NAME
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 ) uncompresses its
input on standard output, but leaves the compressed .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 calculating the GSM
long-term correlation lag during encoding. (The multiplications
that do this are a bottleneck of the algorithm.) The resulting
encoding 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.
-F (fast) On systems with a floating point processor, but without a
multiplication instruction, -F sacrifices 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 suffix .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)
local TOAST(1)