kopia lustrzana https://github.com/dnet/pySSTV
72 wiersze
2.7 KiB
Markdown
72 wiersze
2.7 KiB
Markdown
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SSTV generator in pure Python
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=============================
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PySSTV generates SSTV modulated WAV files from any image that PIL can open
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(PNG, JPEG, GIF, and many others). These WAV files then can be played by any
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audio player connected to a shortwave radio for example.
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My main motivation was to understand the internals of SSTV in practice, so
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performance is far from optimal. I tried keeping the code readable, and only
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performed such optimizations that wouldn't have complicated the codebase.
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Command line usage
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------------------
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usage: run.py [-h]
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[--mode {MartinM2,MartinM1,Robot24BW,ScottieS2,ScottieS1,Robot8BW}]
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[--rate RATE] [--bits BITS]
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image.png output.wav
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Converts an image to an SSTV modulated WAV file.
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positional arguments:
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image.png input image file name
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output.wav output WAV file name
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optional arguments:
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-h, --help show this help message and exit
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--mode {MartinM2,MartinM1,Robot24BW,ScottieS2,ScottieS1,Robot8BW}
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image mode (default: Martin M1)
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--rate RATE sampling rate (default: 48000)
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--bits BITS bits per sample (default: 16)
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Python interface
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----------------
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The `SSTV` class in the `sstv` module implements basic SSTV-related
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functionality, and the classes of other modules such as `grayscale` and
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`color` extend this. Most instances implement the following methods:
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- `__init__` takes a PIL image, the samples per second, and the bits per
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sample as a parameter, but doesn't perform any hard calculations
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- `gen_freq_bits` generates tuples that describe a sine wave segment with
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frequency in Hz and duration in ms
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- `gen_values` generates samples between -1 and +1, performing sampling
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according to the samples per second value given during construction
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- `gen_samples` generates discrete samples, performing quantization
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according to the bits per sample value given during construction
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- `write_wav` writes the whole image to a Microsoft WAV file
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The above methods all build upon those above them, for example `write_wav`
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calls `gen_samples`, while latter calls `gen_values`, so typically, only
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the first and the last, maybe the last two should be called directly, the
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others are just listed here for the sake of completeness and to make the
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flow easier to understand.
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License
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-------
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The whole project is available under MIT license.
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Useful links
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------------
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- receive-only "counterpart": https://github.com/windytan/slowrx
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- free SSTV handbook: http://www.sstv-handbook.com/
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Dependencies
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------------
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- Python 2.7 (tested on 2.7.5)
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- Python Imaging Library (Debian/Ubuntu package: `python-imaging`)
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