CSCI 1101A Sound Ch. 6, 7, 8 [MultimediaGuzdial] Mohammad T . - PDF document

10/28/14 ¡ CSCI 1101A Sound Ch. 6, 7, 8 [Multimedia—Guzdial] Mohammad T . Irfan 10/21/14 – 10/24/14 Announcement u Exam 3 u Tuesday, Oct 28 u Topics u Chapters 4, 5 (5.1, 5.2, 5.3, 5.6), 6 u Duration and types of questions: same as before u How to prepare u Practice codes from the book + slides u Solve exercise problems at the end of the above chapters u Recommended exercise problems u 4.5, 4.7, 4.15 u 5.16, 5.18, 5.25 u 6.7, 6.9, 6.12 1 ¡

10/28/14 ¡ Physics of sound à computation Example: Ponoplayer u http://www.digitaltrends.com/music/neil- youngs-pono-hi-def-mp3-player/#!BBxl3 2 ¡

10/28/14 ¡ Basic sound functions (vs. picture functions) u makeSound(f) u makePicture(f) u getSamples(sndObj) u getPixels(picObject) u getSampleObjectAt(sndObj, idx) u getPixel(picObject, x, y) u getLength(sObject) u getWidth(picObject), getHeight(…) u getSampleValue(sample) u getColor(px) u getSampleValueAt(sndObj, idx) u (no direct function) u setSampleValue(sample, val) u setColor(px, color) u setSampleValueAt(sndObj, idx, u (no direct function) val) Problem: Increase volume u volume => amplitude => sample values u Make the volume 5 times the original volume => u Make each sample value 5 times the original 3 ¡

10/28/14 ¡ Code Problem: Make the first quarter louder, the rest quieter u Different operations on different parts of sound u Can we use indexing to access specific samples? 4 ¡

10/28/14 ¡ Code Review u Each rectangle is a sample and has a sample value between -32767 and +32768 5 ¡

10/28/14 ¡ Review u getSamples(soundObject) u getLength(soundObject) u getSampleValue(sample) vs. getSampleValueAt(soundObject, index) u setSampleValue(sample, val) vs. setSampleValueAt(soundObject, index, val) Problem: Normalize sound u Want max sample value to be (+/-)32767 u Other sample values to be changed accordingly u Algorithm u Step 1: Find max abs(sample value) u Step 2: Multiply each sample value by 32767.0/ max 6 ¡

10/28/14 ¡ Code: Step 1 Code: Step 2 7 ¡

10/28/14 ¡ Useful function: clip u Make a new sound object with only part of a give sound object Code 8 ¡

10/28/14 ¡ Useful function: copy u Copy source sound to target sound beginning at a desired target index u Target sound object must be big enough to hold the source Code 9 ¡

10/28/14 ¡ Problem: Insert another sound into a given sound object (splicing) u Have (preamble10.wav): “We the people of the United States” u Want: “We the united people of the United States” u Algorithm u Clip “united” and save it as a new sound object u Make a big enough target sound object u Copy “We the” to target u Copy “united” to target u Copy “people of the United States” to target preamble10.wav preamble10.wav 10 ¡

10/28/14 ¡ Code Misc. Topics (Ch 8) u Blending sounds (Section 8.2) u Playing MIDI (Section 8.6) u playNote(noteFrequency, duration [, intensity]) 11 ¡