bottom half to control
31 width (see below for details).
34 In the top half is the position indicator, which shows where the
35 center of the stereo image is relative to the left and right
36 edges. When this is the middle of the panner, the stereo image is
37 centered between the left and right outputs. When it all the way to
38 the left, the stereo image collapses to just the left speaker.
41 In the bottom half are two signal indicators, one marked "L" and the
42 other "R". The distance between these two shows the width of the
43 stereo image. If the width is reduced to zero, there will only be a
44 single signal indicator marked "M" (for mono), and whose color will
45 change to indicate the special state.
48 It is possible to invert the outputs (see below) so that whatever
49 would have gone to the right channel goes to the left and vice
50 versa. When this happens, the entire movable part of the panner
51 changes color to indicate clearly that this is the case.
54 <h3>Position vs. L/R</h3>
57 Although the implementation of the panner uses the "position"
58 parameter, when the user interface displays it numerically, it shows a pair of numbers that
59 will be familiar to most audio engineers.
63 <tr><th>Position</th><th>L/R</th><th>English</th></tr>
64 <tr><td>0</td><td>L=50% R=50%</td><td>signal image is midway between
65 left and right speakers</td></tr>
67 <tr><td>-1</td><td>L=100% R=0%</td><td>signal image is entirely
68 at the left speaker </td></tr>
70 <tr><td>1</td><td>L=0% R=100%</td><td>signal image is entirely
71 at the right speaker</td></tr>
75 One way to remember this sort of convention is that the middle of the
76 USA is not Kansas, but "Los Angeles: 50% New York: 50%".
79 <h2>Examples In Use</h2>
82 <tr><th>Appearance</th><th>Settings</th></tr>
83 <tr><td><img src="/images/stereo-panner.png"></td><td>Width=100%,
85 <tr><td><img src="/images/stereo-panner-zero.png"></td><td>Width=0%,
87 <tr><td><img src="/images/stereo-panner-inverted.png"></td><td>Width=-100%, Position = 0 (center)</td></tr>
88 <tr><td><img src="/images/stereo-panner-right.png"></td><td>Width=36%,
90 <tr><td><img src="/images/stereo-panner-hard-right.png"></td><td>Width=0%,
94 <h2>Using the mouse</h2>
97 Mouse operations in the upper half of the panner adjust the position
98 parameter, constrained by the current width setting.
101 Mouse operations in the lower half of the panner adjust the width
102 parameter, constrained by the current position setting.
105 To change the position smoothly, press the right button and drag
106 within the top half of the panner, then release. The position will
107 be limited by the current width setting. <em>Note: you do not need
108 to grab the position indicator in order to drag</em>
111 To change the width smoothly, press the right button and drag
112 within the lower half of the panner, then release. The width will be
113 limited by the current position setting.<em>Note: you do not need to
114 grab the L/R indicators in order to drag</em>
119 <dt>Reset to defaults</dt>
120 <dd>Click <key class="mod3">right button</key></dd>
122 <dt>Change to a "hard left"</dt>
123 <dd>Double click <key class="mod2">right button</key> in the upper left half
126 <dt>Change to a "hard right"</dt>
127 <dd>Double click <key class="mod2">right button</key> in the upper right half
130 <dt>Move position as far left as possible, given width</dt>
131 <dd>Double click <key>right button</key> in the upper left half of the
134 <dt>Move position as far right as possible, given width</dt>
135 <dd>Double click <key>right button</key> in the upper right half of the
138 <dt>Set the position to center</dt>
139 <dd>Click <key>right button</key> in the upper middle of the panner</dd>
141 <dt>Reset to maximum possible width</dt>
142 <dd>Double click <key>right button</key> on the lower left side</dd>
144 <dt>Invert (flip channel assignments)</dt>
145 <dd>Double click <key>right button</key> on the lower right side</dd>
147 <dt>Set width to 0°</dt>
148 <dd>Double click <key>right button</key> in the lower middle</dd>
151 <h4>Keyboard bindings</h4>
154 When the pointer is within a stereo panner user interface, the following
155 keybindings are available to operate on that panner:
159 <dt><key>↑</key> / <key class="mod1">↑</key></dt>
160 <dd>increase width by 1° / 5°</dd>
161 <dt><key>↓</key> / <key class="mod1">↓</key></dt>
162 <dd>decrease width by 1° / 5°</dd>
163 <dt><key>←</key> / <key class="mod1">←</key></dt>
164 <dd>move position 1° / 5° to the left</dd>
165 <dt><key>→</key> / <key class="mod1">→</key></dt>
166 <dd>move position 1° / 5° to the right</dd>
167 <dt><key>0</key></dt>
168 <dd>reset position to center</dd>
169 <dt><key class="mod2">↑</key></dt>
170 <dd>reset width to full (100%)</dd>
173 <h4>Using the scroll wheel/touch scroll</h4>
176 When the pointer is within a stereo panner user interface, the scroll
177 wheel may be used as follows:
181 <dt>left / <key class="mod1">left</key></dt>
182 <dd>increase width by 1° / 5°</dd>
184 <dt>right / <key class="mod1">right</key></dt>
185 <dd>decrease width by 1° / 5°</dd>
187 <dt>up / <key class="mod1">up</key></dt>
188 <dd>move position 1° / 5° to the left</dd>
190 <dt>down / <key class="mod1">down</key></dt>
191 <dd>move position 1° / 5°to the right</dd>
194 <h2><a name="caveat" />Panning caveats</h2>
197 Note that the stereo panner will introduce unwanted side effects on
198 material that includes a time difference between the channels, such
199 as AB, ORTF or NOS microphone recordings, or delay-panned mixes.<br />
200 With such signals, when you reduce the with, you are summing two signals
201 with different delays, which will introduce comb filtering.
204 Let's take a look at what happens when you record a source at 45° to the
205 right side with an ORTF array (cardioids, spacing 17cm, opening angle
207 The time difference is 350 usecs or approximately 15 samples at 44k1. The
208 level difference due to the directivity of the microphones is about 7.5dB.
210 <img src="/images/stereo-panner-with-ORTF-fullwidth.png" />
212 For testing, we apply a pink noise signal, which displays as a straight line
213 in the analyser. To simulate an ORTF, we use Robin Gareus' stereo balance
214 control LV2 to set the level difference and time delay. Ignore the Trim/Gain
215 - its purpose is just to align the test signal with the 0dB line of the
219 Now for the interesting part: if we reduce the width of the signal to 50%,
220 the time-delayed signals will be combined in the panner. Observe what
221 happens to the frequency response:
223 <img src="/images/stereo-panner-with-ORTF-halfwidth.png" />
225 Depending on your material and on how much you need to manipulate the width,
226 the comb filter may be acceptable. Then again, it may not be. Listen
227 carefully for artefacts if you manipulate unknown stereo signals - many
228 orchestra sample libraries for example do contain time-delay components.