This is the libjpeg-turbo library.

libjpeg-turbo is a high-speed version of libjpeg for x86 and x86-64 processors
which uses SIMD instructions (MMX, SSE2, etc.) to accelerate baseline JPEG
compression and decompression.
libjpeg-turbo is generally 2-4x as fast as the unmodified version
of libjpeg, all else being equal.

libjpeg-turbo was originally based on libjpeg/SIMD by Miyasaka Masaru,
but the TigerVNC and VirtualGL projects made numerous enhancements to the codec,
including improved support for Mac OS X, 64-bit support,
support for 32-bit and big endian pixel formats (RGBA, ABGR, etc.),
accelerated Huffman encoding/decoding, and various bug fixes.
The goal was to produce a fully open source codec that could replace
the partially closed source TurboJPEG/IPP codec used by VirtualGL and TurboVNC.
libjpeg-turbo generally achieves 80-120% of the performance of TurboJPEG/IPP.
It is faster in some areas but slower in others.

WWW: http://libjpeg-turbo.virtualgl.org/