Nokia N77 - About Encoded Audio; Variable Bitrate

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Media applications
40
About encoded audio
Applications like Windows Media Player and Nokia Audio
Manager in Nokia Nseries PC Suite (available on the
CD-ROM supplied with your device) encode audio files
with codecs such as WMA or MP3 to save storage space.
The encoding is done by removing those parts of the audio
signal that are not audible or only barely audible by human
ear.
Regardless of the encoder and codec quality, the sound
quality of the resulting file is not as good as the original.
The basic codecs supported by this device are AAC, WMA,
and MP3. All of these have different variations. Music
player does not necessarily support all features of a file
format or all the variations of file formats.
Bitrates
When encoding audio, the quality of the resulting sound
depends on the sample rate and bit rate used for the
encoding. Sample rate is expressed as thousands of
samples per second (kHz), and for CD music, the sample
rate is fixed at 44.1 kHz. Bit rate is expressed as kilobits per
second (Kbps). The higher the bit rate, the better the sound
quality.
The required quality level may depend on your demands,
the headsets used, and the surrounding noise. For MP3s a
bitrate between 128 and 192 Kbps usually gives results
good enough for listening to pop music with your device.
WMA or AAC generally gives a similar result as MP3 with
one step lower bit rate (96–160 Kbps). Variations of AAC,
such as AAC+ and enhanced AAC+ (eAAC+) provide CD
quality audio at bitrates as low as 48 Kbps. Classical music
and music with nuances usually require a higher bit rate
than basic pop music.
For speech or other sources where the quality of the sound
is less important than saving storage space, you can use bit
rates between 8 and 64 Kbps. At low bit rates WMA or AAC
generally gives better results than MP3.
Variable bitrate
Your device also supports variable bit rate (VBR). VBR
means that the bit rate of the encoding varies with the
complexity of the encoded material. When using VBR, the
encoding is optimized to preserve a constant audio quality
throughout the track rather than losing quality for
complex music sections as with constant bit rate (CBR)
encoding.