Chapter 6. Sound Settings
53
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.
6.11. Timestretch
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. See section
(page
) for more details about how to use the feature.
6.12. Haas Surround
This setting implements the Haas effect with adjustable delay time to enhance the stereo
effect of the sound. A full range Haas effect creates the impression that sound starts from
one channel and ends in the other. Therefore, four additional functions are provided to
move the stage back to the center:
Balance
to change the left-right channel output
ratio.
A bypass band for frequencies that mostly contain vocals, using
f(x1)
, and
f(x2)
to set frequencies which are not affected. The
SIDE ONLY
setting uses mid-side
processing to determine and apply effect to the side channel only. Finally, the
Dry/Wet
Mix
setting adjusts the proportion mixed from the original (dry) and ’effected’ (wet)
signals.
6.13. Perceptual Bass Enhancement
This setting implements a group delay correction and an additional biophonic EQ to
emphasize to boost bass perception. The
precut
setting provides negative overall gain
to prevent possible audio distortion due to the EQ gain. The defult precut value is set
to -2.5 dB and can be adjust from 0 dB to -4.5 dB. Note that this effect will stack with
any other EQ applied.
The Rockbox manual
(version 3.14)
Iaudio M5
