Transparency (data compression)

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In data compression and psychoacoustics, transparency is the result of lossy data compression accurate enough that the compressed result is perceptually indistinguishable from the uncompressed input, i.e. perceptually lossless.

A transparency threshold is a given value at which transparency is reached. It is commonly used to describe compressed data bitrates. For example, the transparency threshold for MP3 to linear PCM audio is said to be between 175 and 245 kbit/s, at 44.1 kHz, when encoded as VBR MP3 (corresponding to the -V3 and -V0 settings of the highly popular LAME MP3 encoder).^[1] This means that when an MP3 that was encoded at those bitrates is being played back, it is indistinguishable from the original PCM, and the compression is transparent to the listener.

The term transparent compression can also refer to a filesystem feature that allows compressed files to be read and written just like regular ones. In this case, the compressor is typically a general-purpose lossless compressor.