Lossy compression
Lossy compression definition
Lossy compression is a compression in which some information in the original information sequence is lost. This means that once the original information is manipulated by the lossy compression process, it cannot be obtained by the generated sequence by reducing it again. Lossy compression usually removes some redundant information and details in order to achieve higher compression ratios, and the loss of this information does not affect the quality of human perception.
Application Scenarios of Lossy Compression
Lossy compression is widely used to compress voice, image and video data. For example, JPEG format is a typical lossy compression format commonly used in image compression to effectively reduce file size by reducing color depth and resolution. Lossy compression formats include MP3, DivX, Xvid, JPEG, RM, RMVB, WMA, WMV, etc.
The lossy and lossless compression coding frameworks are roughly the same. Firstly, the spatial domain representation is transformed into a frequency domain representation by using the discrete cosine transform, and then the DCT coefficients are quantized by using a weighting function that is optimal for the human visual system. Decoding, or decompression, is the reverse of the compression encoding process.
Compared with lossless compression, lossy compression loses some information, and the lost information cannot be recovered. Lossy compression mainly sacrifices the high-frequency components in the audio. Lossy compression ensures a high compression ratio at the cost of losing some information. And the human ear is not sensitive to high-frequency sound, after a certain frequency can not hear at all. The MP3 format is the most common form of lossy compression. In the case of MP3, most of the loss in lossy compression occurs at high frequencies. Lossy audio in other formats is generally similar, except that the compression algorithm may be more sophisticated, and the high-frequency components may not be lost as much as in MP3 formats.
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