157 lines
3.8 KiB
Groff
157 lines
3.8 KiB
Groff
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.\"
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.\" Copyright 1992 by Jutta Degener and Carsten Bormann, Technische
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.\" Universitaet Berlin. See the accompanying file "COPYRIGHT" for
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.\" details. THERE IS ABSOLUTELY NO WARRANTY FOR THIS SOFTWARE.
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.\"
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.if n .ds mU u
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.if t .ds mU \(*m
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.\"
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.TH TOAST 1 local
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.SH NAME
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toast \(em GSM\ 06.10 lossy sound compression
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.SH SYNOPSIS
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.ll +8
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.B toast
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[
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.B \-cdfpvhualsFC
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] [
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.I "filename...\&"
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]
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.LP
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.B untoast
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[
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.B \-cfpvhuaslF
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] [
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.I "filename...\&"
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]
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.LP
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.B tcat
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[
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.B \-vhuaslF
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] [
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.I "filename...\&"
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]
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.ll -8
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.SH DESCRIPTION
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Toast compresses the sound files given on its command line.
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Each file is replaced by a file with the extension
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.I \&.gsm .
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If no files are specified, the compression is applied to the
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standard input, and its result is written to standard output.
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.PP
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Toasted files can be restored to something not quite unlike
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their original form by running toast
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.I "\-d"
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, or
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.I untoast
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, on the \&.gsm-files or standard input.
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.PP
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The program
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.I tcat
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(the same as running
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.I "untoast \-c"
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) uncompresses its input on standard output,
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but leaves the compressed .gsm\-files alone.
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.PP
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When files are compressed or uncompressed into other files,
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the ownership (if run by root), modes, accessed and modified times
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are maintained between both versions.
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.SH OPTIONS
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.TP
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.B \-c
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(cat)
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Write to the standard output; no files are changed.
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.TP
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.B \-d
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(decode)
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Decode, rather than encode, the files.
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.TP
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.B \-f
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(force)
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Force replacement of output files if they exist.
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If \-f is omitted and toast (or untoast) is run interactively from
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a terminal, the user is prompted as to whether the file should be replaced.
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.TP
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.B \-p
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(precious)
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Do not delete the source files.
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Source files are implicitly left alone whenever \-c is
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specified or tcat is run.
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.TP
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.B \-C
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(LTP cut-off)
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Ignore most sample values when calculating the GSM long-term
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correlation lag during encoding.
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(The multiplications that do this are a bottleneck
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of the algorithm.)
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The resulting encoding process will not produce
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exactly the same results as GSM 06.10 would,
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but remains close enough to be compatible.
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.br
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The
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.B \-C
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option applies only to the encoder and is silently
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ignored by the decoder.
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.TP
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.B \-F
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(fast)
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On systems with a floating point processor, but without
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a multiplication instruction, \-F sacrifices standard conformance to
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performance and nearly doubles the speed of the algorithm.
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.br
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The resulting encoding and decoding process will not produce
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exactly the same results as GSM 06.10 would, but remains close
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enough to be compatible.
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.br
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The default is standard-conforming operation.
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.TP
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.B \-v
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(version)\
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outputs the version of toast (or untoast or tcat) to stdout and exits.
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.TP
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.B \-h
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(help)\
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prints a short overview of the options.
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.PP
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Toast, untoast and tcat try to guess the appropriate audio data
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format from the file suffix.
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Command line options can also specify a format to be used for
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all files.
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.br
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The following formats are supported:
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.TP
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.B "\-u"
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(\(*mU-law)
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8 kHz, 8 bit \(*mU-law encoding (file suffix .u)
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.TP
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.B "\-a"
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(A-law)
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8 kHz, 8 bit A-law encoding (file suffix .A)
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.TP
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.B "\-s"
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(Sun audio)
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8 kHz, 8 bit \(*mU-law encoding with audio header (file suffix .au)
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.TP
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.B "-l"
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(linear)
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8 kHz, 16 bit signed linear encoding in host byte order
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with 13 significant bits (file suffix .l)
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.PP
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In absence of options or suffixes to specify a format,
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\(*mU-law encoding as forced by \-u is assumed.
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.PP
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.SH PECULIARITIES
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A four bit magic number is prefixed to each 32 1/2-byte GSM frame,
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mainly because 32 1/2-bytes are rather clumsy to handle.
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.SH WARNING
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The compression algorithm used is a lossy compression algorithm
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devised especially for speech; on no account should it be used
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for text, pictures or any other non-speech-data you consider
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valuable.
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.SH BUGS
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Please direct bug reports to jutta@cs.tu-berlin.de.
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.SH "SEE ALSO"
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gsm(3)
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.\"
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.\" Toast is dedicated to Bill Sienkiewicz, author of "Stray Toasters".
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