103ebf77ce
git-svn-id: svn://svn.rockbox.org/rockbox/trunk@9820 a1c6a512-1295-4272-9138-f99709370657
288 lines
14 KiB
TeX
Executable file
288 lines
14 KiB
TeX
Executable file
% $Id$ %
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\screenshot{configure_rockbox/images/ss-sound-settings}{The sound settings screen}{}
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The Sound Settings menu offers a selection of sound properties you may
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change to customize your listening experience.
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\section{Volume}
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This control adjusts the volume of your music. Like most professional
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audio gear and many consumer audio products, Rockbox uses a decibel scale
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where 0 dB is a reference that indicates the maximum volume that the \dap\
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can produce without distortion (clipping). Because the volume control
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is basically a comparison of the volume level you set to a reference
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maximum volume of 0 dB, the usable range of the volume setting is shown
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as a negative number. Volume can be adjusted from a
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\opt{player}{minimum of -78 dB to a maximum of +18 dB.}
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\opt{recorder,recorderv2fm,ondio}{minimum of -100 dB to a maximum of +12 dB.}
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\opt{h1xx,h300}{minimum of -84 dB to a maximum of 0 dB.}
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\opt{ipodnano}{minimum of -72 dB to a maximum of +6 dB.}
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\opt{ipodvideo}{minimum of -57 dB to a maximum of +6 dB.}
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\opt{ipodcolor,x5}{minimum of -\fixme{??} dB to a maximum of +\fixme{??} dB.}
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\section{Bass}
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\opt{player,recorder,recorderv2fm,ondio}{This emphasises or suppresses the
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lower (bass) sounds in the track. 0 means that bass sounds are unaltered
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(flat response).}
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\opt{h1xx,h300}{The Bass setting can be used to increase (but not decrease)
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frequencies below 300Hz. Bass boost can be set from 0 to 24 dB in
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increments of 2 dB. A setting of 0 means that low frequencies are unaltered
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(flat response).}
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\opt{ipodnano,ipodcolor,ipodvideo,x5}{\fixme{TODO - platform specific description.}}
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\section{Treble}
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\opt{player,recorder,recorderv2fm,ondio}{This emphasises or suppresses the
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higher (treble) sounds in the track. 0 means that treble sounds are
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unaltered (flat response).}
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\opt{h1xx,h300}{The Treble setting can be used to increase (but not decrease)
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frequencies above 1.5kHz. Treble boost can be set from 0 to 6 dB in
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increments of 2 dB. A setting of 0 means that high frequencies are unaltered
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(flat response).}
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\opt{ipodnano,ipodcolor,ipodvideo,x5}{\fixme{TODO - platform specific description.}}
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\section{Balance}
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This setting controls the balance between the left and right channels. The
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default, 0, means that the left and right outputs are equal in volume.
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Negative numbers increase the volume of the left channel relative to the
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right, positive numbers increase the volume of the right channel relative
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to the left.
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\section{Channels}
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A stereo audio signal consists of two channels, left and right. The channels
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function controls how much of the left channel signal is mixed into the
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right channel signal, and vice versa.
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\opt{MASCODEC}{This option controls the on{}-board mixing facilities of the \dap.}
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\opt{SWCODEC}{This option controls the mixing facilities of the \dap.}
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Available options are:
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%
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\begin{table}
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\begin{center}
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\begin{tabularx}{\textwidth}{lX}\toprule
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\textbf{Setting} & \textbf{Description} \\\midrule
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Stereo
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& Do not mix the signal. \\
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%
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Mono
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& Mix both channels down to mono and send the mixed signal back to
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both. \\
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%
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Custom
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& Allows you to manually specify a stereo width with the
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\setting{Stereo Width} setting described later in this chapter. \\
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%
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Mono Left
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& Plays the left channel in both stereo channels. \\
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%
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Mono Right
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& Plays the right channel in both stereo channels. \\
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%
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Karaoke
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& Removes all sound that is the same in both channels. Since most
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vocals are recorded in this way to make the artist sound central,
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this often (but not always) has the effect of removing the voice
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track from a song. This setting also very often has other undesirable
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effects on the sound. \\
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\bottomrule
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\end{tabularx}
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\end{center}
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\end{table}
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\section{Stereo Width}
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Stereo width will allow you to manually specify the effect that is applied
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when the \setting{Channels} setting is set to \setting{Custom}.
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All values below 100\% will progressively mix the contents of one channel into
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the other. This has the effect of gradually centering the stereo image, until
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you have mono sound at 0\%. Values above 100\% will progressively remove
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components in one channel that is also present in the other. This has the
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effect of widening the stereo field. A value of 100\% will leave the stereo
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field unaltered.
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\opt{recorder,recorderv2fm}{
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\section{Loudness}
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Loudness is an effect which emphasises bass and treble. This makes the
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track seem louder by amplifying the frequencies that the human ear finds
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hard to hear. Frequencies in the vocal range are unaffected, since the human
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ear picks these up very easily.
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}
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\opt{recorder,recorderv2fm}{
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\section{Auto Volume}
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Auto volume is a feature that automatically lowers the volume on loud parts,
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and then slowly restores the volume to the previous level over a time
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interval. That time interval is configurable here. Short values like 20ms
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are useful for ensuring a constant volume for in car use and other
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applications where background noise makes a constant loudness desirable.
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A longer timeout means that the change in volume back to the previous level
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will be smoother, so there will be less sharp changes in volume level.
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}
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\opt{recorder,recorderv2fm}{
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\section{Super Bass}
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This setting changes the threshold at which bass frequencies are affected by
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the \setting{Loudness} setting, making the sound of drums and bass guitar
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louder in comparison to the rest of the track. This setting only has an
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effect if \setting{Loudness} is set to a value larger than 0dB.
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}
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\opt{recorder,recorderv2fm}{
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\section{MDB {}- Micronas Dynamic Bass}
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The rest of the parameters on this menu relate to the Micronas Dynamic
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Bass (MDB) function. This is designed to enable the user to hear bass
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notes that the headphones and/or speakers are not capable of reproducing.
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Every tone has a fundamental frequency (the ``main tone'') and also several
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harmonics, which are related to that tone. The human brain has a mechanism
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whereby it can actually infer the presence of bass notes from the higher
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harmonics that they would generate.
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The practical upshot of this is that MDB produces a more authentic sounding
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bass by tricking the brain in believing it's hearing tones that the
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headphones or speakers aren't capable of reproducing. Try it and see
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what you think.
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The MDB parameters are as follows.
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%
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\begin{description}
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\item[MDB enable:]
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This turns the MDB feature on or off. For many users this will be the
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only setting they need, since Rockbox picks sensible defaults for the
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other parameters. MDB is turned off by default.
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\item[MDB strength:]
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How loud the harmonics generated by the MDB will be.
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\item[MDB Harmonics:]
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The percentage of the low notes that is converted into harmonics.
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If low notes are causing speaker distortion, this can be set to 100\%
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to eliminate the fundamental completely and only produce harmonics in the
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signal. If set to 0\% this is the same as turning the MDB feature off.
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\item[MDB Centre Frequency:]
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The cutoff frequency of your headphones or speakers. This is usually
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given in the specification for the headphones/speakers.
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\item[MDB shape:]
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It is recommended that this parameter be set to 1.5 times the centre frequency.
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This is the frequency up to which harmonics are generated. Some of the
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lower fundamentals near the cut{}-off range will have their lower
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harmonics cut off, since they will be below the range of the speakers.
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Fundamentals between the cut{}-off frequency and the lower frequency
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will have their harmonics proportionally boosted to compensate and restore
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the `loudness' of these notes.
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For most users, the defaults should provide an improvement in sound
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quality and can be safely left as they are. For reference, the defaults
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Rockbox uses are:
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%
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\begin{table}[h!]
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\begin{center}
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\begin{tabular}{@{}lc@{}}\toprule
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Setting & Value \\\midrule
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MDB Strength & 50dB \\
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MDB Harmonics & 48\% \\
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MDB Centre Frequency & 60Hz \\
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MDB Shape & 90Hz \\\bottomrule
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\end{tabular}
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\end{center}
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\end{table}
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\end{description}
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}
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\opt{SWCODEC}{
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\section{Crossfeed}
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Crossfeed attempts to make the experience of listening to music on
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headphones more similar to listening to stereo speakers. When you listen
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to music through speakers, your right ear hears sound from the left speaker
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and vice versa. However, the sound from the left speaker reaches your left
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ear slightly later than the sound from your right ear, and vice versa.
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Moreover, when listening to speakers, you hear the direct sound from the
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speakers, but you also hear reflections of that sound as the sound waves
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bounce off of walls, floors, ceilings, etc. These reflections reach your
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ears slightly after the direct sound.
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The human ear and brain are very good at interpreting the timing differences
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between direct sounds and reflected sounds and using that information to
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identify the direction that the sound is coming from. On the other hand,
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when listening to headphones, your ear hears only the direct sounds, and
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not reflections. Moreover, your left ear hears only the left channel and
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the right ear hears only the right channel. The result is that sound from
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headphones does not provide the same spatial cues to your ear and brain as
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speakers.
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The crossfeed function uses an algorithm to feed a delayed and filtered
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portion of the signal from the right channel into the left channel and vice
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versa in order to simulate the spatial cues that the ear and brain receive
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when listening to a set of loudspeakers placed in front of the listener. The
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result is a more natural stereo image that can be especially appreciated in
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older rock and jazz records, where one instrument is often hard-panned to just
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one of the speakers. Many people will find such records tiring to listen to
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using earphones and no crossfeed effect.
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Crossfeed has the following settings.
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\begin{description}
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\item[Crossfeed:]
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Selects whether the crossfeed effect is to be enabled or not.
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\item[Direct Gain:]
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How much the level of the audio that travels the direct path from a speaker
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to the corresponding ear is supposed to be decreased.
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\item[Cross Gain:]
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How much the level of the audio that travels the cross path from a speaker
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to the opposite ear is to be decreased.
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\item[High-Frequency Attenuation:]
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How much the upper frequencies of the cross path audio will be dampened.
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Note that the total level of the higher frequencies will be a combination
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of both this setting and the \setting{Cross Gain} setting.
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\item[High-Frequency Cutoff]
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Decides at which frequency the cross path audio will start to be cut
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by the amount described by the \setting{High-Frequency Attenuation} setting.
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\end{description}
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Most users will find the default settings to yield satisfactory results, but
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for the more adventurous user the settings can be fine-tuned to provide a
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virtual speaker placement suited to ones preference.
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% TODO: adapt the guidelines for crossfeed settings found here?
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% http://www.ohl.to/interests-in-audio/crossfeed-and-eq-for-headphones/
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Beware that the crossfeed function is capable of making the audio distort
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if you choose settings which result in a too high output level.
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}
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\opt{SWCODEC}{
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\section{Equalizer}
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\screenshot{configure_rockbox/images/ss-equalizer}{The graphical equalizer}{}
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Rockbox features a parametric equalizer. As the name suggests, a parametric
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equalizer lets you control several different parameters for each band of the
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equalizer. Rockbox's parametric EQ is composed of five different EQ bands:
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\begin{description}
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\item[Band 0: Low shelf filter.] A low shelf filter boosts or lowers all
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frequencies below the designated cutoff point. The ``bass''control on
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most home or car stereos is an example of a low shelf filter. The low shelf
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filter in Rockbox is more flexible than a simple ``bass'' control, because
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a simple bass control only lets you adjust the amount of gain that is
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applied. Rockbox lets you control the amount of gain that is applied
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(i.e., the amount that the bass is boosted or cut) too, but Rockbox also
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allows you to adjust the ``cutoff'' frequency where the shelving starts
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to take effect. For example, a cutoff frequency of 50 Hz will adjust only
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very low frequencies. A cutoff frequency of 200 Hz, on the other hand,
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will adjust a much wider range of bass frequencies.
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\item[Bands 1-3: Peaking filters.]
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Peaking EQ filters boost or low a center frequency that you select, as
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well as the frequencies within a certain distance of that center. Graphic
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equalizers in home stereos are usually peaking filters. The peaking EQs
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on Rockbox's parametric equalizer let you adjust three different
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parameters for each EQ band 1 through 3. The ``center'' parameter
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controls the center frequency that is adjusted by that EQ band. The
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``gain'' parameter controls how much each band is adjusted. Positive
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numbers make the EQ band louder, while negative numbers make that EQ band
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quieter. Finally, the ``Q'' parameter controls how wide or narrow each EQ
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band is. Higher Q values will affect a narrow band of frequencies, while
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lower EQ values will affect a wider band of frequencies.
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\item[Band 4: High shelf filter.]
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A high shelf filter boosts or lowers all frequencies above a designated
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cutoff point. The ``treble'' control on most home or car stereos is an
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example of a high shelf filter. The high shelf filter is adjusted the
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same way as the low shelf filter, except that it works on the high end
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of the frequency spectrum rather than the low end.
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\end{description}
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So, as a general guide, EQ band 0 should be used for lows, EQ bands 1
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through 3 should be used for mids, and EQ band 4 should be used for highs.
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You can find more information about setting the parametric equalizer and
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using equalizer presets in the Advanced Topics chapter of this manual.
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}
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