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author | Josh Coalson <jcoalson@users.sourceforce.net> | 2003-01-14 06:57:46 +0000 |
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committer | Josh Coalson <jcoalson@users.sourceforce.net> | 2003-01-14 06:57:46 +0000 |
commit | 83d275c43fe20bfe80ae56b78677e38f9f1aade4 (patch) | |
tree | b5043cf503888160fb6d2ec7cca5db113ec8a020 /doc/html/features.html | |
parent | 925438d8a31c958e57ad399ac8444dbf9d0f2168 (diff) | |
download | flac-83d275c43fe20bfe80ae56b78677e38f9f1aade4.tar.gz |
rewrite features verbiage
Diffstat (limited to 'doc/html/features.html')
-rw-r--r-- | doc/html/features.html | 53 |
1 files changed, 17 insertions, 36 deletions
diff --git a/doc/html/features.html b/doc/html/features.html index 36fb60d8..288db266 100644 --- a/doc/html/features.html +++ b/doc/html/features.html @@ -82,67 +82,48 @@ <P> <UL> <LI>the stream format</LI> - <LI><B><TT>libFLAC</TT></B>, a library of reference encoders and decoders, and a metadata interface</LI> - <LI><B><TT>libFLAC++</TT></B>, an object wrapper around libFLAC</LI> - <LI><B><TT>libOggFLAC</TT></B> and <B><TT>libOggFLAC++</TT></B>, which wrap the encoders and decoders of <TT>libFLAC</TT> and <TT>libFLAC++</TT>, respectively, to allow access to FLAC streams in an Ogg container</LI> - <LI><B><TT>flac</TT></B>, a command-line wrapper around <TT>libFLAC</TT> to encode and decode FLAC files</LI> - <LI><B><TT>metaflac</TT></B>, a command-line metadata editor for .flac files</LI> - <LI>input plugins for various music players (Winamp, XMMS, and more in the works)</LI> + <LI>reference encoders and decoders in library form</LI> + <LI><B><TT>flac</TT></B>, a command-line program to encode and decode FLAC files</LI> + <LI><B><TT>metaflac</TT></B>, a command-line metadata editor for FLAC files</LI> + <LI>input plugins for various music players</LI> </UL> </P> <P> - "Free" means that the specification of the stream format is in the public domain (the FLAC project reserves the right to set the FLAC specification and certify compliance), and that neither the FLAC format nor any of the implemented encoding/decoding methods are covered by any patent. It also means that the sources for the libraries are available under the <A HREF="http://www.opensource.org/licenses/lgpl-license.html">LGPL</A> and the sources for <B><TT>flac</TT></B>, <B><TT>metaflac</TT></B>, and the plugins are available under the <A HREF="http://www.opensource.org/licenses/gpl-license.html">GPL</A>. + "Free" means that the specification of the stream format is fully open to the public to be used for any purpose (the FLAC project reserves the right to set the FLAC specification and certify compliance), and that neither the FLAC format nor any of the implemented encoding/decoding methods are covered by any known patent. It also means that all the source code is available under open-source licenses. </P> <P> FLAC compiles on many platforms: most Unixes (Linux, *BSD, Solaris, OS X), Windows, BeOS, and OS/2. There are build systems for autoconf/automake, MSVC, Watcom C, and Project Builder. </P> <P> - What FLAC is: + Notable features of FLAC: </P> <UL> <P><LI> - FLAC is patent free. The FLAC format or encoding/decoding methods are not covered by any patents. + <B>Lossless</B>: The encoding of PCM data incurs no loss of information, and the decoded audio is bit-for-bit identical to what went into the encoder. Each frame contains a 16-bit CRC of the frame data for detecting transmission errors. The integrity of the audio data is further insured by storing an <A HREF="http://userpages.umbc.edu/~mabzug1/cs/md5/md5.html">MD5 signature</A> of the original unencoded audio data in the file header, which can be compared against later during decoding or testing. </LI></P> <P><LI> - FLAC is lossless. The encoding of PCM data incurs no loss of information, and the decoded audio is bit-for-bit identical to what went into the encoder. Each frame contains a 16-bit CRC of the frame data for detecting transmission errors. The integrity of the audio data is further insured by storing an <A HREF="http://userpages.umbc.edu/~mabzug1/cs/md5/md5.html">MD5 signature</A> of the original unencoded audio data in the file header, which can be compared against later during decoding or testing. + <B>Fast</B>: FLAC is asymmetric in favor of decode speed. Decoding requires only integer arithmetic, and is much less compute-intensive than for most perceptual codecs. Real-time decode performance is easily achievable on even modest hardware. </LI></P> <P><LI> - FLAC is designed to compress audio data. Technically, <B><TT>flac</TT></B> can "compress" other kinds of data losslessly (if you pass it in as a mono 8-bit raw file), but the output files tend to be bigger. + <B>Hardware support</B>: Because of FLAC's free reference implementation and low decoding complexity, FLAC is currently the only lossless codec that has any kind of hardware support. </LI></P> <P><LI> - The compression capabilities of FLAC are extendable, meaning that new methods can be added to future versions of the format without breaking older streams or decoders. + <B>Streamable</B>: Each FLAC frame contains enough data to decode that frame. FLAC does not even rely on previous or following frames. FLAC uses sync codes and CRCs (similar to MPEG and other formats), which, along with framing, allow decoders to pick up in the middle of a stream with a minimum of delay. </LI></P> <P><LI> - The currently implemented compression methods in the reference encoder yield streams smaller than shorten. The encoding time is variable, but is generally between that of <A HREF="http://www.softsound.com/Shorten.html">shorten</A>, and that of, say, <A HREF="http://www.mp3dev.org/mp3/">LAME</A>. The most aggressive compression however can be quite slow. For more info see the <A HREF="comparison.html">comparison page</A>. + <B>Seekable</B>: FLAC supports fast sample-accurate seeking. Not only is this useful for playback, it makes FLAC files suitable for use in editing applications. </LI></P> <P><LI> - FLAC is asymmetric in favor of decode speed. Decoding requires only integer arithmetic, and is much less compute-intensive than for most perceptual codecs. Real-time decode performance is easily achievable on even modest hardare. + <B>Flexible metadata</B>: New metadata blocks can be defined and implemented in future versions of FLAC without breaking older streams or decoders. Currently there are metadata types for tags, cue sheets, and seek tables. Applications can write their own <A HREF="format.html#def_APPLICATION">APPLICATION</A> metadata once they <A HREF="id.html">register an ID</A> </LI></P> <P><LI> - FLAC is suitable for archiving, since there is no information loss. You are not locked into the format since there is no generation loss if you decide to convert your data to another format in the future. In addition to the frame CRCs and MD5 signature, <B><TT>flac</TT></B> has a verify option that decodes the encoded stream in parallel with the encoding process and compares the result to the original, aborting with an error if there is a mismatch. + <B>Suitable for archiving</B>: FLAC is an open format, and there is no generation loss if you need to convert your data to another format in the future. In addition to the frame CRCs and MD5 signature, <B><TT>flac</TT></B> has a verify option that decodes the encoded stream in parallel with the encoding process and compares the result to the original, aborting with an error if there is a mismatch. </LI></P> <P><LI> - FLAC is suitable for streaming. Each FLAC frame contains enough data to decode that frame. FLAC does not even rely on previous or following frames. FLAC uses sync codes and CRCs (similar to MPEG and other formats), which, along with framing, allow decoders to pick up in the middle of a stream with a minimum of delay. + <B>Convenient CD archiving</B>: FLAC has a metadata block for storing a CD table of contents and all track and index points. For instance, you can rip a CD to a single file, then import the CD's extracted cue sheet while encoding to yield a single file representation of the entire CD. If your original CD is damaged, the cue sheet can be exported later in order to burn an exact copy. </LI></P> <P><LI> - FLAC supports fast sample-accurate seeking. Not only is this useful for playback, it makes FLAC files suitable for use in editing applications. - </LI></P> - <P><LI> - FLAC has an extendable metadata system. New metadata blocks can be defined and implemented in future versions of FLAC without breaking older streams or decoders. Applications can write their own <A HREF="format.html#def_APPLICATION">APPLICATION</A> metadata once they <A HREF="id.html">register an ID</A>. ID3 and ID3V2 tags may be attached to .flac files without disrupting the decoder. - </LI></P> - </UL> - <P> - Some things that follow from the features: - </P> - <UL> - <P><LI> - FLAC streams can be played back consecutively with no audible gaps in between, unlike say, MP3s (this is one of the minor <A HREF="goals.html">goals</A>). For example, you can encode a live album as individual tracks and still play them back seamlessly. - </LI></P> - <P><LI> - The sample-accurate seeking allows versatile playback: a sophisticated player could do index points, complex looping, or other structured playback. This could be useful in for say DJs, or practice sessions where you want to play along through specific passages. - </LI></P> - <P><LI> - Basically, you get the versatility of a WAV file in a compressed streamable format. + <B>Error resistant</B>: Because of FLAC's framing, stream errors limit the damage to the frame in which the error occurred, typically a small fraction of a second worth of data. Contrast this with some other lossless codecs, in which a single error destroys the remainder of the stream. </LI></P> </UL> <P> @@ -150,10 +131,10 @@ </P> <UL> <P><LI> - Lossy. FLAC is intended for lossless compression only, as there are many good lossy formats already, such as <A HREF="http://www.mp3-tech.org/">MP3</A> (see <A HREF="http://www.mp3dev.org/mp3/">LAME</A> for an excellent open-source implementation), and <A HREF="http://www.xiph.org/ogg/vorbis/index.html">Ogg Vorbis</A>. + Lossy. FLAC is intended for lossless compression only, as there are many good lossy formats already, such as <A HREF="http://www.xiph.org/ogg/vorbis/index.html">Vorbis</A>, <A HREF="http://musepack.org/">MPC</A>, and <A HREF="http://www.mp3-tech.org/">MP3</A> (see <A HREF="http://www.mp3dev.org/mp3/">LAME</A> for an excellent open-source implementation). </LI></P> <P><LI> - SDMI compliant, et cetera. There is no intention to support any methods of copy protection, which are, for all practical purposes, a complete waste of bits. (Another way to look at it is that since copy protection is futile, it really carries no information, so you might say FLAC already losslessly compresses all possible copy protection information down to zero bits!) Of course, we can't stop what some misguided person does with proprietary meta-data blocks, but then again, non-proprietary decoders will skip them anyway. + SDMI compliant, et cetera. There is no intention to support any methods of copy protection, which are, for all practical purposes, a complete waste of bits. (Another way to look at it is that since copy protection is futile, it really carries no information, so you might say FLAC already losslessly compresses all possible copy protection information down to zero bits!) Of course, we can't stop what some misguided person does with proprietary metadata blocks, but then again, non-proprietary decoders will skip them anyway. </LI></P> </UL> </FONT> |