sgplay.1

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.\" Copyright (c) 1996 Entropic Research Laboratory, Inc.; All rights reserved
.\" @(#)sgplay.1	1.2 3/27/97 ERL
.ds ]W (c) 1996 Entropic Research Laboratory, Inc.
.TH SGPLAY 1\-ESPS 3/27/97
.SH NAME
sgplay - send sampled data (PCM) to native Indigo D/A converter.
.PP
.SH SYNOPSIS
.B sgplay
[
.BI \-r " range"
] [
.BI \-s " start time"
] [
.BI \-e " end time"
] [
.BI \-f " sample rate"
] [
.BI \-c " channel"
] [
.BI \-x " debug-level"
] [
.BI \-H
] [[
.BI \-i
]
.I file
] [
.I more-files
]
.PP
.SH DESCRIPTION
.PP
.I Sgplay
sends all or a portion of one or more ESPS, SIGnal, NIST or headerless
sampled data files to a Silicon Graphics Indigo digital-to-analog
converter.  A subrange of data within the files may be chosen; this
subrange may be specified in seconds or sample points.  Dual-channel
(stereo) or single-channel (monaural) data may be converted.
Single-channel input data may be directed to either or both output
channels.
.PP
Playback may be stopped by sending the terminal's interrupt character
(normally control-C) after playback has started.
.PP
If "\-" is given for a filename, then the input is taken from standard
input and must be an ESPS file or a headerless file (i.e., SIGnal or
NIST/Sphere files cannot be used with standard input).
.PP
The SGI Indigo program \fIapanel\fP may be used to set the output level, if desired.
\fIApanel\fP should be started before \fIsgplay\fP.
It may be left running indefinitely.
.PP
.SH OPTIONS
.PP
The following options are supported:
.TP
.BI \-r " range"
Select a subrange of points to be played, using the format
.I start\-end
,
.I start:end 
or
.IR start:+count .
Either the start or the end may be omitted; the beginning or the end of the
file are used if no alternative is specified. 
.IP
If multiple files were specified, the same range from each file is played.
.TP
.BI \-s " start time"
Specify the start time in seconds.  Play will continue to the end of file or
the end time specified with -e.  -s may not be used with -r.
.TP
.BI \-e " end time"
Specify the playback end time in seconds.  Play will start at the
beginning of file or the time specified by -s.  -e may not be used
with -r.
.TP
.BI \-f " frequency"
Specifies the sampling frequency.  The closest frequency to that
requested will be selected from those available and the user will be notified
if the selected value differs from that requested.  If -f is not
specified, the sampling frequency in the header is used, else
the default value for headerless files is 16kHz (assuming the standard Ariel crystal).
.TP
.BI \-c " channel"
Select the output channel configuration.  For files with headers, the
behavior is to play stereo if the file is stereo and to provide
identical output on both channels if the file is single-channel.
If the file has no header, the default is to assume single-channel
data and provide identical output to both channels.  For headerless
files, this may be changed with -\fIc\fP 2 (stereo data, stereo output).
.TP
.BI \-H
Force \fIsgplay\fP to treat the input as a headerless file.  This is probably unwise
to use unless the gain on your loudspeaker or earphones is way down, since
a file that really does have a header, or a file composed of data types other
than shorts (of the correct byte order!) will cause a terrible sound.
.TP
.BI \-i " input file"
Specify a file to be D/A converted.  Use of -i before the file designation is optional
if the filename is the last command-line component.  If no input file is
specified, or if "-" is specified, input is taken from stdin.
.TP
.BI \-x " debug_level"
Setting debug_level nonzero causes several messages to be printed as
internal processing proceeds.  The default is level 0, which causes no debug
output.
.PP
.SH "INTERACTION WITH XWAVES"
.I Sgplay
is designed to optionally use the server mode of \fIxwaves\fP (1\-\s-1ESPS\s+1).  This
is especially handy when
.I sgplay
is used as an \fIxwaves\fP external play
command (e.g. by setting the \fIxwaves\fP global play_prog).  When the latter is the case,
play commands initiated via \fIxwaves\fP' menu operations may be interrupted
by pressing the left mouse button in the data view.  \fIXwaves\fP will send
a signal (SIGUSR1) to the play program.  Sgplay responds to this
by sending back to \fIxwaves\fP a command "set da_location xx", where xx is
the sample that was being output when play was interrupted.  This
setting, in conjunction with \fIxwaves\fP' built-in callback procedure for
handling child-process exits, causes the \fIxwaves\fP signal display to
center itself on the sample where play was halted.
.PP
The SIGUSR1 signal to terminate 
.I sgplay
may come from any source.  If
it comes from sources other than \fIxwaves\fP, the environment variables
WAVES_PORT and WAVES_HOST must be correctly defined (see
\fIespsenv\fP (1-ESPS)), for correct functioning of the \fIxwaves\fP view
positioning.  (Of course, \fIxwaves\fP must actually be displaying the
signal in question at the time and \fIxwaves\fP must have initiated the
play.)
.PP
.I Sgplay
may also be interrupted with kill -2 (SIGINT) or kill -3
(SIGQUIT).  These signals are caught gracefully and 
.I sgplay
halts immediately, but no message is sent to \fIxwaves\fP.  No message is sent if
the play operation finishes without interruption.
.PP
.SH ESPS PARAMETERS
.PP
The parameter file is not read.  
.PP
.SH ESPS COMMON
.PP
ESPS Common is not read or written.
.PP
.SH DIAGNOSTICS
.PP
.I Sgplay
informs the user if the input file does not exist, if inconsistent
options are used, or if an unsupported sample rate is requested.
Also see \fBWARNINGS\fP below.
.PP
If the starting point requested is greater than the last point in the
file, then a message is printed.  If
the ending point requested is greater than the last point in the file,
it is reset to the last point and processing continues.
.PP
.SH WARNINGS
.PP
\fISgplay\fP supports only the "native" Indigo sampling rates.  These
are (in Hz): 48000 44100 32000 29400 24000 22050 16000 14700 12000
11025 10667 9800 9600 8820 8000 7350 6857 6400 6300 6000 5880 5512
5333 4900 4571 4200 4000 3675.  If you play a file that is sampled at
an unsupported rate, \fIsgplay\fP plays the data at the closest
supported rate and issues a warning.
.PP
\fISgplay\fP provides stereo D/A conversion at rates up to at least
48kHz when playing from local disk.  Sampling from network disks is
often feasible as well.  The maximum rate over the network is
unpredictable in general, but we routinely achieve 16kHz stereo at
Entropic Research Laboratory.  Of course rate limitations due to
network speed will be less severe for single-channel playing.
Obviously, processes supplying input to
.I sgplay
on a pipe must be able to keep up with the average aggregate sampling frequency.
.PP
.SH FILES
.PP
.SH BUGS
.PP
If readable header IS present, but -H is specified, the header is
treated like sampled data -- usually resulting in very unpleasant
sounds.
.PP
.SH SEE ALSO
.PP
.nf
SD(5\-\s-1ESPS\s+1), \fItestsd\fP(1\-\s-1ESPS\s+1), \fIcopysd\fP(1\-\s-1ESPS\s+1),
\fIsgrecord\fP(1\-\s-1ESPS\s+1), \fIsfconvert\fP(1\-\s-1ESPS\s+1), \fIsgram\fP(1\-\s-1ESPS\s+1),
\fIsend_xwaves2\fP(3\-\s-1ESPS\s+1)
.fi
.PP
.SH AUTHOR
.PP
David Talkin at Entropic Research Laboratory.