The process of converting an audio or a video file from one format into another is called as encoding. Encoding serves a number of purposes for a DJ. We may encode files to decrease their size, to improve their quality or to simply make them easier to organize. Most formats allow tagging of tracks. Tagging is the process of adding information like the name of the artist, album etc. to the tracks. Encoding to lossless formats with an increased bit rate and resolution may even improve the quality of the source file, if performed properly. The actual encoding process for almost all the formats is mainly similar. I personally recommend Windows Media Audio 9 Series for all audio encoding purposes, but Ogg Vorbis and VQF are also good. A simple way to convert a wave file to WMA is explained here.
The first and foremost thing to do is to select a source file (duh!). Keep in mind that the source file must be of the highest quality possible. Do not encode previously encoded files as doing so can cause loss of quality. When encoding from a live source to file, be sure to configure the source at the highest quality possible. When encoding a file stored on your computer, be sure that it is of high quality. By high quality I mean having an appreciable bit rate. If you encode a 56 Kbps MP3 to a 128 Kbps WMA, you will not get a good result. It will only increase the file size and not the quality. However, if you do the opposite, i.e. convert a 128 Kbps MP3 to a 56 Kbps WMA, the resultant file will have a lesser file size without much loss of quality. Not much can be attained by encoding low quality files. Also remember that once a file is encoded to a lower quality, it cannot be reverted back. You cannot encode a file with a lower bit rate to a higher bit rate and increase the quality. In other words, you can downgrade quality with bit rate during an encoding session, but you cannot upgrade it. So always be sure about what you do to your files. Also, remember to back up your important files at all times, audio and otherwise. Some loss of quality always occurs when you convert a format into another. Exceptions to this rule are the lossless formats, but as mentioned earlier, their file size is comparatively larger. Let us take another example. If you convert a WMA file to an MP3 of the same bit rate, and then convert the MP3 back to a WMA, the result file would be of a lower quality than the one you started with. Don't get disheartened! This doesn't mean that encoding is bad. If you encode a file with specifications according to your need, you can get an accurate blend of quality and file size.
Ah! The age old question! Well, the answer to this one actually depends on what you are planning to do with the encoded media. This little specification is the most important one, and an incorrect bit rate may cause undesirable loss of quality. Also, while encoding to Windows Media, selection of an appropriate codec is also necessary. Since they both depend on what the encoded content is meant for, I'll explain both simultaneously.
Streaming
Viewing or listening to online content without downloading it to your computer is called as streaming. This media is stored on the server of a website and your media player plays it directly from it's location. Obviously, media files such as wave and .cda files cannot be directly streamed over the internet, considering the file size. It has to be converted to a more appropriate format before streaming. This is achieved by encoding it in a suitable format with an appropriate bit rate. The format to be used should have a good quality to compression ratio. In other words, it should compress the file to the maximum extent possible without much affecting the quality. Personally, I recommend Windows Media Audio 9 Series for streaming purposes. The Windows Media Audio 9 codec is appropriate for such encoding. Use CBR encoding for limiting the size of the file and a suitable bit rate. A mono recording is more clearly audible at lower bit rates than a stereo recording at the same bit rate. The appropriate bit rates for the various connection speeds are given below:
Dial up (28.8 Kbps)
Audio encoding mode: CBR
Audience: 11 Kbps
Audio codec: Windows Media Audio 9
Audio format: 8 kbps, 8 kHz, mono CBR
Dial up (56 Kbps)
Audio encoding mode: CBR
Audience: 24.01 Kbps
Audio codec: Windows Media Audio 9
Audio format: 20 kbps, 22 kHz, mono CBR
Archiving
If you have to store audio content on your computer, than file size is usually not an issue. In this case, there is no need for us to sacrifice quality. In this scenario I personally recommend Windows Media Audio 9 Professional Codec for encoding.
Codec: Windows Media Audio 9 Professional
VBR Quality 98, 44 kHz, 2 channel 24 bit 1-pass VBR
CD Burning
This is an area where both file size and quality have to be taken into consideration. The files should not take up too much size and should sound good as well. I suggest burning High Mat CD's rather than MP3's. But be aware that only limited hardware supports this format. So if you're planning to play these songs on a regular DVD player, go for MP3 format. In either case, a bit rate of 192 Kbps CBR should be appropriate. In case of WMA encoding, use the Professional codec.
Audio encoding is a pretty "heavy" process, i.e. it puts a drain on your CPU. So avoid doing anything else while encoding a track. The same goes for burning CD's as well.
Always use a bit rate suited to your requirement. This is usually gained through experience. Play around with the different formats and their settings until you find the right one for you.
Never re-encode previously encoded media. This will result in degraded quality.
Keep in mind that once a media has been downgraded by encoding, it cannot be upgraded. This means that if you have encoded a track to a low bit rate, you cannot re-encode it to a higher bit rate.
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