</p>
<p>
The stereo panner assumes that the signals
- you wish to distribute are either uncorrelated (i.e. totally
- independent), or that they contain a stereo image which is
- <dfn>mono-compatible</dfn>, such as a co-incident microphone recording, or a
+ you wish to distribute are either uncorrelated (i.e. totally
+ independent), or that they contain a stereo image which is
+ <dfn>mono-compatible</dfn>, such as a co-incident microphone recording, or a
sound stage that has been created with pan pots.<sup><a href="#caveat">*</a></sup>
</p>
<p class="note">
<h2>Stereo Panner User Interface</h2>
-<img src="/images/stereo-panner-annotated.png" alt=""/>
+<figure class="left">
+ <img src="/images/stereo-panner.png" alt="The Stereo Panner">
+ <figcaption>
+ The Stereo Panner
+ </figcaption>
+</figure>
+
<p>
The <dfn>panner user interface</dfn> consists of three elements, divided between
the top and bottom half. Click and/or drag in the top half to
center of the stereo image is relative to the left and right
edges. When this is the middle of the panner, the stereo image is
centered between the left and right outputs. When it all the way to
- the left, the stereo image collapses to just the left speaker.
+ the left, the stereo image collapses to just the left speaker.
</p>
<p>
In the bottom half are two signal indicators, one marked "L" and the
It is possible to invert the outputs (see below) so that whatever
would have gone to the right channel goes to the left and vice
versa. When this happens, the entire movable part of the panner
- changes color to indicate clearly that this is the case.
+ changes color to indicate clearly that this is the case.
</p>
<h3>Position vs. L/R</h3>
<p>
Although the implementation of the panner uses the "position"
- parameter, when the user interface displays it numerically, it shows
- a pair of numbers that will be familiar to most audio engineers.
+ parameter, when the user interface displays it numerically, it shows
+ a pair of numbers that will be familiar to most audio engineers.
</p>
-<table>
+<table class="nodl">
<tr><th>Position</th><th>L/R</th><th>English</th></tr>
<tr><td>0</td><td>L=50% R=50%</td><td>signal image is midway between
left and right speakers</td></tr>
<p>
One way to remember this sort of convention is that the middle of the
- USA is not Kansas, but "Los Angeles: 50% New York: 50%".
+ USA is not Kansas, but "Los Angeles: 50% New York: 50%".
</p>
<h3>Examples In Use</h3>
-<table>
+<table class="nodl">
<tr><th>Appearance</th><th>Settings</th></tr>
<tr><td><img src="/images/stereo-panner.png"></td><td>Width=100%,
L=50 R=50</td></tr>
<p>
Mouse operations in the upper half of the panner adjust the position
- parameter, constrained by the current width setting.
+ parameter, constrained by the current width setting.
</p>
<p>
Mouse operations in the lower half of the panner adjust the width
- parameter, constrained by the current position setting.
+ parameter, constrained by the current position setting.
</p>
<p>
To change the position smoothly, press the right button and drag
grab the L/R indicators in order to drag.</em>
</p>
-<dl class="faq">
+<table class="dl">
-<dt>Reset to defaults</dt>
-<dd>Click <kbd class="mod3 mouse">right</kbd></dd>
+<tr><th>Reset to defaults</th>
+<td>Click <kbd class="mod3 mouse">right</kbd></td></tr>
-<dt>Change to hard left</dt>
-<dd>Double click <kbd class="mod2 mouse">right</kbd> in the upper left half
- of the panner</dd>
+<tr><th>Change to hard left</th>
+<td>Double click <kbd class="mod2 mouse">right</kbd> in the upper left half
+ of the panner</td></tr>
-<dt>Change to a hard right</dt>
-<dd>Double click <kbd class="mod2 mouse">right</kbd> in the upper right half
- of the panner</dd>
+<tr><th>Change to a hard right</th>
+<td>Double click <kbd class="mod2 mouse">right</kbd> in the upper right half
+ of the panner</td></tr>
-<dt>Move position as far left as possible, given width</dt>
-<dd>Double click <kbd class="mouse">right</kbd> in the upper left half of the
- panner</dd>
+<tr><th>Move position as far left as possible, given width</th>
+<td>Double click <kbd class="mouse">right</kbd> in the upper left half of the
+ panner</td></tr>
-<dt>Move position as far right as possible, given width</dt>
-<dd>Double click <kbd class="mouse">right</kbd> in the upper right half of the
- panner</dd>
+<tr><th>Move position as far right as possible, given width</th>
+<td>Double click <kbd class="mouse">right</kbd> in the upper right half of the
+ panner</td></tr>
-<dt>Set the position to center</dt>
-<dd>Click <kbd class="mouse">right</kbd> in the upper middle of the panner</dd>
+<tr><th>Set the position to center</th>
+<td>Click <kbd class="mouse">right</kbd> in the upper middle of the panner</td></tr>
-<dt>Reset to maximum possible width</dt>
-<dd>Double click <kbd class="mouse">right</kbd> on the lower left side</dd>
+<tr><th>Reset to maximum possible width</th>
+<td>Double click <kbd class="mouse">right</kbd> on the lower left side</td></tr>
-<dt>Invert (flip channel assignments)</dt>
-<dd>Double click <kbd class="mouse">right</kbd> on the lower right side</dd>
+<tr><th>Invert (flip channel assignments)</th>
+<td>Double click <kbd class="mouse">right</kbd> on the lower right side</td></tr>
-<dt>Set width to 0°</dt>
-<dd>Double click <kbd class="mouse">right</kbd> in the lower middle</dd>
-</dl>
+<tr><th>Set width to 0°</th>
+<td>Double click <kbd class="mouse">right</kbd> in the lower middle</td></tr>
+</table>
<h4>Keyboard bindings</h4>
keybindings are available to operate on that panner:
</p>
-<dl>
- <dt><kbd>↑</kbd> / <kbd class="mod1">↑</kbd></dt>
- <dd>increase width by 1° / 5°</dd>
- <dt><kbd>↓</kbd> / <kbd class="mod1">↓</kbd></dt>
- <dd>decrease width by 1° / 5°</dd>
- <dt><kbd>←</kbd> / <kbd class="mod1">←</kbd></dt>
- <dd>move position 1° / 5° to the left</dd>
- <dt><kbd>→</kbd> / <kbd class="mod1">→</kbd></dt>
- <dd>move position 1° / 5° to the right</dd>
- <dt><kbd>0</kbd></dt>
- <dd>reset position to center</dd>
- <dt><kbd class="mod2">↑</kbd></dt>
- <dd>reset width to full (100%)</dd>
-</dl>
+<table class="dl">
+ <tr><th><kbd>↑</kbd> / <kbd class="mod1">↑</kbd></th>
+ <td>increase width by 1° / 5°</td></tr>
+ <tr><th><kbd>↓</kbd> / <kbd class="mod1">↓</kbd></th>
+ <td>decrease width by 1° / 5°</td></tr>
+ <tr><th><kbd>←</kbd> / <kbd class="mod1">←</kbd></th>
+ <td>move position 1° / 5° to the left</td></tr>
+ <tr><th><kbd>→</kbd> / <kbd class="mod1">→</kbd></th>
+ <td>move position 1° / 5° to the right</td></tr>
+ <tr><th><kbd>0</kbd></th>
+ <td>reset position to center</td></tr>
+ <tr><th><kbd class="mod2">↑</kbd></th>
+ <td>reset width to full (100%)</td></tr>
+</table>
<h4>Using the scroll wheel/touch scroll</h4>
wheel may be used as follows:
</p>
-<dl>
- <dt><kbd class="mouse">⇐</kbd> / <kbd class="mod1 mouse">⇐</kbd></dt>
- <dd>increase width by 1° / 5°</dd>
- <dt><kbd class="mouse">⇒</kbd> / <kbd class="mod1 mouse">⇒</kbd></dt>
- <dd>decrease width by 1° / 5°</dd>
- <dt><kbd class="mouse">⇑</kbd> / <kbd class="mod1 mouse">⇑</kbd></dt>
- <dd>move position 1° / 5° to the left</dd>
- <dt><kbd class="mouse">⇓</kbd> / <kbd class="mod1 mouse">⇓</kbd></dt>
- <dd>move position 1° / 5°to the right</dd>
-</dl>
+<table class="dl">
+ <tr><th><kbd class="mouse">⇐</kbd> / <kbd class="mod1 mouse">⇐</kbd></th>
+ <td>increase width by 1° / 5°</td></tr>
+ <tr><th><kbd class="mouse">⇒</kbd> / <kbd class="mod1 mouse">⇒</kbd></th>
+ <td>decrease width by 1° / 5°</td></tr>
+ <tr><th><kbd class="mouse">⇑</kbd> / <kbd class="mod1 mouse">⇑</kbd></th>
+ <td>move position 1° / 5° to the left</td></tr>
+ <tr><th><kbd class="mouse">⇓</kbd> / <kbd class="mod1 mouse">⇓</kbd></th>
+ <td>move position 1° / 5°to the right</td></tr>
+</table>
<h2><a name="caveat"></a>Stereo panning caveats</h2>
<p class="warning">
The stereo panner will introduce unwanted side effects on
material that includes a time difference between the channels, such
-as A/B, ORTF or NOS microphone recordings, or delay-panned mixes.<br>
+as A/B, ORTF or NOS microphone recordings, or delay-panned mixes.<br>
When you reduce the with, you are effectively summing two highly
correlated signals with a delay, which will cause <dfn>comb filtering</dfn>.
</p>
-<p>
+<p>
Let's take a closer look at what happens when you record a source at 45° to the
right side with an ORTF stereo microphone array and then manipulate the width.
</p>
<p>
For testing, we apply a <dfn>pink noise</dfn> signal to both inputs of an Ardour stereo
-bus with the stereo panner, and feed the bus output to a two-channel analyser.
+bus with the stereo panner, and feed the bus output to a two-channel analyser.
Since pink noise contains equal energy per octave, the expected readout is a
straight line, which would indicate that our signal chain does not color the
sound:
To simulate an ORTF, we use Robin Gareus' stereo balance control LV2 to set the level difference and time delay. Ignore the Trim/Gain—its purpose is just to align the test signal with the 0dB line of the analyser.
</p>
-<p>
+<p>
Recall that an <dfn>ORTF</dfn> microphone pair consists of two cardioids spaced 17 cm
apart, with an opening angle of 110°.
-For a far source at 45° to the right, the time difference between the capsules
-is 350 μs or approximately 15 samples at 44.1 kHz. The level difference
-due to the directivity of the microphones is about 7.5 dB (indicated by the
+For a far source at 45° to the right, the time difference between the capsules
+is 350 μs or approximately 15 samples at 44.1 kHz. The level difference
+due to the directivity of the microphones is about 7.5 dB (indicated by the
distance between the blue and red lines in the analyser).
</p>
<p>
</p>
<img src="/images/stereo-panner-with-ORTF-halfwidth.png" />
<p>
-You may argue that all spaced microphone recordings will undergo comb
+You may argue that all spaced microphone recordings will undergo comb
filtering later, when the two channels recombine in the air between the speakers.
Perceptually however, there is a huge of difference: our hearing system is
very good at eliminating comb filters in the real world, where their component
carefully for artefacts if you manipulate unknown stereo signals—many
orchestra sample libraries for example do contain time-delay components.
</p>
-
projects / ardour-manual / blobdiff