multimedia lecture 3

Multimedia & Web Multimedia & Web DevelopmentDevelopment

SOUNDSOUND

Associate Professor Ravindra KoggalageAssociate Professor Ravindra Koggalage

Pragathi WeerakoonPragathi Weerakoon

[email protected]@yahoo.com

SoundSoundSound is perhaps the most Sound is perhaps the most sensuous element of multimedia. sensuous element of multimedia.

The Power of SoundThe Power of Sound•When something vibrates in the air by moving back and forth, it creates waves of pressure. These waves spread, and when they reach your eardrums, you experience the vibrations as sound.•Acoustics is the branch of physics that studies sound•Sound pressure levels (loudness or volume) are measured in decibels (dB)

Multimedia System SoundsMultimedia System SoundsSoundSound

Digital AudioDigital AudioSoundSound

When represent a sound wave using numbers, created digital audio.


Preparing Digital Audio FilesPreparing Digital Audio Files

File size Versus Quality

Size formula of digital recordingrecording

sampling rate **

duration of recording in

seconds**

(bitresolution / 8) ** 1MonoMono

sampling rate **

duration of recording in

seconds**

(bit resolution / 8) ** 2StereoStereo

File File SizeSize

QualityQuality



Setting Proper Recording Level

Consumer –grade audio compact discs are recorded in stereo at s sampling rate of 44.1 kHz and a 16 bit resolution. Other sampling rates include 22.05 and 11 kHz, at either 16 or 8 bits.When recording (digitizing) audio, it is important to keep the recording level near the maximum without going over it.Important steps in digital sound editing include removing blank space from the start and end of a recording and normalizing the sound to bring all clips to approximately the same level.



Setting Proper Recording Level

Multiple TracksTrimmingSplicing and AssemblyVolume AdjustmentsFormat ConversionResampling or DownsamplingFade-ins and Fade-outsEqualizationTime StretchingDigital Signal Processing (DSP)Reversing sounds

Editing Digital Recording

Making MIDI AudioMaking MIDI AudioSoundSound

MIDI- Musical Instrument Digital MIDI- Musical Instrument Digital InterfaceInterface

a)MIDI data is not digitalized sound; it is a short hand representation of music stored in numeric form.

b)b)MIDI files tend to be significantly MIDI files tend to be significantly smaller than equivalent smaller than equivalent digitalized waveform files.digitalized waveform files.

c)MIDI data is device dependant; it is playback depends of the capabilities of the end user’s system.

d)d)Because they are small, MIDI files Because they are small, MIDI files embedded in web pages load and embedded in web pages load and play more quickly than their play more quickly than their digital equivalent.digital equivalent.

Making MIDI AudioMaking MIDI AudioSoundSound

MIDI- Musical Instrument Digital MIDI- Musical Instrument Digital InterfaceInterface

e)You can change the length of a MIDI file (by varying its tempo) without changing the pitch of the music or degrading the audio quality. MIDI data is completely editable.

f)f) MIDI can not easily be used to MIDI can not easily be used to play back spoken dialog.play back spoken dialog.

g)Working with MIDI required familiarity with musical stores, keyboards, and notation as well as audio production.

Audio File FormatsAudio File FormatsSoundSound

a)Digital audio data is the actual representation of a sound, stored in the form of thousands of individual samples that represent the aplitude (or loudness) of a sound at a discrete point in time.

b)How often the samples are taken in the sampling rate.

c)Three sampling frequencies – a)CD quality 44.1 kHzb)22.05 kHzc)11.025 kHz

d)Digital audio is not device dependant, and sounds the same every time it is determined by the number of bits used to describe the amplitude of the sound wave when the sample is taken

Audio File FormatsAudio File FormatsSoundSound

e)Sample sizes are either 8 bites or 16 bits.

f) The value of each sample is rounded off to the nearest integer (quantization)

g)The preparation and programming required for creating digital audio do not demand knowledge of music theory.

MIDI Vs Digital AudioMIDI Vs Digital Audioi. MIDI is analogous to structured

or vector graphics, while digitized audio is analogous to bitmapped images.

ii.MIDI is device dependant, while digitized audio is device independent.

iii.Use MIDI only when you have control over the playback hardware and know users will be use high quality MIDI device for playback

SoundSoundMIDI Vs Digital AudioMIDI Vs Digital Audio

iv.MIDI files are much smaller than digitized audio, so they may be used for delivery of music under the right circumstances.

v. Use digitized audio for spoken dialogue.Sound for the world wide webSound for the world wide web

.au (µLaw)[8kHz-8/16bits] More types(aLaw)

BufferStreamingBand widthAdobe’s Flash

SoundSoundAdding Sound to your Multimedia Adding Sound to your Multimedia ProjectProject1. Determine the file formats that

are compatible with your multimedia authoring software and the delivery medium(s) you will be using (for file storage and bandwidth capacity)

2. Determine the sound playback capebilities (codes and plug-ins) that the end user’s system offers.

3. Decided what kind of sound needed (such as background music, special sound effects, and spoken dialogue). Decide where these audio events will occur in the flow of your project. Fit the sound cues into your storyboard, or make up a cue sheet.

SoundSoundAdding Sound to your Multimedia Adding Sound to your Multimedia ProjectProject4. Decide where and when you want

to use either digital audio or MIDI data.

5. Acquire source material by creating it from scratch or purchasing it.

6. Edit the sounds to fit your project.

7. Test the sound to be sure they are timed properly with the project’s images. This may involve repeating steps 1 through 4 until everything is in sync.

SoundSoundMusic CDsMusic CDs

1. International standard ISO 10149 Red BookRed Book

2.2. 16 bits at 44.1 kHz and at 48 kHz16 bits at 44.1 kHz and at 48 kHz3.3. Burning software (Toast, Roxio) Burning software (Toast, Roxio)

translate to MP3 or WAV or CD translate to MP3 or WAV or CD Audio formatAudio format

Space ConsiderationsSpace ConsiderationsEstimate your storage needs

(Sampling rate * bits per sample)/8=bytes per second

sample rate * sample size/8*# seconds*2=file size in KB

Example:60 seconds of stereo in Red

Book Audio:44.1*1608*60*2 = 10,584KB =

10.59MB

SoundSoundProduction TipsProduction Tips

Audio recordingKeeping track of your soundTesting and evaluationCopyright Issues

There is an acceptable minimum There is an acceptable minimum level of adequacy that will satisfy level of adequacy that will satisfy the audience, even when that the audience, even when that level may not be the best that level may not be the best that technology, money or time and technology, money or time and effort can buy.effort can buy.

Vaughan’s Law of Multimedia Vaughan’s Law of Multimedia MinimumsMinimums

multimedia lecture 3

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