8/4/2019 Understanding Multimedia Elements (Part 1)

1/19

The decision of which elements to useis often a trade-off between cost, timeor effort

Decrease file size Intellectual property rights Emerging Web technologies

8/4/2019 Understanding Multimedia Elements (Part 1)

2/19

Sound is made when an object vibratesthrough a medium such as air.

When sound reaches your ear, the vibrationsin the molecules move the eardrum backand forth, and those vibrations are cinvertedinto signals that your brain understands as

sound.

8/4/2019 Understanding Multimedia Elements (Part 1)

3/19

8/4/2019 Understanding Multimedia Elements (Part 1)

4/19

When we speak, vibrations, called soundwaves, are created

These sound waves have a recurring pattern

called analog wave patternThe wave pattern has two attributes of

sound on a computer: volume & frequency

8/4/2019 Understanding Multimedia Elements (Part 1)

5/19

Analog sound in the recording world worksby capturing sounds through a device (likemicrophone and transmitting the sound byelectrical means to another device like anamplifier.

Digital storing sound in digital forminvolves converting the signals from analog

means to information the computer canunderstand.

8/4/2019 Understanding Multimedia Elements (Part 1)

6/19

The height of each peak in the sound waverelates to its volume - the higher the peak,the louder the sound

The distance between the peaks is thefrequency (pitch) - the greater the distance,the lower the sound

The amplitude is graphed as the height of

the wave, and frequency is seen as thecurviness of the lines.

8/4/2019 Understanding Multimedia Elements (Part 1)

7/19

Frequency is measured in hertz (Hz) A pattern that recurs every second is equal

to one hertz The pattern that recurs every second is equal to

one hertz

If the pattern recurs 1000 times/sec, it would beequal to 1000 Hz or 1 kHz (kilohertz)

8/4/2019 Understanding Multimedia Elements (Part 1)

8/19

For sound to be included in a multimediaapplication, the sound waves must beconverted from analog (sound waves) todigital (bits) form

This conversion is done through a processcalled sampling

8/4/2019 Understanding Multimedia Elements (Part 1)

9/19

Two factors that affect the quality of thedigitized sound: The number of times the sample is taken (sample

rate)

The amount of information stored about thesample (sample size)

8/4/2019 Understanding Multimedia Elements (Part 1)

10/19

The three most common sample rates: 11.025 kHz

22.05 kHz

44.1 kHz

The higher the sample rate, the moresamples that are taken and thus the betterthe quality of the digitized sound

8/4/2019 Understanding Multimedia Elements (Part 1)

11/19

Two most common sample sizes: 8-bit sample allows for 256 values that are used

to describe the sound

16-bit sample allows for 65,536 values

The higher the sample size, the better thequality of the digitized sound and the largerthe file size

8/4/2019 Understanding Multimedia Elements (Part 1)

12/19

A sound card and software program are usedto digitize sound

A sound from an external source is sent tothe card

The card samples the sound based on thesample rate and bit value, and thenproduces the digital approximation of theanalog signal

8/4/2019 Understanding Multimedia Elements (Part 1)

13/19

Once a sound has been digitized, it caneasily be manipulated using a sound-editingprogram

Sound files can be saved in several fileformats

8/4/2019 Understanding Multimedia Elements (Part 1)

14/19

Popular audio file formats: WAV - developed by Microsoft and IBM; used for

audio on the Web; plays on both Windows & Maccomputers

AIFF (Audio Interchange File Format) and AIFC(AIFF Compressed) - developed by Apple;standard for Mac computers

8/4/2019 Understanding Multimedia Elements (Part 1)

15/19

RealAudio (.ra) - a compression format developedby Real Networks that allows streaming of thesound file over the Web

MP3 (MPEG Layer 3) - a format that compresses

large audio files (entire songs) for playback on theWeb at near stereo quality

8/4/2019 Understanding Multimedia Elements (Part 1)

16/19

MIDI (Musical Instrument Digital Interface) - astandard format that enables computers andelectronic musical instruments to communicatesound information

8/4/2019 Understanding Multimedia Elements (Part 1)

17/19

A primary consideration when using soundon the Web is file size

Through a process called file compression,the size of a file can be reduced significantly

File compression is automatically performedwhen audio files are saved using certain fileformats.

Compression can be lossless or lossy. With

lossy compression, some of the soundquality is lost to achieve smaller file sizes.

When using lossless compression, no qualityin the audio is lost when reproducing the

sound.

8/4/2019 Understanding Multimedia Elements (Part 1)

18/19

Sound files delivered via the Web are storedon a server

A server is a computer with software thatresponds to other computers and makesdata and programs available to them

8/4/2019 Understanding Multimedia Elements (Part 1)

19/19

Streaming media is a technology thatallows audio and video to be played in realtime

A media player must be installed on acomputer to stream sound files through theWeb