gaintool - audio control panel

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SYNOPSIS

DISCLAIMER

This program is furnished on an AS IS basis as a demonstration of audio applications programming.

DESCRIPTION

gaintool demonstrates an important principle involved in the integration of audio in the desktop environment: by enabling global control of important audio characteristics, it is not necessary for every application to provide an interface for these parameters. For instance, since audio output may be paused from the control panel, it is not strictly necessary that output applications display a Pause button of their own. However, such applications may detect that audio output has been paused, and take appropriate action.

Control Panel

Play Volume

This slider adjusts the output volume. Volume levels between 0 and 100 may be selected, where 0 represents infinite attenuation and 100 is maximum gain.

Record Volume

This slider adjusts the recording gain level in the range 0 to 100.

Monitor Volume

Monitor gain controls the amount of audio input signal that is fed through to the output port. For instance, if an audio source (such as a radio or CD-player) is connected directly to the input port, the input signal may be monitored through either the built-in speaker or the headphone jack by adjusting this slider. Note that there may be audible feedback (a high-pitched whine) if a microphone is connected to the workstation and the monitor volume is set greater than zero.

Output

This selector switches the audio output port between the built-in speaker and the external headphone jack.

Pause Play

This button may be used to suspend and resume audio output. If audio output is in progress when Pause is pressed, it is stopped immediately and subsequent output data remains queued. The button then switches to a Resume button that, when pressed, resumes audio output at the point that it was suspended.

If no process has the device open for output when Pause is pressed, gaintool holds the device open itself, thereby denying other processes output access. Audio programs that simply open and write to the audio device will typically be suspended when they attempt to open the device. Programs that asynchronously poll the device will discover that it is ``busy'' and may take appropriate action.

Audio Device Status Panel

gaintool also includes an audio status panel that shows the current state of the audio device. This panel is extremely useful for debugging audio applications. Selecting ``Status...'' from the panel menu brings up the status panel (this can also be done on a SPARC system by pressing the PROPS (L3) key). Selecting ``Done'' from the panel menu removes the panel (this can also be done on a SPARC system by pressing the OPEN (L7) key).

When the Update Mode is set to Status Change, the audio device status is updated only when a SIGPOLL signal is delivered to gaintool (see audio.7i on an x86 system see sbpro.7d Because of this, the Active and Samples indicators are not necessarily kept up-to-date. This mode is useful for application debugging in order to see exactly when audio device status changes are being reported. When the Continuous mode is selected, the status is continually updated.

SEE ALSO

See audiotool manual page in

SPARC Only

x86 Only

Created by unroff & hp-tools. © by Hans-Peter Bischof. All Rights Reserved (1997).

Last modified 07/October/97