Dithering; Timestretch - Toshiba Gigabeat F Series User Manual

Digital audio players

Table of Contents

Chapter 6. Sound Settings

Simple EQ. This option provides an easier alternative for those who are daunted by all

of the parameters that can be adjusted using the graphical EQ. With the Simple

EQ, the only parameter that can be adjusted is the gain.

Advanced EQ. This sub menu provides options for adjusting the same parameters as the

Graphical EQ. The only diﬀerence is that the parameters are adjusted through

textual menus rather than through a graphic interface.

Save EQ Preset. This option saves the current EQ conﬁguration in a .cfg ﬁle.

Browse EQ Presets. This menu displays a list of EQ presets, as well as any EQ con-

ﬁgurations saved using the Save EQ Preset option. Users unfamiliar with the

operation of a parametric EQ may wish to use the presets instead of trying to

conﬁgure the EQ, or use the presets for designing their own custom EQ settings.

6.9. Dithering

This setting controls the dithering and noise shaping functionality of Rockbox.

Most of Rockbox' audio ﬁle decoders work at a higher bit depth than the 16 bits used

for output on the player's audio connectors. The simplest way to convert from one bit

depth to another is simply discarding all the surplus bits. This is the default behaviour,

and adds distortion to the signal that will vary in character along with the desired sound.

Dithering adds low-level noise to the signal prior to throwing away the surplus bits,

which gives the resulting signal a uniform noise ﬂoor which is independent of the sig-

nal. Most people ﬁnd this noise preferable to the time-varying noise heard when not

performing dithering.

After dithering, noise shaping is performed. This basically just pushes the dithering

noise to the parts of the frequency spectrum humans cannot hear so easily. In Rockbox'

case, some of the noise is pushed up to above 10 kHz.

This setting will be put to its best use when listening to dynamic music with frequently

occuring quiet parts, classical music being a typical example. It is worth noting that the

eﬀects of dithering and noise shaping are very subtle, and not easily noticable.

Rockbox uses highpass triangular distribution noise as the dithering noise source, and

a third order noise shaper.

Enabling Timestretch allows you to change the playback speed without it aﬀecting the

pitch of the recording. After enabling this feature and rebooting, you can access this via

the Pitch Screen. This function is intended for speech playback and may signiﬁcantly

dilute your listening experience with more complex audio.

The Rockbox manual

Toshiba Gigabeat F and X Series

Table of Contents