Computerphile | Program Correctness - Computerphile @Computerphile | Uploaded 3 years ago | Updated 14 hours ago
Program Correctness is incredibly important in computing - particularly in hardware design. Professor Graham Hutton takes us through a simple example using arithmetic.

EXTRA BITS: youtu.be/TByzerWLKg8

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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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