Computerphile | Programming with Proofs - Computerphile @Computerphile | Uploaded 3 years ago | Updated 15 hours ago
Continuing our look at the Agda programming language, Professor Thorsten Altenkirch shows us how you can work with proofs, which could be invaluable in some industrial situations.

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This video was filmed and edited by Sean Riley.

Computer Science at the University of Nottingham: bit.ly/nottscomputer

Computerphile is a sister project to Brady Haran's Numberphile. More at http://www.bradyharan.com

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$How NOT to Sample Audio! - Computerphile Could Dave recreate audio from a wav file preview image grabbed from a screen cap? More about David Domminney Fowler: https://youtube.com/c/DavidDomminneyFowler https://www.facebook.com/computerphile https://twitter.com/computer_phile This video was filmed and edited by Sean Riley. Computer Science at the University of Nottingham: https://bit.ly/nottscomputer Computerphile is a sister project to Brady Harans Numberphile. More at http://www.bradyharan.com Original Image: https://photos.app.goo.gl/c4pPY8xpCF6cNmTF8 Daves Code: (angle brackets werent allowed in YT description) using System; using System.Collections.Generic; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; namespace Extract_Audio { internal class Program { private static void Main(string[] args) { string file = computerphile.png; Bitmap b = new Bitmap(@g:Computerphile + file); var values = new System.Collections.Generic.ListANGLEBRACKETOPENintANGLEBRACKETCLOSE(); for (int x = 0; x ANGLEBRACKETOPEN b.Width; x++) { int max = 0; int min = b.Height; for (int y = 0; y ANGLEBRACKETOPEN b.Height; y++) { if (b.GetPixel(x, y).GetBrightness() ANGLEBRACKETCLOSE 0.5) { min = Math.Min(y, min); max = Math.Max(max, y); } } values.Add(min); values.Add(max); } int filter = 4; for (int x = 0; x ANGLEBRACKETOPEN values.Count - filter; x++) values[x] = (int)values.GetRange(x, filter).Average(); var f = new System.IO.StreamWriter($@g:Computerphile{file}.txt); foreach (var v in values) f.WriteLine(v); f.Close(); var wf = System.IO.File.OpenWrite($@g:Computerphile{file}.wav); var RIFF_HEADER = new byte[] { 0x52, 0x49, 0x46, 0x46 }; var FORMAT_WAVE = new byte[] { 0x57, 0x41, 0x56, 0x45 }; var FORMAT_TAG = new byte[] { 0x66, 0x6D, 0x74, 0x20 }; var AUDIO_FORMAT = new byte[] { 0x1, 0x0 }; var SUBCHUNK_ID = new byte[] { 0x64, 0x61, 0x74, 0x61 }; int BYTES_PER_SAMPLE = 1; int samplerate = 48000; int channelcount = 1; int lastv2 = 0; int stretch = 9; int datalength = values.Count * stretch * BYTES_PER_SAMPLE; int byteRate = samplerate * channelcount * BYTES_PER_SAMPLE; int blockAlign = channelcount * BYTES_PER_SAMPLE; wf.Write(RIFF_HEADER, 0, RIFF_HEADER.Length); wf.Write(BitConverter.GetBytes(datalength + 40), 0, 4); wf.Write(FORMAT_WAVE, 0, FORMAT_WAVE.Length); wf.Write(FORMAT_TAG, 0, FORMAT_TAG.Length); wf.Write(BitConverter.GetBytes(16), 0, 4); wf.Write(AUDIO_FORMAT, 0, AUDIO_FORMAT.Length); wf.Write(BitConverter.GetBytes(channelcount), 0, 2); wf.Write(BitConverter.GetBytes(samplerate), 0, 4); wf.Write(BitConverter.GetBytes(byteRate), 0, 4); wf.Write(BitConverter.GetBytes(blockAlign), 0, 2); wf.Write(BitConverter.GetBytes(BYTES_PER_SAMPLE * 8), 0, 2); wf.Write(SUBCHUNK_ID, 0, SUBCHUNK_ID.Length); wf.Write(BitConverter.GetBytes(datalength), 0, 4); foreach (var v in values) { double v2 = (v - values.Min()) / (double)(values.Max() - values.Min()) * 255; for (int x = 0; x ANGLEBRACKETOPEN stretch; x++) { double v3 = x / (double)stretch * v2 + (1 - x / (double)stretch) * lastv2; wf.WriteByte(Convert.ToByte(v3)); } lastv2 = (int)v2; } wf.Close(); } } }$

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