Variable bitrate: With a variable bitrate, the audio
file is not encoded with a specified, constant bitrate
but the encoding depends on the individual
elements of the audio file instead. Complex
elements are compressed less than simple ones, so
that the result is an mp3PRO file that depending on
the desired quality offers the best possible, loss-free
result. The medium quality has proved itself to be a
fairly good compromise between sound quality and
file size. At this bitrate, audio files, very roughly
speaking, are compressed by somewhat more than
a factor of 20. This means that a normal track of
around three to four minutes in length (in CD quality;
in other words 44.1 kHz, 16 Bit, stereo) can be
compressed to a 1.5 - 2 megabyte MP3 file by these
means.
Once you are satisfied with the settings, click on the
'OK' button to close the dialog or make additional
alterations to the expert settings.
Expert settings
If you click on the 'Expert' button, the dialog will be
extended, allowing special options to be chosen that
are not relevant to the 'normal' user.
Original bit: This means that the mp3PRO file is an
original and not a copy. This information can be
important in relation to future copy protection options
and is also of value to the user for information
purposes.
Private bit: The user can set this bit however he or
she wants. It has been conceived primarily for those
users who want to decode or evaluate mp3PRO
files. The bit is stored in the mp3PRO file, but nearly
all programs ignore it.
Copyright bit: This bit means that the mp3PRO file
concerned is copyright-protected. In addition, it is
used for SCMS (Serial Copy Management System).
However, it does not have (or at least currently does
not have) any influence when playing or burning the
files.
Write CRC: By setting this bit, checksums (proof
totals) are also stored. These recognize defective
sections of the file (which may have arisen from
incorrect data transfer from the Internet, etc.).
However, many decoders ignore this checksum
information, while others reproduce a defective
mp3PRO section as silence, in order to avoid sound
interference in a defective part of the file. The
mp3PRO file will be very slightly larger if this option
is chosen.
Allow intensity stereo coding: Setting this option
permits the use of a special type of that only saves
directional information and volume for high
frequencies. This option should normally be
activated.