Compression artifact: Difference between revisions

Revision as of 05:55, 23 December 2004

Revision as of 05:57, 23 December 2004

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One technique is to use a lower sampling rate. Subtle details in the audio will be lost. The loss in quality will be uniform across the recording.

Another technique is to attempt to remove sounds that typical human hearing cannot perceive. As a human being cannot perceive the difference, the resulting data will be simpler (and thus compress better using loselesslossless techniques). For example, in general human beings are unable to perceive a quiet tone simultaneously with a similar, but louder tone. A lossy compression technique might identify this quiet tone and attempt to remove it. As no algorithm is perfect and tradeoffs can be made to throw away additional data to reduce data rate, this will occasionally lead to perceivable sounds being discarded. As these sounds are, ideally, hard to perceive anyway, the result will generally be of flattening complexity, or muddying the sound.

Many systems attempt to replace the series of samples of audio with other representations. Typically these representations make it easier to attempt to eliminate non-perceivable sounds and make it easier to compress the data using traditional lossless techniques. One common technique is to represent the audio as the sum of a series of sine waves. The representation may not be perfect; in exchange for a more easily compressed description, accuracy may be sacrificed.