huffgen.1

speech signal process tools

.\" Copyright (c) 1987 Entropic Speech, Inc.; All rights reserved
.\" @(#)huffgen.1	1.2	8/13/87 ESI
.TH HUFFGEN 1\-ESPS 8/13/87
.ds ]W "\fI\s+4\ze\h'0.05'e\s-4\v'-0.4m'\fP\(*p\v'0.4m'\ Entropic Speech, Inc.
.ds ]Y "\fBESI INTERNAL\fP
.SH "NAME"
huffgen \- generate Huffman code tables from histogram arrays, for input to
the 2400 bps encoder.
.SH "SYNOPSIS"
.B huffgen
[
.BI \-h " hist_file"
]
.I " infile.fea outfile.fea"
.SH "DESCRIPTION"
.PP
\fIHuffgen\fR generates a set of Huffman code tables from the histogram arrays
in the FEA_QHIST file \fIinfile.fea\fR, and writes the results to the
expanded FEA_QHIST file \fIoutfile.fea\fR. The expanded file contains the
auxiliary record fields \fIcode\fR and \fIlength\fR. These give, respectively,
the numerical value and length (in bits) of the Huffman code word for each
element of the distribution corresponding to a particular histogram array.
For a more complete description of FEA_QHIST files and their extensions, see
\fIfea_qhist\fR (5\-ESPS) and \fIaux_qhist\fR (5\-ESPS).
.PP
The entropy and coding efficiency are computed for each input distribution,
and the results are written to a history file. The default name of this file
is \fIhuffgen.his\fR, but this can be overridden by the \fB\-h\fR option.
.PP
If \fIinfile.fea\fR is equal to "\-", standard input is used. If \fIoutfile.fea\fR
is equal to "\-", standard output is used.  
.SH OPTIONS
.TP
.BI \-h " hist_file"
Causes the statistical summaries for the various distributions to be placed
in the file \fIhist_file\fR, instead of in the default file, which is
\fIhuffgen.his\fR.
.SH "ESPS PARAMETERS"
.PP
The parameter file is not accessed by \fIhuffgen\fR.
.SH ESPS COMMON
.PP
ESPS Common is not used.
.SH ESPS HEADERS
.PP
The input FEA_QHIST file header is copied to the header of the expanded
FEA_QHIST output file. The input file header is added as a source in the
output file header, and the command line is added to the comment field.
.SH "FUTURE CHANGES"
.PP
A number of modifications to \fIhuffgen\fR will be required to complete the
design of the 2400 bps bitstream. Details are given in [1].
.SH WARNINGS
.PP
\fIHuffgen\fR issues a warning and exits if \fIinfile.fea\fR is not a
FEA_QHIST file.
.SH "SEE ALSO"
.PP
encode (1\-ESPS), histo (1\-ESPS), aux_qhist (5\-ESPS), fea_qhist (5\-ESPS).
.SH "BUGS"
.PP
No protection against overflow of the 32-bit code length is provided. In
practical situations with short tables (~32 words) and reasonable values
of the entropy (~4.0 or less), this should never present a problem.
.SH REFERENCES
.PP
[1] ETM-S-87-08:jpe, \fIRemaining Tasks in the 2400 bps Coding Development\fR,
Version 1.0, 07/13/87.
.SH "AUTHOR"
.PP
Program and manual page by Jim Elliott.