BIT RATE
The bit rate of an MP3 indicates the density of the audio information contained in the file. Therefore, every second on a 192 kbps MP3 contains 192 kilobits (24 bytes) of data. The higher the bit rate, the more information the MP3 contains; The more information it contains, the quality will be closer to the original audio recording. The bit rate also determines the size of the MP3 file: a four-minute song encoded at 128 kbps takes up just over 3.5 MB, while the same song encoded at 320 kbps requires more than 9 MB of space.
CHOOSE A BIT RATE
When converting an audio file or ripping the CD collection to MP3, you must specify the bit rate you want the encoder to use. Choose a bit rate based on the type of audio you are encoding and the desired purpose. If you are converting a conference or other piece of vocal audio, a 128 kbps bit rate is more than enough. If you encode MP3 files for use with a portable media player, a 192 kbp bitrate generally provides a good balance between audio quality and file size. If you are converting your CD collection to MP3 for archiving, encode your files with 320kbps bit rate.
VARIABLE BIT SPEED
Encoding with a variable bit rate changes the MP3 bit rate based on the type of data present at a certain point in the audio. For example, a variable bit rate encoder can encode dense information from an MP3 at 320 kbps; however, when the audio contains a mute section, the encoder reduces the bit rate to 32 kbps. If the bit rate of an MP3 has an unusual number (for example 204 kbps), this indicates that the MP3 creator has encoded it with a variable bit rate.
BITS SPEED CONVERSION
Although most MP3 encoding and conversion programs can modify an MP3 with a different bit rate, this is not a good idea in general. Converting an MP3 to a higher bit rate does not add audio information to the file, so the sound quality does not increase. Converting an MP3 to a lower bit rate reduces the file size, but it could also have audio defects as the encoder is compressing an already compressed file. If you need an MP3 file to have a different bit rate, re-encode an MP3 from the original audio CD or WAV file.
