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README.md 4.4 KiB

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  1. ![Aptdec Logo](textlogo.png)
  2. Copyright (c) 2004-2009 Thierry Leconte (F4DWV), Xerbo (xerbo@protonmail.com) 2019-2022
  3. [![Build](https://github.com/Xerbo/aptdec/actions/workflows/build.yml/badge.svg?branch=master)](https://github.com/Xerbo/aptdec/actions/workflows/build.yml)
  4. ## Introduction
  5. Aptdec is a FOSS program that decodes images transmitted by NOAA weather satellites. These satellites transmit constantly (among other things) medium resolution (4km/px) images of the earth over a analog mode called APT.
  6. These transmissions can easily be received with a cheap SDR and simple antenna. Then the transmission can be decoded in narrow FM mode.
  7. Aptdec can turn the audio recordings into PNG images and generate images such as:
  8. - Raw image: both channels with full telemetry included
  9. - Individual channel: one of the channels form the image
  10. - Temperature image: a temperature compensated image derived from the IR channel
  11. - Palleted image: a image where the color is derived from a palette (false color, etc)
  12. The input audio format can be anything supported by `libsndfile` (although only tested with WAV and FLAC). Sample rate doesn't matter, although lower samples rates will process faster.
  13. ## Quick start
  14. ```sh
  15. sudo apt install cmake git gcc libsndfile-dev libpng-dev
  16. git clone --recursive https://github.com/Xerbo/aptdec.git && cd aptdec
  17. cmake -B build
  18. cmake --build build
  19. # Resulting binary is build/aptdec
  20. ```
  21. ## Examples
  22. To create an image from `gqrx_20200527_115730_137914960.wav` (output filename will be `gqrx_20200527_115730_137914960-r.png`)
  23. ```sh
  24. ./aptdec gqrx_20200527_115730_137914960.wav
  25. ```
  26. To manually set the output filename
  27. ```sh
  28. ./aptdec -o image.png gqrx_20200527_115730_137914960.wav
  29. ```
  30. Decode all WAV files in the current directory and put them in `images`
  31. ```sh
  32. mkdir images && ./aptdec -d images *.wav
  33. ```
  34. Apply a denoise filter (see [Post-Processing Effects](#post-processing-effects) for a full list of post-processing effects)
  35. ```sh
  36. ./aptdec -e d gqrx_20200527_115730_137914960.wav
  37. ```
  38. Create a temperature compensated image for NOAA 18
  39. ```sh
  40. ./aptdec -i t -s 18 gqrx_20200527_115730_137914960.wav
  41. ```
  42. Apply a falsecolor palette
  43. ```sh
  44. ./aptdec -i p -p palettes/WXtoImg-N18-HVC.png gqrx_20200527_115730_137914960.wav
  45. ```
  46. ## Usage
  47. ### Arguments
  48. ```
  49. -i [r|a|b|t|m|p] Output type (stackable)
  50. -e [t|h|l|d|p|f] Effects (stackable)
  51. -o <path> Output filename
  52. -d <path> Destination directory
  53. -s (15-19) Satellite number
  54. -p <path> Path to palette
  55. -r Realtime decode
  56. -g Gamma adjustment (1.0 = off)
  57. ```
  58. ### Image output types
  59. - `r`: Raw Image
  60. - `a`: Channel A
  61. - `b`: Channel B
  62. - `t`: Temperature
  63. - `p`: Palleted
  64. ### Post-Processing Effects
  65. - `t`: Crop telemetry (only effects raw image)
  66. - `h`: Histogram equalise
  67. - `l`: Linear equalise
  68. - `d`: Denoise
  69. - `p`: Precipitation overlay
  70. - `f`: Flip image (for northbound passes)
  71. - `c`: Crop noise from ends of image
  72. ## Realtime decoding
  73. Aptdec even supports decoding in realtime. The following decodes the audio coming from the audio device `pulseaudio alsa_output.pci-0000_00_1b.0.analog-stereo`
  74. ```
  75. mkfifo /tmp/aptaudio
  76. aptdec -r /tmp/aptaudio
  77. sox -t pulseaudio alsa_output.pci-0000_00_1b.0.analog-stereo.monitor -c 1 -t wav /tmp/aptaudio
  78. ```
  79. To stop the decode and calibrate the image simply kill the `sox` process.
  80. ## Palette formatting
  81. Palettes are just simple PNG images, 256x256px in size with 24bit RGB color. The X axis represents the value of Channel A and the Y axis the value of Channel B.
  82. ## Building for Windows
  83. You can cross build for Windows from Linux with the `build_windows.sh` script, you will need the following:
  84. ```
  85. sudo apt install wget cmake make mingw-w64 git unzip
  86. ```
  87. To build natively on Windows using MSVC, you will also need: git, ninja and cmake. Then run:
  88. ```
  89. .\build_windows.bat
  90. ```
  91. If you just wish to build libaptdec on Windows, libpng and libsndfile aren't needed.
  92. ## Further Reading
  93. [User's Guide for Building and Operating
  94. Environmental Satellite Receiving Stations](https://noaasis.noaa.gov/NOAASIS/pubs/Users_Guide-Building_Receive_Stations_March_2009.pdf)
  95. [NOAA KLM coefficients](https://web.archive.org/web/20141220021557/https://www.ncdc.noaa.gov/oa/pod-guide/ncdc/docs/klm/tables.htm)
  96. [NOAA Satellite specifications and more information](https://www1.ncdc.noaa.gov/pub/data/satellite/publications/podguides/N-15%20thru%20N-19/pdf/)
  97. ## License
  98. See `LICENSE`