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When <b>DRC Power</b> is decreasd dynamic range compression will have
less influence at output. Zero <b>DRC Power</b> level means that dynamic
range compression applied at normal.
<h4><b>* CPU load.</b><br>
</h4>
Indicates CPU load by sound decoding and processing.
All sound processing (if exists) before reproduction included here.
<h4><b>* Input/output levels.</b><br>
</h4>
<font color="#000000"> Current audio levels
indication for each channel. Note that levels here are in logarithmic
scale. Input levels shows <i>real</i> channels configuration. Often
happens that when BSI shows 5.1 in real LFE channel is absent</font><font color="#000000"> (read <a href="file:///E:/&USERS/VA/PROJECTS/AC3Filter/AC3Filter/ac3filter_0_67b/ac3filter_eng.html#lfe">What
is LFE?</a> section for more information about this). If output levels
become red it indicates overflow and you need to decrease gain.<br>
</font>
<h4><font color="#000000">* Presets</font></h4>
<font color="#000000"> This section allows to manage
persets. You can load/save/delete presets. Several predefined presets
are available:<br>
</font>
<ul>
<li><font color="#000000"><b>standard</b> - maximum standard
compatibility</font></li>
<li><font color="#000000"><b>loud</b> - as named, for maximum
loudness.</font></li>
<li><font color="#000000"><b>LFE boost</b> - LFE boosted at +10dB.</font></li>
</ul>
<font color="#000000"> You can also load/save presets
to/from file with <b>file</b> button:<br>
</font>
<div align="center"><font color="#000000"><img src="pic/preset.gif" title="" alt="" width="273" height="157"><br>
</font></div>
<font color="#000000"><br>
Configuration file may be saved with the same name
as movie (proposed by default). In this case this configuration will be
loaded automatically with movie.<br>
All filter settings are divided to several
categories. It is recommended to save only general settings (and maybe
equalizer) to autoloaded config files because in future you may watch
this movie at different system. Settings that not in configuration file
are not altered with file load.</font><br>
<br>
<h3><a name="mixer"></a>Mixer settings</h3>
Second page is mixer settings. <br>
<br>
<div align="center"><img src="pic/mixer.gif" title="" alt="" width="628" height="429"> <br>
</div>
<br>
For convenience some controls from Main page are
placed here. For its description look at <a href="file:///E:/&USERS/VA/PROJECTS/AC3Filter/AC3Filter/ac3filter_0_67b/ac3filter_eng.html#main_settings">Main
settings</a>.<br>
<br>
Main controls here are mixing matrix. It is in form
of matrix multiplication: S' = M*S, where S = { L, C, R, SL, SR, LFE } -
input sample, S' = { L', C', R', SL', SR', SW' } - output sample.<br>
<br>
More simple it means next rule for each cell: we mix
channel specified by column to channel specified by row with gain
specified in cell. So if we want to route left channel to right speaker
we should set 1 in cell at cross of 'L' column and 'R' row. If we don't
want to hear left channel from left speakers anymore then we set 0 at
cross 'L' column and 'L' row. If we make same operation with right and
surround channel then we fully swap left and right channel. (Note, that
in this case we fully swap 'L' and 'R' rows).<br>
<br>
It is nessesary to clearly distinct concepts of
input and output channels. Input channel is what was coded in AC3
stream. Output channel is what we'll hear from speakers.<br>
<br>
Row determines what we'll hear from corresponding
output channel. For matrix shown above from left chanel we'll hear 1
part of input left channel, part of center channel, lowered left
surround and LFE.<br>
<br>
Column determines where input channel will be mixed.
For matrix shown above center channel will be routed to left and right
channel with factor 0.7. So we'll hear center channel in center of left
and right speakers. If we make it louder in one of speakers then center
will be 'shifted' toward this speaker.<br>
<br>
When <b>Auto matrix</b> is enabled then matrix is
automatically calculated and changed with parameters change. For example
if we change <b>Center</b> level we'll see factors change in 'C' column.<br>
<br>
Settings description:<br>
<ul>
<li><b>Auto gain control</b> - automatic gain control. It controls
current gain to prevent overflow. Curent gain is shown at <b>Gain</b>
level. When this option is disabled high-level signal is clipped on
overflow what leads to unpleasant distortions. When this option is
enabled then current gain will be decreased and overflow does not
happen. System behavior after overflow is defined by <b>One-pass
normalize</b> option. If <b>One-pass normalize</b> is disabled then
current gain will be gradually restored up to <b>Master</b> level. In
this case <b>Master</b> defines mean gain level. If it is many places
when overflow occurs then this behavior can lead to unpleasant
'jumps' of audio level. In this case do not set <b>Master</b> level too
high. This mode is recommended if overflow is not expected. If <b>One-pass
normalize</b> option is enabled then gain level will not be restored
after overflow. So each overflow decreases probability and 'strength' of
next overflow and after some time gain will be stabilized to some mean
value. Usually it happens after about ~10min of film playback. In this
case <b>Master</b> level means initial gain for one pass normalization
algorithm and may be set to maximum. This mode can provide maximum
loudness with minimal artifacts. (see also <a href="#max_loud">Maximum
loudness</a>)<br>
</li>
<li><b>One-pass normalize</b> - one pass normalizaion. See <b>Auto
gain control</b>.</li>
<li><b>Auto matrix</b> - automatic calculation of mixer matrix. When
this option is enabled matrix editing direct is disabled. Gain levels
for <b>LFE</b>, <b>Voice</b> and <b>Surround</b> are parameters for
matrix calculation. When this option is disabled next controls loose
influence: gain levels for <b>LFE</b>, <b>Voice</b> and <b>Surround</b>,<b>
Normalize matrix</b>, <b>Expand stereo</b>, <b>Voice control</b>, <b>Expand
stereo</b>. Following controls are remain to work: <b>Master</b>, <b>Gain</b>,<b>
DRC level</b>, <b>DRC power</b>, <b>One-pass normalize</b>. Direct
matrix edit is enabled.</li>
<li><b>Normalize marix</b> - matrix normalization. When this option is
enabled matrix is normalized so it is no overflow at output (sum of
channels at output < 1). But when one of gain levels (<b>LFE</b>, <b>Voice</b>
or <b>Surround</b>) changes other gain level will be also changed
(for example if we increase level of LFE all other channels level will
be decreased). If this option is disabled it allows to avoid this
effect. But overflow is possible in this case. So it is better to
decrease <b>Master</b> gain when this option is disabled.</li>
<li><b>Expand stereo</b> - works only if it is no surround channels in
AC3 stream. In this case it allows to amplify surround information with <b>Surround</b>
gain control (that have no effect by default if it is not surround
channels at input). If it is surround channels at output this option
will route surround information there, i.e. allows surround upmix.
Techincally it controls out-of-phase audio components (channel
differences) and routes it to surround channels if they are exists.<br>
</li>
<li><b>Voice control</b> - works only if it is no center channel in
AC3 stream. In this case it allows to control center with <b>Voice</b>
gain control (that have no effect by default in absence of center
channel at input). If it is center speaker specified at output
configuration then this option will route center signal there. With <b>Expand
stereo</b> option allows full stereo to multichannel upmix. I.e. make
center and surround speakers to work even if input is just stereo.
Techincally it controls in-phase audio components (equal in both
channels) and routes it to center speaker if it is exists.<br>
</li>
<li><b>B</b><b>ass redir</b> - Bass redirection. Route basses from all
channels to subwoofer. Works only if it is subwoofer at output speakers.
Highly recommended for systems with separate subwoofer (look <a href="#lfe">What is LFE?</a>). Basses are routed before mixing so
basses are shown at LFE input level (although 'real' LFE may be absent).
Cutoff frequency is 375Hz (for 48000Hz sampling frequency).</li>
</ul>
Combo-box allows to save and load saved matrices.<br>
<br>
<h3><a name="equalizer"></a>Equalizer and delays.</h3>
<div align="center"><img src="pic/equalizer.gif" title="" alt="" width="628" height="427"><br>
</div>
<br>
Right part is fully about equalizer. Everything is
obvious so I will not bother myself with full description ;-).<br>
<br>
Left top corner are delay settings to compensate
different distances to speakers. Ideally all speakers should be at equal
distance to listener so sound emitted simultaneously from all speakers
reach listener at the same time. Otherwise sound picture will be
distorted. But in practice distance to speakers may be different. To
compensate this difference sound should be delayed.<br>
<br>
Delay value may be set directly in ms or samples.
Negative value means that channel should be reproduced 'earlier' than
'null time' (if speaker is placed farther then it should start to work
earlier because sound needs more time to reach listener).<br>
<br>
For convenience it is possible to set distance to
speakers. In this case positive values means negative delay for speaker
start to work earlier. Negative values means positive delay.<br>
<br>
<br>
<hr width="100%" size="2">
<h2><a name="lfe"></a>What is LFE?</h2>
<br>
First and most important thing is that LFE is not
the same thing as subwoofer! And 5.1 in case of AC3 is not the same as
5.1 in case of computer acoustics.<br>
<br>
AC3 format was created for cinema rather than
computer acoustics. In theaters acoustics is well enough to reproduce
low frequencies. LFE channel was designed for powerful low frequency <i>effects</i>,
i.e. effects that usual acoustics cannot handle. So all channels in ac3
stream contains low frequencies and LFE works only in certain moments to
help main speakers to quake the walls and earth. And it is quite
possible that LFE will not be enabled during the film. And it is normal.<br>
<br>
Computer acoustics is totally different. Most of 5.1
systems cannot reproduce low frequencies through satellites at all. So
subwoofer must work all the time.<br>
<br>
So if we connect 5.1 acoustics and start to watch
movie with 5.1 sound track with subwoofer designated only for LFE
channel we will not hear basses at all!<br>
<br>
Threrfore if acoustics have separate subwoofer it is
highly recommended to route there basses from all channels (since <i>all</i>
channels have basses). I.e. enable <b>Bass redirection</b> in filter
properties. Or use analogous option in sound card driver settings (if
exists) and turn filter option off. Some may ask about 'right' playback.
This people should read this document: (<a href="http://www.dolby.com/tech/c.in.0011.LFE.pdf">http://www.dolby.com/tech/c.i
n.0011.LFE.pdf</a>) with explanation about LFE role and how to handle
it. <br>
<br>
<br>
<hr width="100%" size="2">
<h2><a name="cookbook"></a>Cookbook.</h2>
<h3><a name="lfe_mix"></a> LFE mixing.</h3>
When it is no separate subwoofer at output
configuration LFE is mixed only to front channels. If rear channels are
powerful enough we can mix LFE there for louder effects: <br>
<ul>
<li>Start film playback<br>
</li>
<li>Open filter's properties (note that WMP v7+ does not allow this!).<br>
</li>
<li>Turn <b>Auto Matrix</b> off.</li>
<li>In LFE matrix column set '1' (for example) in SR and SL rows</li>
<li>Save this matrix.</li>
</ul>
<br>
<h3><a name="swap_speakers"></a> Swap channels.</h3>
For better understanding read <a href="#mixer">Mixer
settings</a> section first (at mixer matrix description).<br>
<br>
Do you want real center channel on 4- channel sound
card? It is possible. Of cource it is impossible to get 5 channels out
of 4-channel sound card but we can use one of rear speakers as center,
i.e. make 3/1 (3 front / 1 rear) configuration instead of 2/2 (2 front /
2 rear).
<ul>
<li>Start film playback.</li>
<li>Turn <b>Auto Matrix</b> on. (it will allow to get basis matrix).</li>
<li>Set 3/1 output configuration. By now we have no center channel so
center will be mixed to front channels by drivers. But we'll trick them
later.<br>
</li>
<li>Set our favorite settings (gain levels, etc) </li>
<li>Turn <b>Auto Matrix</b> off.</li>
<li>At this stage we have basis matrix. We will play cener through
rear right speaker. So copy all values from '⌨️ 快捷键说明
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