This control adjusts the volume of your music. Like most professional audio gear and many consumer audio products, Rockbox uses a decibel scale where 0 dB is a reference that indicates the maximum volume that the \dap\ can produce without distortion (clipping). Because the volume control is basically a comparison of the volume level you set to a reference maximum volume of 0 dB, the usable range of the volume setting is shown as a negative number.
\opt{player,recorder,recorderv2fm,ondio}{This emphasises or suppresses the lower (bass) sounds in the track. 0 means that bass sounds are unaltered (flat response).}
\opt{h1xx,h300}{The Bass setting can be used to increase (but not decrease) frequencies below 300Hz. Bass boost can be set from 0 to 24 dB in increments of 2 dB. A setting of 0 means that low frequencies are unaltered (flat response).}
\opt{ipodnano,ipodcolor,ipodvideo}{TODO - platform specific description.}
\opt{player,recorder,recorderv2fm,ondio}{This emphasises or suppresses the higher (treble) sounds in the track. 0 means that treble sounds are unaltered (flat response).}
\opt{h1xx,h300}{The Treble setting can be used to increase (but not decrease) frequencies above 1.5kHz. Treble boost can be set from 0 to 6 dB in increments of 2 dB. A setting of 0 means that high frequencies are unaltered (flat response).}
\opt{ipodnano,ipodcolor,ipodvideo}{TODO - platform specific description.}
This setting controls the balance between the left and right channels. The default, 0, means that the left and right outputs are equal in volume. Negative numbers increase the volume of the left channel relative to the right, positive numbers increase the volume of the right channel relative to the left.
A stereo audio signal consists of two channels, left and right. The channels function controls how much of the left channel signal is mixed into the right channel signal, and vice versa.
\opt{MASCODEC}{This option controls the on{}-board mixing facilities of the \dap.}
Mono Left & Plays the left channel in both stereo channels. \\
%
Mono Right & Plays the right channel in both stereo channels. \\
%
Mono & Mix both channels down to mono and send the mixed signal back to both. \\
%
Stereo & Do not mix the signal. \\
%
Stereo Narrow & Mixes small amounts of the opposite channel into the left and right channels, thus making the sound seem closer together. \\
%
Stereo Wide & Elements of one channel that are present in the opposite channel are removed from the latter. This results in the sound seeming further apart. \\
%
Karaoke & Removes all sound that is the same in both channels. Since most vocals are recorded in this way to make the artist sound central, this often (but not always) has the effect of removing the voice track from a song. \\
\bottomrule
\end{tabularx}
\opt{recorder,recorderv2fm}{
\section{Loudness}
Loudness is an effect which emphasises bass and treble. This makes the track seem louder by amplifying the frequencies that the human ear finds hard to hear. Frequencies in the vocal range are unaffected, since the human ear picks these up very easily.
Auto volume is a feature that automatically lowers the volume on loud parts, and then slowly restores the volume to the previous level over a time interval. That time interval is configurable here. Short values like 20ms are useful for ensuring a constant volume for in car use and other applications where background noise makes a constant loudness desirable. A longer timeout means that the change in volume back to the previous level will be smoother, so there will be less sharp changes in volume level.
This setting changes the threshold at which bass frequencies are affected by the \textbf{Loudness} setting, making the sound of drums and bass guitar louder in comparison to the rest of the track. This setting only has an effect if \textbf{Loudness} is set to a value larger than 0dB.
The rest of the parameters on this menu relate to the Micronas Dynamic Bass (MDB) function. This is designed to enable the user to hear bass notes that the headphones and/or speakers are not capable of reproducing. Every tone has a fundamental frequency (the ``main tone'') and also several harmonics, which are related to that tone. The human brain has a mechanism whereby it can actually infer the presence of bass notes from the higher harmonics that they would generate.\\
The practical upshot of this is that MDB produces a more authentic sounding bass by tricking the brain in believing it's hearing tones that the headphones or speakers aren't capable of reproducing. Try it and see what you think.\\
This turns the MDB feature on or off. For many users this will be the only setting they need, since Rockbox picks sensible defaults for the other parameters. MDB is turned off by default.
\item\textbf{MDB strength:}
How loud the harmonics generated by the MDB will be.
\item\textbf{MDB Harmonics:}
The percentage of the low notes that is converted into harmonics. If low notes are causing speaker distortion, this can be set to 100\% to eliminate the fundamental completely and only produce harmonics in the signal. If set to 0\% this is the same as turning the MDB feature off.
\item\textbf{MDB Centre Frequency: }The cutoff frequency of your headphones or speakers. This is usually given in the specification for the headphones/speakers.
\item\textbf{MDB shape: }It is recommended that this parameter be set to 1.5 times the centre frequency.\\
This is the frequency up to which harmonics are generated. Some of the lower fundamentals near the cut{}-off range will have their lower harmonics cut off, since they will be below the range of the speakers. Fundamentals between the cut{}-off frequency and the lower frequency will have their harmonics proportionally boosted to compensate and restore the 'loudness' of these notes.\\
For most users, the defaults should provide an improvement in sound quality and can be safely left as they are. For reference, the defaults Rockbox uses are:
Crossfeed attempts to make the experience of listening to music on headphones more similar to listening to stereo speakers. When you listen to music through speakers, your right ear hears sound from the left speaker and vice versa. However, the sound from the left speaker reaches your left ear slightly later than the sound from your right ear, and vice versa. Moreover, when listening to speakers, you hear the direct sound from the speakers, but you also hear reflections of that sound as the sound waves bounce off of walls, floors, ceilings, etc. These reflections reach your ears slightly after the direct sound.
The human ear and brain are very good at interpreting the timing differences between direct sounds and reflected sounds and using that information to identify the direction that the sound is coming from. On the other hand, when listening to headphones, your ear hears only the direct sounds, and not reflections. Moreover, your left ear hears only the left channel and the right ear hears only the right channel. The result is that sound from headphones does not provide the same spatial cues to your ear and brain as speakers.
The crossfeed function uses an algorithm to feed a delayed and filtered portion of the signal from the right channel into the left channel and vice versa in order to simulate the spatial cues that the ear and brain receive when listening to non-headphone sources. The result is a better stereo image.
}
\opt{SWCODEC}{
\section{Equalizer}
Rockbox features a parametric equalizer. As the name suggests, a parametric equalizer lets you control several different parameters for each band of the equalizer. Rockbox's parametric EQ is composed of five different EQ bands:
\begin{itemize}
\item\textbf{Band 0: Low shelf filter. }A low shelf filter boosts or lowers all frequencies below the designated cutoff point. The ``bass''control on most home or car stereos is an example of a low shelf filter. The low shelf filter in Rockbox is more flexible than a simple ``bass'' control, because a simple bass control only lets you adjust the amount of gain that is applied. Rockbox lets you control the amount of gain that is applied (i.e., the amount that the bass is boosted or cut) too, but Rockbox also allows you to adjust the ``cutoff'' frequency where the shelving starts to take effect. For example, a cutoff frequency of 50 Hz will adjust only very low frequencies. A cutoff frequency of 200 Hz, on the other hand, will adjust a much wider range of bass frequencies.
\item\textbf{Bands 1-3: Peaking filters.} Peaking EQ filters boost or low a center frequency that you select, as well as the frequencies within a certain distance of that center. Graphic equalizers in home stereos are usually peaking filters. The peaking EQs on Rockbox's parametric equalizer let you adjust three different parameters for each EQ band 1 through 3. The ``center'' parameter controls the center frequency that is adjusted by that EQ band. The ``gain'' parameter controls how much each band is adjusted. Positive numbers make the EQ band louder, while negative numbers make that EQ band quieter. Finally, the ``Q'' parameter controls how wide or narrow each EQ band is. Higher Q values will affect a narrow band of frequencies, while lower EQ values will affect a wider band of frequencies.
\item\textbf{Band 4: High shelf filter.} A high shelf filter boosts or lowers all frequencies above a designated cutoff point. The ``treble'' control on most home or car stereos is an example of a high shelf filter. The high shelf filter is adjusted the same way as the low shelf filter, except that it works on the high end of the frequency spectrum rather than the low end.
