Digital Signal Processing Reference
In-Depth Information
MP2
MP3
Musepack (based on Musicam)
Ogg Vorbis (noted for its lack of patent restrictions)
WMA
Speech
CELP
G.711
G.726
Harmonic and Individual Lines and Noise (HILN)
AMR (used by GSM cell carriers, such as T-Mobile)
Speex (noted for its lack of patent restrictions)
Other data
Researchers have (semi-seriously) performed lossy compression on text by either using a
thesaurus to substitute short words for long ones, or generative text techniques , although
these sometimes fall into the related category of lossy data conversion.
Lowering resolution
A general kind of lossy compression is to lower the resolution of an image, as in image
scaling, particularly decimation. One may also remove less "lower information" parts of
an image, such as by seam carving.
Many media transforms, such as Gaussian blur, are, like lossy compression, irreversible:
the original signal cannot be reconstructed from the transformed signal. However, in
general these will have the same size as the original, and are not a form of compression.
Lowering resolution has practical uses, as the NASA New Horizons craft will transmit
thumbnails of its encounter with Pluto-Charon before it sends the higher resolution
images.