Concentrating a little on lossy encoding formats, there are some options that we must consider before we continue to encode our audio files.
The bitrate is usually measured in 1000 bits per second or Kbps compression. The higher the bit rate, the higher the sound quality we will have but also, the larger the size of the resulting compressed audio file. Note that it is pointless to convert an audio file from a lower bitrate to a higher one higher (for example to convert a file from 128Kbps into a file of 256Kbps). The output file will still have the quality of the first file, i.e. 128kbps.
2) Lossy encoding options:
We have the following options when we are converting an audio stream to a lossy format:
Constant Bitrate (CBR): With this option, the same bit rate will be used to encode the entire audio file.
Variable Bitrate (VBR): VBR specifies the sound quality level but allows the bit rate to fluctuate. During complex passages, VBR uses a higher-than-average bit rate but during simple passages uses a lower-than-average bit rate. The result is that VBR produces an overall higher, more consistent sound quality compared to CBR at similar bit rates.
Average Bitrate (ABR): This is similar to VBR except that ABR is an encoding method that maintains the same bitrate across the entire audio file by regulating how variable the compression is.
3) Channel Selection:
Stereo: Two channels of audio, one for the left, and one for the right This is used to give the impression of space and movement.
Mono: One channel only. If you convert an audio stream with two channels into an audio stream with only one channel, both audio channels will be mixed together into a single track, using equal amounts from audio channels 1 and 2.
Joint Stereo: Joint stereo is the technique of encoding stereo audio into a "mid channel" which is a full channel average of the combined left and right channels, with a side channel which has separation information on how to re-create two distinct stereo signals. This can aid the compression ratio without having to lose valuable information from one of the audio channels.
Rate of measurement of samples per second. The higher the value, the better the sound quality will be. For example a CD stores samples at 44100Hz or 44.1KHz and a DAT tape stores samples at 48KHz.
When we use the normalize function in an audio file, we mean that we raise its volume so that the highest level sample in the file reaches a user defined level. This is used if for example we have a lot of audio files that don't have the same volume but we want to convert all of them so that perceptually they all sound equally loud.
6) ID3 Tags:
Audio tags are used to store metadata information about the audio file such as track name, author name, duration, release year, genre, etc. Tags are very useful for identifying tracks.
7) Compact Disc Database (CDDB):
CDDB is is a database where software applications can look up CD information over the Internet. This is performed by a client which calculates a (nearly) unique disc ID and then queries the database. As a result, the client is able to display the artist name, CD title, track list and some additional information. Usually you can find information only for original Compact Disks. Use this feature to save your tracks with all the information that is available without having to enter it by hand.