The bitrate is a measurement of the number of bits per time unit. This is usually in bits/second for MP3s/Video.
The greater the number of bits of data for a given second, the higher quality the MP3/video will be.
1 bit can have the value 0 or 1. Thus an MP3 with bitrate 1 bit/second could have sound on for 1 second, then sound off for another second. Most music is much more complex than on or off.
Increasing the number of bits used to encode the information allows many values to be stored, with greater resolution. For example 2 bits would allow 4 distinct values, 3 bits 8 distinct values - and so on. MP3's tend to be encoded at 128 or 192 Kilo bits per second (128 * 1024), whilst video tends to be in the range of Mega bits per second.
Understanding what the bitrate of an MP3 is, and the size of the MP3 file could tell you how long the song is.
File size = (bits/second * length of song(in seconds))/8 (for bytes)
Thus: length of song = (file size * 8) / bits/second
eg.
File = 3Mega Bytes (3 * 1024 * 1024)
Bitrate = 128 Kilo bits / second
Length in seconds = (3145728) / (128 * 1024)
= 192 seconds (just over 3 minutes).
Hope this helps
