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Basic attempt at injecting and reading back user data unregistered (UDU) supplemental enhancement information (SEI) with ffmpeg / libav.

Some references:

• https://ffmpeg.org/doxygen/trunk/group__lavu__frame.html#ggae01fa7e427274293aacdf2adc17076bca4f2dcaee18e5ffed8ff4ab1cc3b326aa
• https://gist.github.com/figgis/d3cff69be815491eff1ac9338aa78add
• https://stackoverflow.com/q/74431792

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#!/usr/bin/env python3

import numpy as np
import matplotlib.pyplot as plt

def wavelength_to_rgb(wavelengths, gamma=0.8):
    '''This converts a given wavelength of light to an
    approximate RGB color value. The wavelength must be given
    in nanometers in the range from 380 nm through 750 nm
    (789 THz through 400 THz).

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A simple PyTorch implementation of plane fitting with RANSAC. Some ideas are taken from: https://github.com/leomariga/pyRANSAC-3D.

In each (batched-)RANSAC iteration, a batch of triplets is sampled and assessed in parallel. A cross-product is used to get plane equations from triplets. The refinement, post identification of inliers, is done with an eigen decomposition of P.T @ P where P is the matrix of points in homogeneous coordinates. Classicially, an SVD decomposition of P is used but this can be slow and memory intensive with large number of points. We thus opted for the eigen decomposition approach despite it being less numerically stable.

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Hack file to get a nicer Gist name

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import numpy as np
import matplotlib.pyplot as plt
import imageio
url = 'https://archive.org/download/10thframekixxc64800dpi48bit/10th%20Frame%20%28Kixx%29_C64_Cassette_800dpi_48bit.tif'
im0 = imageio.imread(url)
print('im0:',np.min(im0),np.max(im0),im0.shape,im0.dtype)

im0gray = 0.299*np.float32(im0[:,:,0]) + 0.587*np.float32(im0[:,:,1]) + 0.114*np.float32(im0[:,:,2])
im0gray = im0gray / np.max(im0gray)
im1 = np.uint16(np.round( im0gray*((1<<10)-1) ))

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Spectral information

https://omlc.org/spectra/hemoglobin/summary.html https://omlc.org/spectra/icg/

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#EXTM3U
#EXTINF:0,Radio France - FIP (AAC+Metadata)
http://radio-metadata.fr:8000/fip.m3u
#EXTINF:0,Radio France - FIP Reggae (AAC+Metadata)
http://radio-metadata.fr:8000/fipreggae.m3u
#EXTINF:0,Radio France - FIP Cultes (AAC+Metadata)
http://radio-metadata.fr:8000/fipcultes.m3u
#EXTINF:0,Radio France - FIP World (AAC+Metadata)
http://radio-metadata.fr:8000/fipmonde.m3u
#EXTINF:0,Radio France - FIP Nouveautés (AAC+Metadata)

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Hack file to get a nicer Gist name

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#!/bin/sh

# Sanity checks
if ! [ -x "$(command -v gs)" ]; then
    echo "gs is not installed -> exit"
    exit 1
fi

# Define some handy options to use with ghostscript
export PDF2PDFFLAGS="-dCompatibilityLevel=1.5 -dPDFSETTINGS=/ebook -dPrinted=false -dColorConversionStrategy=/UseDeviceIndependentColor -dDownsampleColorImages=true -dDownsampleGrayImages=true -dDownsampleMonoImages=true -dMaxSubsetPct=100 -dSubsetFonts=true -dEmbedAllFonts=true -dOptimize=true -dUseFlateCompression=true -dNOPAUSE -dBATCH -sDEVICE=pdfwrite"