mp3 coding
- 2008-10-04 00:21:55
MP3 File Compression Techniques
Perceptual Coding Techniques
Minimum Audio Threshold: This is the non-linear lower level limit of human hearing. Audio content below this curve not perceived is not coded.
Masking Effect: Strong sounds mask (hide) weaker sounds. Sound too weak to be perceived are not coded.
Intensity Stereo Coding: Some frequencies are often difficult to determine location (Low-frequency bass sounds for example) These frequencies are coded as monophonic with additional information to restore the perception of the soundstage.
Mid/Side Stereo Coding: When the left and the right channels are quite similar, a middle (L+R) and a side (L-R) channels are encoded instead of left and right. This reduces the final file size by using less bits for the side channel.
Intuitive Coding Techniques
Bytes reservoir: MP3 coding uses then a short reservoir of bytes that acts as a buffer by borrowing capacity from passages that can be coded to an inferior rate without sonic degradation
Huffman Coding: Uses shorter codes to replace repetitive bytes (simple pure tones) in audio signal. Can save up to 20% in file size
