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Mpc (Audio Compression Format)MPC, or Musepack, is a lossy audio compression format based on the MPEG-1 Layer-2 / MP2 algorithms, but heavily optimized and vastly improved in comparison. Unlike MPEG-1 Layer II, it uses: - subband-wise selectable M/S encoding (like MPEG-AAC)
- Huffman coding (like MPEG Layer III, MPEG AAC, ...)
- noise substitution techniques as used in ATSC A-52 and MPEG-4 AAC V2
- pure variable bitrate between 3 and 1300 kbit/s (when needed)
The psychoacoustic model of MPC is based on MPEG ISO model 2, but is extended by CVD (clear voice detection). The quantization algorithm of the MPC encoder performs spectral shaping of the noise, called adaptive noise shaping (ANS), in order to overcome the low frequency resolution of the polyphase quadrature filter bands. In May 2004, a series of listening tests (as reported on Slashdot) suggested that Musepack and Ogg Vorbis 1.1 (which was the "aoTuV" fork at the time) would be the two best available lossy codec for high-quality audio compression at bitrates around 128kbit/s, compared with MP3, AAC, WMA, or ATRAC. Other listening tests have also rated MPC highly. Listening tests of MPC: Development of MPC was initiated in 1997 by Andree Buschmann and later taken over by Frank Klemm, and is currently maintained by the Musepack Development Team (MDT) with assistance from Frank Klemm. Encoders and Decoders are available for Microsoft Windows, Linux and Mac OS X free of charge, mostly licensed as free software under the LGPL or BSD license. They are distributed via the MPC project's website (see external link below). Many third-party programs (audio players, CD rippers etc.) support MPC, either directly or via plugins. MPC uses the APEv2 tag metadata container. In the past, MPC has been under threat from multiple patents (MP2, PNS, subband) http://www.hydrogenaudio.org/forums/index.php?showtopic=6473. According to the developers of MPC, all patented code has been removed and it is now "patentless", but the official site doesn't provide any technical information beyond the mere claim. At least the PNS patent is still active, and it is not simple to know if MPC's own "noise substitution techniques" avoids its scope or not. This would probably require an official technical statement from the MPC team, if not a careful examination by a patent lawyer. External links
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