Chapter5 Midi

7/31/2019 Chapter5 Midi

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2/16/2011

COM 205

Multimedia Programming


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2/16/2011

Chapter 5

Sound


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Overview

Introduction to sound.

Multimedia system sound.

Digital audio.

MIDI audio.

Audio file formats.


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Overview

MIDI versus digital audio.

Adding sound to multimedia project.

Professional sound.

Production tips.


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Power of Sound

Vibrations in the air create waves ofpressure that are perceived as sound.

Sound waves vary in sound pressure level

(amplitude) and in frequency. Acoustics is the branch of physics that

studies sound.

Sound pressure levels (loudness or

volume) are measured in decibels (dB). Humans hear sound over a very broad

range


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Sound

Sound is energy, caused bymolecules vibrating

Too much volume can permanently

damage your ears and hearing The perception of loudness depend

on the frequency


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Using Sound in Multimedia

You need to know

How to make sounds

How to record and edit sounds on thecomputer

How to incorporate sounds into yourmultimedia project


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Multimedia System Sounds

System sounds are assigned to varioussystem events such as startup andwarnings, among others.

Macintosh provides several system soundoptions such as glass, indigo, laugh.

In Windows, available system soundsinclude start.wav, chimes.wav, and

chord.wav.

Multimedia sound is either digitallyrecorded audio or MIDI (Musical

Instrumental Digital Interface) music.


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Most computers have sounds readyto use


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Mac and Windows have built insound recorders


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MIDI Audio

MIDI is a series of musicalinstructions

Click to play


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MIDI vs. Digital Audio

MIDI ( Musical Instrument DigitalInterface) is a communicationsstandard developed in the 1980s forelectronic instruments andcomputers.

It allows instruments from differentmanufacturers to communicate.


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MIDI data is NOT digitized sound- it ismusic stored in numeric format

Digital audio is a recording, which depend

on your sound system MIDI is a score and depends on both the

quality of the instruments and the soundsystem

Quality depends on end users devicerather than on the MIDI device and isdevice dependent.


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Making MIDI Audio

Creating a MIDI score requires: Knowledge of music and some talent

Ability to play a musical instrument

Sequencer software

Sound synthesizer Built into PC board

Add-on for MAC

MIDI can synthesize over 100 instruments


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Making MIDI Audio

You will need:

Sequencer Software (Smart Score)

A Sound synthesizer ( built into PCsound board, an add on for MAC)

MIDI keyboard or device

Ability to play the piano and musictheory background

or a hired expert


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MIDI

A MIDI file is a list of commands thatare recordings of musical actions,that when sent to a MIDI playerresults in sound

MIDI data is device dependent

MIDI represents musical instrumentsand is not easily used to playbackspoken dialog


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MIDI Audio

MIDI is a shorthand representation ofmusic stored in numeric form.

Since they are small, MIDI files embedded

in web pages load and play promptly. Length of a MIDI file can be changed

without affecting the frequency of themusic or degrading audio quality.

Working with MIDI requires knowledge ofmusic theory.


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Digital Audio

Digital audio is a representationof the original sound

Sampling rate is measured inkilohertz (kHz)

Click to play


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Digital Audio

Digital audio represents a soundstored in thousands of numbers orsamples.

Digital data represents theloudness at discrete slices of time.

It is NOT device dependent and

should sound the same each time itis played

It is used for music CDs


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Digital Audio

The three sampling frequencies most oftenused in multimedia are CD-quality 44.1kHz, 22.05 kHz and 11.025 kHz.

The number of bits used to describe theamplitude of sound wave when sampled,determines the sample size.

Digital audio is device independent.

The value of each sample is rounded off tothe nearest integer (quantization).


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Preparing Digital Audio

Balance file size versusquality

Set recording levels

Edit the recording


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Preparing Digital Audio

Balance file size versus quality

To calculate file size in bytes:

Mono: sampling rate duration of recording

in seconds (bit resolution 8) 1

Stereo: sampling rate duration of recording

in seconds (bit resolution 8) 2


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Digital Audio Editing

Once a recording had been completed, it

almost always needs to be edited.

Basic sound editing operations include:

trimming, splicing and assembly, volume

adjustments and working on multiple

tracks.


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Digital Audio Editing

Additional available sound editing

operations include format conversion,

resampling or downsampling, fade-ins and

fade-outs, equalization, time stretching,

digital signal processing, and reversing

sounds.


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MIDI data and digital audio are likevector and bitmapped graphics:

Digital audio like bitmapped imagesamples original to create a copy

MIDI like vector graphic- storesnumeric data to recreate sound


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MIDI data is device dependent; digitalaudio is not

MIDI sounds (like vector graphics)are different on different devices;

Digital sounds are identical even ondifferent computers or devices.


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MIDI Advantages

MIDI file are much more compact andtake up less memory and systemresources

MIDI files embedded in web pagesload and play much faster than digital

You can change the length of a MIDIfile by varying its tempo

With high quality MIDI devices, MIDIfiles may actually sound better thandigital


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MIDI Disadvantages

MIDI represents musical instrumentsnot sounds and will be accurate onlyif your playback device is identicalto the production device

MIDI sound is inconsistent

MIDI cannot be easily used toreproduce speech


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Digital Audio Advantages

Digital audio sound is consistent anddevice independent

A wide selection of software supportis available for both MAC and PC

A knowledge of music theory is notrequired for creating digital audio,but usually is needed for MIDIproduction


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Choose MIDI data

If you dont have enough RAM

memory, or bandwidth for digitalaudio

If you have a high quality soundsource

If you have complete control over theplayback hardware

If you dont need spoken dialog


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Choose Digital Audio

If you dont have control over the

playback hardware

If you have the computing resourcesand bandwidth to handle the largerdigital files

If you need spoken dialog


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Digital Audio

You can digitize sound from amicrophone, synthesizer, taperecording TV broadcast, or CDs.

Digitized sound is sampled every nthof a second. The more often you takethe sample, the better the sound.

Sample sizes are either 8 or 16 bitsand common frequencies are11.025,22.05, and 44.1 kHz (See pp. 209- 211)


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Digital Audio

To prepare digital audio from analogmedia, record it from a device, like atape recorder, into your computerusing digitizing software.

Balance the sound quality with youravailable RAM

Set proper recording levels for agood clear recording


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File Size vs. Quality

Audio resolution determines theaccuracy with which a sound isdigitized. (More bits in the sample

size produces better quality andlarger files)

Stereo recordings are more realistic

and require twice as much storagespace and playback time.

Mono files tend to sound flat


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Editing Digital Recordings

Apples QuickTime Player Proprovides for primitive playback andediting

Sonic Foundrys Sound Forge is amore serious sound editor

These can be used to trim, splice,

volume adjustment and formatconversion as well as special effects


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Audio File Formats

A sound files format is a recognizedmethodology for organizing data bits ofdigitized sound into a data file.

On the Macintosh, digitized sounds maybe stored as data files, resources, orapplications such as AIFF or AIFC.

In Windows, digitized sounds are usuallystored as WAV files.

Both can use MIDI files (.mid)


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Audio File Formats

CD-ROM/XA (Extended Architecture)format enabled several recordingsessions to be placed on a single

CD-R (recordable) disc.

Linear Pulse Code Modulation isused for Red Book Audio data files

on consumer-grade music CDs.


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Sound for the World Wide Web

To play MIDI sound on the web wait for the entire file to download and

play it with a helper application

stream the file, storing it in the buffer andplaying it while it downloads

Streaming is dependent on theconnection speed

FLASH allows sound to be integratedin a multimedia presentation,controlled by buttons and saved as

.mp3

Adding Sound to a


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Adding Sound to a

Multimedia Project

Decide what sounds you will need andinclude them in the story board or cuesheet.

Decide whether to use MIDI or digitalaudio

Acquire source material (record/buy)

Edit the sounds

Test the sounds to be sure they aretimed properly


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Adding sound to Multimedia

CD- quality audio

Standard is ISO 10149, a.k.a. the Red Book Standard

Sample size is 16-bit

Sample rate is 44.1 kHz

11 seconds of audio uses 1.94 MB of space


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Professional Sound

The Red Book Standard- ISO 10149

( 16 bits at 44.1 kHz) allows accuratereproduction of all sounds humans can

hear

Software such as Toast and CD-Creatorcan translate digital files from CDs

directly into a digital sound editing fileor decompress.mp3 files into CD-Audio


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Professional Sound

Compression techniques reduce space butreliability suffers.

Space can be conserved by downsampling

or reducing the number of sample slicestaken per second.

File size of digital recording (in bytes) =sampling rate X duration of recording (insecs) X (bit resolution/8) X number oftracks.


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Advanced Sound Management

Scripting Languages such as OpenScript (Toolbook), LINGO(Director),or Action Script ( FLASH) provide

better control over audio playback

Requires some programmingknowledge


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Production Tips

Vaughns Law of Minimums - there isan acceptable level of adequacy thatwill satisfy the audience;

If your handheld microphone is goodenough to satisfy you and youraudience, conserve your money and

energy.


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Production Tips

Recording on inexpensive mediarather than directly to diskprevents the hard disk from being

overloaded with unnecessary data.

The equipment and standardsused for the project must be in

accordance with the requirements.

Sound and image synchronizationmust be tested at regular intervals


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Production Tips

Audio recording - use CDs, or VCRtapes, or DAT ( digital audio tape)tapes

Create a good database to organizeyour sounds, noting the counter andcontent

Testing and Evaluating- (delaying afast machine if needed to sync withanimation)


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Production Tips

Copyright Issues

Securing permission for the use ofsounds and music is the same as forimages

Can buy royalty-free digitized soundclips

DO NOT use someones original

work without permission!


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Summary

Vibrations in air create waves of pressurethat are perceived as sound.

Multimedia system sound is digitally

recorded audio or MIDI (MusicalInstrumental Digital Interface) music.

Digital audio data is the actualrepresentation of a sound, stored in theform of samples.


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Summary

MIDI is a shorthand representation ofmusic stored in numeric form.

Digital audio provides consistent playbackquality.

MIDI files are much smaller than digitizedaudio.

MIDI is device dependent digital audio isnot

MIDI files sound better than digital audiofiles when played on high-quality MIDIdevice.

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