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Glossary / Supplementary Information
CD
Compact Discs (CD) are digital data media which need to be handled carefully.
These are the basic rules:
•
The surface of a CD should only ever be cleaned with a soft dry cloth. Never
wipe it in a circular motion, i. e. along the tracks.
•
Never use petrol, paint thinners, disc cleaners or similar materials on
compact discs.
•
CDs must be handled carefully in order to avoid serious damage to the
surface. Severely scratched surfaces, writing on the disc or applying self-
adhesive labels may result in the CD player being unable to read the data.
•
CDs should not be heated or bent. This means that they should be stored in a
position and attitude which meet these requirements.
Digital filters
Digital audio signals are stored with a certain sampling rate of for example
44.1 kHz - i. e. for each second of music 44.100 sampled values are available
for each channel. In the
Music Player
the digital audio signals are converted
(upsampled) to a much higher sample rate (352,8 or 384 kHz) before they are
converted to analog signals by the D/A converter. This process delivers a very
much better, more finely graduated signal to the converter, which can then be
converted with correspondingly higher precision.
For the upsampling of the digital audio signals different algorithms are
implemented in the
Music Player
. You can choose between these algorithms
during music playback.
The different algorithms are described in more detail below.
Filter 1
(Standard FIR filter)
The long FIR filter is the standard oversampling process in digital technology,
offering extremely linear frequency response, very high damping, linear phase
charac-teristics and constant group delays. The disadvantage is the pre- and
post-echoes which are added to the signal. These „time domain errors“ tend to
affect the music signal’s dynamics, precision and naturalness, and reduce
spatial orientation.
Frequency response and transient characteristics of the long FIR filter
Filter 2
(Impulse optimised filter)
By shortening the filter length (lower number of filtercoefficients) the time
domain errors are reduced resulting in a better impuls response (less filter
‚ringing‘) Acoustically such a shorter filter will have a slightly less accurate
frequency response but higher dynamics and better imaging.
Frequency response and transient characteristics of the short FIR filter
