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66 lines
2.7 KiB
Markdown
66 lines
2.7 KiB
Markdown
<h1>Audio input plugin</h1>
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<h2>Introduction</h2>
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This input sample source plugin gets its samples from an audio device.
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<h2>Interface</h2>
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The top and bottom bars of the device window are described [here](../../../sdrgui/device/readme.md)
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<h3>1: Start/Stop</h3>
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Device start / stop button.
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- Blue triangle icon: device is ready and can be started
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- Green square icon: device is running and can be stopped
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- 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.
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<h3>2: Auto remove DC component</h3>
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Software DSP auto remove DC correction. This will work in I/Q mode (stereo I/Q) only.
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<h3>3: Auto make I/Q balance</h3>
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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.
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<h3>4: Device</h3>
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The audio device to use.
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<h3>5: Refresh devices</h3>
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Refresh the list of audio devices.
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<h3>6: Audio sample rate</h3>
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Audio sample rate in Hz (Sa/s).
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<h3>7: Decimation</h3>
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A decimation factor to apply to the audio data. The baseband sample rate will be the audio sample, divided by this decimation factor.
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<h3>8: Decimated bandpass center frequency position relative to the device center frequency</h3>
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This will work in I/Q mode (stereo I/Q) only.
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- **Cen**: the decimation operation takes place around the device center frequency Fs
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- **Inf**: the decimation operation takes place around Fs - Fc.
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- **Sup**: the decimation operation takes place around Fs + Fc.
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<h3>9: Volume</h3>
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A control to set the input volume. This is not supported by all input audio devices.
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<h3>10: Channel Map</h3>
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This controls how the left and right audio channels map on to the IQ channels.
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* 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.
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* Mono R - Same as above but takes the right audio channel for the real signal.
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* 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.
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* 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.
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