Re: combining mp3s
On Fri, Nov 26, 2004 at 04:37:17PM -0500, Michael Spang wrote:
} Patrick Wiseman wrote:
} >On Fri, 26 Nov 2004 16:02:29 -0500, Rick Pasotto <rick@niof.net> wrote:
} >>I have serveral mp3s that really should be a single file. What program
} >>should I use to combine them?
} >
} >I've had success with a simple 'cat file1.mp3 file2.mp3 > file3.mp3',
} >but I'm sure there's something wrong with that!
} >
} >Patrick
}
} Well.. considering many players can play uncompressed RAR files with a
} bunch of mp3s in them, it's not surprising that this works. Though
} certainly the result doesn't follow the mp3 standard; it won't have
} correct headers at the beginning and will have extra headers in the
} middle of the file.
The MPEG layer-III audio standard does not have any file headers or
footers. MP3 is, in fact, a streaming format and only individual frames
(which are essentially packets) have headers. As such, a file consisting of
a sequence of frames can be concatenated with another file consisting of a
sequence of frames and form a standards-compliant resulting stream.
In practice, however, many (most?) mp3 files have an IDv3 tag, which is a
file footer. If you concatenate a stream onto the end of a stream with such
a footer, that footer will be interpreted as garbage sitting between valid
frames and will be either silently ignored or played as garbled noise,
depending on the player and the details of the stream encoding.
For more information see:
http://www.id3.org/mp3frame.html
http://www.dv.co.yu/mpgscript/mpeghdr.htm
http://www.mp3-tech.org/programmer/frame_header.html
http://www.oreilly.com/catalog/mp3/chapter/ch02.html
} Michael Spang
--Greg
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