Audio input plugin

Introduction

This input sample source plugin gets its samples from an audio device.

Interface

The top and bottom bars of the device window are described [here](../../../sdrgui/device/readme.md) ![Audio input plugin GUI](../../../doc/img/AudioInput_plugin.png)

1: Start/Stop

Device start / stop button. - Blue triangle icon: device is ready and can be started - Green square icon: device is running and can be stopped - Magenta (or pink) square icon: an error occurred. In the case the device was accidentally disconnected you may click on the icon, plug back in and start again.

2: Auto remove DC component

Software DSP auto remove DC correction. This will work in I/Q mode (stereo I/Q) only.

3: Auto make I/Q balance

Software DSP auto I/Q imbalance correction. The DC correction (8) must be enabled for this to be effective. This will work in I/Q mode (stereo I/Q) only.

4: Device

The audio device to use.

5: Refresh devices

Refresh the list of audio devices.

6: Audio sample rate

Audio sample rate in Hz (Sa/s).

7: Decimation

A decimation factor to apply to the audio data. The baseband sample rate will be the audio sample, divided by this decimation factor.

8: Decimated bandpass center frequency position relative to the device center frequency

This will work in I/Q mode (stereo I/Q) only. - **Cen**: the decimation operation takes place around the device center frequency Fs - **Inf**: the decimation operation takes place around Fs - Fc. - **Sup**: the decimation operation takes place around Fs + Fc.

9: Volume

A control to set the input volume. This is not supported by all input audio devices.

10: Channel Map

This controls how the left and right audio channels map on to the IQ channels. * Mono L - Real samples are taken from the left audio channel and are heterodyned by the fourth of the sample rate (fs/4) to obtain complex samples. Therefore the spectrum of the complex baseband is centered at the fourth of the sample rate (fs/4). As per Nyquist rule only a bandwidth of half of the sample rate (fs/2) is available for real signals. Frequencies outside the [0, fs/2] interval are artefacts and can be eliminated by decimating by a factor of 2. * Mono R - Same as above but takes the right audio channel for the real signal. * I=L, Q=R - The left audio channel is driven to the I channel. The right audio channel is driven to the Q channel for a complex (analytic signal)input. * I=R, Q=L - The right audio channel is driven to the I channel. The left audio channel is driven to the Q channel for a complex (analytic signal)input.