toast -- GSM 06.10 lossy sound compression
SYNOPSIS
toast [ -cdfpvhualsFC ] [ filename... ]
untoast [ -cfpvhuaslF ] [ filename... ]
tcat [ -vhuaslF ] [ filename... ]
DESCRIPTION
Toast compresses the sound files given on its command
line. Each file is replaced by a file with the extension
.gsm . If no files are specified, the compression is
applied to the standard input, and its result is written
to standard output.
Toasted files can be restored to something not quite
unlike their original form by running toast -d , or
untoast , on the .gsm-files or standard input.
The program tcat (the same as running untoast -c ) uncom
presses its input on standard output, but leaves the com
pressed .gsm-files alone.
When files are compressed or uncompressed into other
files, the ownership (if run by root), modes, accessed and
modified times are maintained between both versions.
OPTIONS
-c (cat) Write to the standard output; no files are
changed.
-d (decode) Decode, rather than encode, the files.
-f (force) Force replacement of output files if they
exist. If -f is omitted and toast (or untoast) is
run interactively from a terminal, the user is
prompted as to whether the file should be replaced.
-p (precious) Do not delete the source files. Source
files are implicitly left alone whenever -c is
specified or tcat is run.
-C (LTP cut-off) Ignore most sample values when calcu
lating the GSM long-term correlation lag during
encoding. (The multiplications that do this are a
bottleneck of the algorithm.) The resulting encod
ing process will not produce exactly the same
results as GSM 06.10 would, but remains close
enough to be compatible.
The -C option applies only to the encoder and is
silently ignored by the decoder.
but without a multiplication instruction, -F sacri
fices standard conformance to performance and
nearly doubles the speed of the algorithm.
The resulting encoding and decoding process will
not produce exactly the same results as GSM 06.10
would, but remains close enough to be compatible.
The default is standard-conforming operation.
-v (version) outputs the version of toast (or untoast
or tcat) to stdout and exits.
-h (help) prints a short overview of the options.
Toast, untoast and tcat try to guess the appropriate audio
data format from the file suffix. Command line options
can also specify a format to be used for all files.
The following formats are supported:
-u (µU-law) 8 kHz, 8 bit µU-law encoding (file suffix
.u)
-a (A-law) 8 kHz, 8 bit A-law encoding (file suffix
.A)
-s (Sun audio) 8 kHz, 8 bit µU-law encoding with audio
header (file suffix .au)
-l (linear) 8 kHz, 16 bit signed linear encoding in
host byte order with 13 significant bits (file suf
fix .l)
In absence of options or suffixes to specify a format, µU-
law encoding as forced by -u is assumed.
PECULIARITIES
A four bit magic number is prefixed to each 32 1/2-byte
GSM frame, mainly because 32 1/2-bytes are rather clumsy
to handle.
WARNING
The compression algorithm used is a lossy compression
algorithm devised especially for speech; on no account
should it be used for text, pictures or any other non-
speech-data you consider valuable.
BUGS
Please direct bug reports to jutta@cs.tu-berlin.de.
SEE ALSO
gsm(3)
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