sgrecord.1

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.\" Copyright (c) 1996 Entropic Research Laboratory, Inc.; All rights reserved
.\" @(#)sgrecord.1	1.2 3/28/97 ERL
.ds ]W (c) 1996 Entropic Research Laboratory, Inc.
.TH SGRECORD 1\-ESPS 3/28/97
.SH NAME
sgrecord - mono or stereo record to disk or pipe for native SGI Indigo A/D converter.
.PP
.SH SYNOPSIS
.B sgrecord
[
.BI \-s " duration"
] [
.BI \-f " sample rate"
] [
.BI \-c " channel"
] [
.BI \-S
] [
.BI \-W " xwaves display args."
] [
.BI \-P
] [
.BI \-p " prompt string"
] [
.BI \-x " debug-level"
] [
.BI \-H
] [[
.BI \-o
]
.I file
]
.PP
.SH DESCRIPTION
.PP
.PP
\fISgrecord\fP provides mono or stereo sampling at selected rates up to at least 48kHz when
recording to local disk.  Direct recording onto network disks is often
feasible as well.  Output files have ESPS FEA_SD headers, or,
optionally, no headers.  Output may optionally be directed to
\fIstdout\fP.  \fISgrecord\fP has special adaptations that permit tight
coupling with \fIxwaves\fP (see \fIINTERACTION WITH XWAVES\fP below).
.PP
When no output file is specified, \fIsgrecord\fP will, by default, write a FEA_SD file
to standard output.  When stereo recording
is selected (see the -c option) channels 0 and 1 alternate in the file, with
channel 0 being first.  Note that processes consuming the output of
\fIsgrecord\fP on a pipe must be able to keep up with the average aggregate
sampling frequency.  Options are available to control the sampling rate, recording duration, prompting, header suppression, and immediate display by \fIxwaves\fP.
.PP
The SGI Indigo program \fIapanel\fP may be used to monitor the input level(s),
set the input gain, and change the input source.  \fIApanel\fP should be started before
\fIsgrecord\fP.  It may be left running indefinitely.
.PP
.SH OPTIONS
.PP
The following options are supported:
.TP
.BI \-s " duration" "\fR [10]"
Specifies the maximum duration of the recording session in seconds.
Recording may be interrupted before this time expires with SIGINT,
SIGQUIT or SIGUSR1 (see below).  The default \fIduration\fP is 10 seconds.
The upper limit is set only by disk space.
.TP
.BI \-f " frequency" "\fR [16000]"
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 default sampling frequency of 16kHz is used (assuming the
standard Ariel crystal).
.TP
.BI \-c " channel" "\fR [1]"
By default sgrecord samples and stores single-channel data from the left channel.
Dual-channel (stereo) recording is selected by setting \fIchannel\fP to 2.
.TP
.BI \-S
Enable the \fIxwaves\fP(1\-ESPS) "make" command via \fIsend_xwaves2\fP(3\-ESPS) when the
requested recording time has elapsed or when recording is interrupted.  This 
permits immediate examination of the recorded passage using \fIxwaves\fP.  
See \fIINTERACTION WITH XWAVES\fP below.
.TP
.BI \-W
The argument to this option will be appended to the \fIsend_xwaves\fP
"make" command to permit display customization (e.g. via
window location and size specifications).  See \fIINTERACTION
WITH XWAVES\fP below.
.TP
.BI \-P
Enable a prompt message when A/D has actually commenced.  The default message
is a "bell ring" and the text "Start recording now ...."  This prompt may be changed
with the \-p option.
.TP
.BI \-p " prompt string"
\fIPrompt string\fP will be used as the alert that recording is commencing.  Specifying
\-p forces -P.
.TP
.BI \-H
Suppresses header creation.  A "bare" sample stream will result.  The default is
to produce an ESPS FEA_SD file with one or two channels depending on the
\-c option.
.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.
.TP
.BI -o " output"
Specifies a file for output.  Use of -\fIo\fP before the file designation is optional
if the filename is the last command-line component.  If no output file is
specified or if "-" is specified, output will go to \fIstdout\fP.
.PP
.SH "INTERACTION WITH XWAVES"
.PP
\fISgrecord\fP is designed to optionally use the server mode of \fIxwaves\fP(1\-ESPS) for
display of its output file on completion of the record operation.
This is implemented using \fIsend_xwaves2\fP(3\-ESPSu).  The following
conditions must be met for this feature to work.  (1) \fIXwaves\fP must be
running in the server mode. (2) The environment variables WAVES_PORT
and WAVES_HOST must be correctly defined (see \fIespsenv\fP(1\-ESPS)).  (3)
The record operation must be interrupted with a SIGUSR1 signal (e.g.
via "kill \-16 pid," where pid is the process ID of the \fIsgrecord\fP
process), or if \fIsgrecord\fP is not thus interrupted, the -\fIS\fP flag must have
been set.  (4) Output must be to a file.
.PP
An example \fImbuttons\fP(1\-ESPS) script to implement a primitive record
control panel follows:
.PP
.nf
.na
.ne 10
"RECORD Mono"  exec sgrecord  -P -s60 -S -W"name $$ loc_y 150" \\
                xx$$& echo $! > foo
"RECORD Stereo" exec sgrecord -P -c2 -s60 -S -W"name $$ loc_y 150" \\
                xx$$& echo $! > foo
"STOP"          kill -16 `cat foo`
"ERASE"         f=`cat foo` ; k=`echo $f 1 - p q | dc` ; \\
		kill -2 $f ; rm -f xx$k ; send_xwaves kill name $k
.fi
.ad
.PP
Note how the -\fIW\fP option is used to name the display ensemble and to fix
the vertical location of the waveform at the same place on consecutive
invocations.  In general, the -\fIW\fP option can be used to augment the
display generation as described under the "make" command in the \fIxwaves\fP
manual.  Note that the "STOP" function is implemented with a "kill
-16" (SIGUSR1).  This causes \fIsgrecord\fP to send the "make" command to
\fIxwaves\fP.  If either kill -2 (SIGINT) or kill -3 (SIGQUIT) is sent to
\fIsgrecord\fP, it will terminate gracefully, but will not send any messages
to \fIxwaves\fP.  The -\fIS\fP option causes the \fIxwaves\fP display operation to occur
even in the non-interrupted case (i.e. after 60 sec of recording).
The above script is not robust, but may serve as a useful starting
point for more serious attempts.
.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 WARNINGS
.PP
When output is to a file, the ESPS header, if it is present, will
correctly reflect the absolute maximum sample value encountered during
recording and the number of samples recorded.  If output is to a pipe,
these values are not recorded in the header.
.PP
If the output of \fIsgrecord\fP goes to the terminal, bad things will
happen to the terminal configuration and you may not be able to regain
control of the terminal.  In this case, kill the window or kill the
record process remotely from another window.
.PP
\fISgrecord\fP supports only the "native" SGI 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 an unsupported rate is
requested, \fIsgrecord\fP records at the closest supported rate and
issues a warning.
.PP
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 recording.
.PP
.SH FILES
.PP
.SH BUGS
.PP
If another \fIsgrecord\fP operation is started while one is in
progress, unpredictable results will occur.
.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),
\fIsgplay\fP(1\-\s-1ESPS\s+1), \fIsfconvert\fP(1\-\s-1ESPS\s+1), \fIsgram\fP(1\-\s-1ESPS\s+1)
.fi
.PP
.SH AUTHORS
.PP
David Talkin at Entropic Research Laboratory.