class Listen : public DatEnv

Listen to a data channel
The Listen monitor plays a data channel in real-time over the speakers on the default audio device of a DMT workstation. At present a single channel is played. The channel data are resampled to 8kHz by linear interpolation to match the usual sampling rate for audio output devices. Optional high pass and low-pass filters may be applied to the data before the data are sent to the audio device.

Running Listen

The Listen command has the following syntax:

     Listen [<dmt-args>] [-gain <gain>] [-high <fHi>] [-low <fLow>] <channel>
     

Where:

<dmt-args> The standard DMT DatEnv arguments (e.g. -infile)
-gain <gain> specify an absolute gain. If the gain isn't specified Listen will guess at a gain that will make the signal audible.
-high <fHi> specify a maximum frequency. A filter is added with two real poles at <fHi> and two zeros at fNyquist.
-low <fLow> specify a minimum frequency. A filter is added with two real poles at <fLow> and two zeros at 0 Hz.
<channel> is the name of the channel to be listened to.

When Listen is launched, a control panel is displayed on the device specified by the DISPLAY environment variable. By default all audio ports are disabled. You must select the appropriate port.

Author:
John Zweizig.
Version:
1.2; Last Modified July 25, 2002

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