Music Video Codecs

In order to transmit, receive and replay audio-visual files you will need one of the many music video codecs available. The term 'codec' means COder/DECoder or COmpressor/DECompressor. Music video codecs are required to render data suitable for transmission using a set of protocols which must also be used for its reception. An example of a common music codec is MP3. Codecs can be supplied in the software, the hardware or in a combination of both. This article is about music codecs. Video signals will be discussed in another article.

When audio data is compressed, it results in a file smaller than the original. How much smaller depends on the type of codec, and data can be deliberately lost resulting in a reduction in audio quality. The type of music video codec where data is lost is called Lossy, while the other type where data is not lost is called Lossless.

The Lossless type of music video codecs work in much the same way as Zip files. Most people are acquainted with zip files, such as those requiring Acrobat to unzip them. In these, the data is compressed to take up less space. A zip file is actually a Lossless file codec: you use the zipping software to compress the data, then you subsequently require the zipping software to decompress it to a readable form. No data is lost, and this is how Lossless music video codecs work. They compress the data for transmission then decompress it to replay. The file is in exactly the same form when played as it was prior to transmission.

Examples of Lossless codecs are WavePack, Monkeys Audio and FLAK. This type of codec gives the best playback sound quality. Typical players are Winamp and Media Center. Since this type of file requires a Lossless codec for play-back, it will not play on an MP3 player. The main problem with Lossless music video codecs is that they compresses at best only to 4:1.

Where greater compression is required, Lossy codecs must be used. With these, part of the file data is lost or discarded to allow greater compression. It is not therefore fully a compression system: it is a file size reduction system with some compression added. Lossy music video codecs can reduce audio-video files sizes down to 10% of the original, which is a massive saving in storage requirements. The way it does this is to discards parts of the file it considers is not required by the human ear.

For example, the human ear cannot detect sound with a frequency higher than 16 KHz (Kilohertz) so the codecs cut out frequencies above this. Some codecs go down ever further to 12 KHz. Certain sound combinations are also discarded, such as soft sounds occurring immediately after harsh loud ones. The human brain normally will not distinguish these soft sounds from the loud one immediately preceding it, so they would not be missed if removed from the file. Once the codec decodes the audio file, it is not restored to the original size due to the loss of these components parts of the original file. Hence Lossy codec is more of a coder-decoder than compressor-decompressor. This is as true for music video codecs as it is for just the music codecs.

Examples of Lossy audio formats are MP3, OGG Vorbis, Musepack, MP4 and WMA (Windows Media Audio) . There are various codec encoders and decoders also available, though the average person generally has no choice since they are frequently installed in the hardware being used. A description of the software which carries out the encoding and decoding is beyond this article, but there are three main types: constant, variable and average bit-rate encoders. Higher bit-rates give better sound quality, but larger file sizes. Modern developments in both audio and video technology has revolutionized the way we buy music and movies due to a significant reduction in file downloading times. This is due to a combination of the developments in lossy music and video codecs and in internet connection bandwidths and bit-rates, but this is another subject which I shall deal with later.

An example of a music format which is not compressed at all is WAV. It takes up a lot of space and can take an age to download depending on your bit-rate or bandwidth. However, it is not widely known that WAV files can be compressed with any codec, including MP3. However, by far the most common format is pulse-code modulation (PCM) audio format. PCM WAV is an uncompressed, lossless storage method and gives the maximum audio quality - completely true to the original, unlike most music video codecs. You may have to download a specific music video codec occasionally to be able to open certain audio and video files you have either purchased or downloaded. If you have purchased the file, the codec will generally come with it, but with a free download you may also have to download the relevant codec. You may be informed what codec is needed to decode or decompress it. You should find the required codec on free download during an internet search.

The next article will discuss how music video codecs work with audio-video files and how their development has reduced the download time for movies to such an extent that downloading movies is now commonplace and proving a significant problem for the movie studios.

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