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118 lines
4.1 KiB
Markdown
118 lines
4.1 KiB
Markdown
<h1>File input plugin</h1>
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<h2>Introduction</h2>
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This plugin reads a file of I/Q samples that have been previously saved with the file record button of other sampling source devices. The plugin supports SDRangel's own .sdriq file format as well as signed 16-bit PCM, 2 channel .wav files (including support for optional auxi headers, containing centre frequency).
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An .sdriq file starts with a 32 byte header of all unsigned integer of various sizes containing meta data:
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<table>
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<tr>
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<th>Displ.</th>
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<th>Bytes</th>
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<th>Description</th>
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</tr>
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<tr>
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<td>0</td>
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<td>4</td>
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<td>Sample rate in S/s</td>
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</tr>
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<tr>
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<td>4</td>
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<td>8</td>
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<td>Center frequency in Hz</td>
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</tr>
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<tr>
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<td>12</td>
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<td>8</td>
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<td>Unix epoch (timestamp) of start</td>
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</tr>
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<tr>
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<td>20</td>
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<td>4</td>
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<td>Sample size (16 or 24 bits)</td>
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</tr>
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<tr>
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<td>24</td>
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<td>4</td>
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<td>Filler with zeroes</td>
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</tr>
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<tr>
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<td>28</td>
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<td>4</td>
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<td>CRC32 of the previous 28 bytes</td>
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</tr>
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</table>
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The header takes an integer number of 16 (4 bytes) or 24 (8 bytes) bits samples. To calculate CRC it is assumed that bytes are in little endian order.
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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: ready to be started
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- Green square icon: currently running and can be stopped
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- Magenta (or pink) square icon: an error occurred. The file may not be found or this can be a header CRC error or the file is too small (less than the header length). You may stop and choose another file.
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<h3>2: Stream sample rate</h3>
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Baseband I/Q sample rate in kS/s. This is the sample rate present in the header.
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<h3>3: Frequency</h3>
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This is the center frequency of reception in kHz when the record was taken and written in the header.
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<h3>4: Open file</h3>
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Opens a file dialog to select the input file. It expects an extension of `.sdriq` or `.wav`. This button is disabled when the stream is running. You need to pause (button 11) to make it active and thus be able to select another file.
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<h3>5: File path</h3>
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Absolute path of the file being read
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<h3>6: File recorded sample rate</h3>
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Sample rate of the record in kS/s as written in the header. The reading process is based on this sample rate.
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<h3>7: Sample size</h3>
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This is the sample size in bits as written in the header. The reading process is based on this sample size.
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<h3>8: CRC indicator</h3>
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Indicates if the header block CRC check has succeeded (green) or failed (red) or undetermined yet (grey). If the header is corrupted you may try to reconstruct a valid header using the `rescuesdriq` utility in the folder with the same name. See the [readme](../../../rescuesdriq/readme.md) for details.
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<h3>9: Current timestamp</h3>
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This is the timestamp of the current pointer in the file based on the start time, number of samples read and sample rate.
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<h3>10: Loop</h3>
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Use this button to read in a loop or read only once
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<h3>11: Play/pause</h3>
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This is the play/pause button
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<h3>12: Playback acceleration</h3>
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Use this combo to select play back acceleration to values of 1 (no acceleration), 2, 5, 10, 20, 50, 100, 200, 500, 1k (1000) times. This is useful on long recordings used in conjunction with the spectrum "Max" averaging mode in order to see the waterfall over a long period. Thus the waterfall will be filled much faster.
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☞ Note that this control is enabled only in paused mode.
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⚠ The result when using channel plugins with acceleration is unpredictable. Use this tool to locate your signal of interest then play at normal speed to get proper demodulation or decoding.
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<h3>13: Relative timestamp and record length</h3>
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Left is the relative timestamp of the current pointer from the start of the record. Right is the total record time.
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<h3>14: Current pointer gauge</h3>
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This represents the position of the current pointer position in the complete recording. It can be used it paused mode to position the current pointer by moving the slider.
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