net/features.html; www.answers.com/topic/flac; http://en.wikipedia.org/wiki/ FLAC. 16 http://wiki.hydrogenaudio.org/index.php?title=Lossless_comparison; http://flac.sourceforge.net/ comparison.html www.compression-links.info/Lossless_Audio_Coding http://members.home.nl/w. speek/comparison.htm. 17 http://en.wikipedia.org/wiki/Lossy_data_compression. Overview of data compression standards Metadata MP3 frame ID3/APEv2 Header 4 bytes (418 bytes) Figure G2 MP3 frame sequence. analysis, 18 which capitalizes on the limitations of the human ear and the subjective perception and interpretation of sounds. For instance, sounds can obscure or mask each other in both time (forward or backward time masking) and frequency (frequency mask- ing). Also, weak sounds in the frequency spectrum may be masked by louder sounds at other frequencies. In all cases, the information concerning masked sounds can safely be removed without any audible loss of quality. The compression algorithm may also give priority to the sounds situated well within the audible range, which conveys an idea of the power of psychoacoustic modeling. Most lossy audio codecs, which include MP3, Ogg Vorbis, WMA, Musicam, LAME, and ATRAC, for instance, are based on such principles. The resulting compressed files typically represent 10-12% of the original audio recordings. Such an unparalleled feature opened new perspectives for broadcast- ing, downloading, and peer-to-peer sharing music over the Internet (overlooking, here, tricky issues of copyright, illegal copying, and piracy!), and in consumer electronics, such as portable music players. The key differences between these codecs are not only measured in compression and quality performance, or by their operating-system com- patibility, but also in the fact that they are either "proprietary," to be implemented under license, or alternatively offered as open-source programs, left to any manufacturer private user to implement freely or even to modify. As of today (2006), the patented and standardized MP3, 19 which app