apass(1) apass(1)
NAME
apass - copy from one AF server to another
SYNOPSIS
apass [-ia input-AF-server] [-oa output-AF-server] [-full_duplex] [-id
input-device-#] [-od output-device-#] [-delay seconds] [-aj anti-jitter-
seconds] [-buffering buffering-seconds] [-g dB-gain] [-e encodingType]
[-log] [-f <parameter-file>]
DDESCRIPTION
apass reads samples from the input audio server and writes them to the out-
put audio server. There will be delay seconds between input and output.
OPTIONS
-ia server
Specifies which audio server to record the sound from. Defaults to
the value of the AUDIOFILE environment variable.
-oa server
Specifies which audio server to play the sound to. Defaults to the
value of the AUDIOFILE environment variable.
-full_duplex
Copies sound in both directions (between input and output servers.)
-id device
Specifies which audio device on the input server to record the sound
from. Defaults to the first device that isn't connected to the tele-
phone, which is often the local microphone device.
-od device
Specifies which audio device on the output server to play the sound
to. Defaults to the first device that isn't connected to the tele-
phone, which is often the local speaker device.
-delay seconds
Sets the record to playback delay. The default value is 0.2 seconds.
This delay is made up of three components, the buffer size - because
you cannot play back a sample until the whole buffer is recorded, the
nominal anti-jitter delay, which absorbs variation in the scheduling
and transport delays between the record server and the playback
server, and a pure delay. The minimum value is buffering+aj and the
maximum is 3.0 seconds.
-aj seconds
Sets the tolerance for clock drift between the input and the output.
If the input to output delay drifts from its nominal value by more
than this amount, the delay will be resynchronized, probably resulting
in an audible blip. Default value is 0.1 seconds. Legal values are 0
to 1 second.
-buffering seconds
This parameter sets the amount of audio read from the input and writ-
ten to the output as a single operation. It sets a minimum value for
delay. The default value is 0.2 seconds. Legal values are 0.1 to 0.5
second.
-g dB-gain
Controls the playback gain. The default value is 0 dB. Legal values
are from -30 to +30.
-e encodingType
Sets the encoding type of the audio. This information is passed to
the sending and receiving AF servers, where any necessary conversions
will be done. "-e xxx" will get a list of acceptable types. Some
types may not be supported by some servers. If the -e switch is not
specified, the encoding type will be the natural type of the input AF
device.
-log
If set, apass will print a message on stdout whenever it is necessary
to resynchronize clocks between input and output and whenever the
record side of the program takes longer than 400 milliseconds.
-f file
Whenever a SIGUSR1 is received, apass will read file to acquire param-
eters. The parameter file should contain one or more lines. Each
value should have a keyword and a value. Legal keywords are delay,
buffering, aj, and gain.
A typical parameter file might contain:
delay 0.3
buffering 0.2
aj 0.1
gain 0.0
The general idea behind the -f file feature is that another process
can be used to control the apass process. For example, a tk(1) pro-
gram or emacs keybindings could alter the behavior of apass. This
permits a multi-process but single threaded environment to act like a
multi-threaded environment.
ENVIRONMENT
AUDIOFILE specifies the host and server to use if otherwise unspeci-
fied
BUGS
must be some
If you encounter a reproducible bug, please submit a problem report to
(af-bugs@crl.dec.com).
SEE ALSO
AF(1), aplay(1)
COPYRIGHT
Copyright 1993-1994, Digital Equipment Corporation.
See AF(1) for a full statement of rights and permissions.
AUTHORS
Digital Cambridge Research Lab