Datasheet

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VS1053B OGG VORBIS ENCODER VSMPG
and song length, and while it makes it easier to stream files, CBR is not optimal for qual-
ity. When there is a difficult passage in music, there may not be enough bits available to
encode audio flawlessly. Conversely, in passages that are easier to encode there may
be bits left unused because the encoder didn’t need all the bits available in the bitstream.
Where CBR tries to keep the bit-rate constant regardless of content, Variable Bit-Rate
(VBR) tries to keep quality constant. This will have the effect of changing the bit-rate of
the file depending on how difficult a particular portion of music is to encode. Because
sound quality is always kept constant, VBR has a bit advantage to CBR. Thus, VBR
allows either for smaller files with the same perceived sound quality or equally sized
files with better perceived sound quality.
Ogg Vorbis is by nature a variable bit-rate format and works best when this feature is
not limited. Depending on the material the bit-rate can have significant fluctuations: e.g.
songs that have been compressed with a quality setting with a nominal bit-rate of 96
kbit/s can easily have average bit-rates between 80 to 105 kbit/s, or even more with
extreme material.
3.1.2 Transcoding
Transcoding is the process of converting from one lossy format to another, like from MP3
to Ogg Vorbis.
It is important to understand that although Ogg Vorbis is a better format than MP3,
transcoding never enhances sound quality. What has been lost in the initial MP3 com-
pression stage, will stay lost when converting to Ogg Vorbis, and there will always be
some additional quality loss. While the extra quality loss can be small enough that it
may be impossible to tell, the end result still is never better than the original file was.
If possible, it it recommended that users should avoid transcoding to avoid generation
loss. If transcoding is done (e.g. to get smaller files for a portable device), it is a good
idea to keep the original files.
For best results, compress Ogg Vorbis files from uncompressed sources, like CDs.
Rev. 1.70c 2012-11-16
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