Audio video

Kolej Kemahiran Tinggi MARA
Rembau, Negeri Sembilan

INFORMATION SHEET

COURSE: Digital Video And Audio
SESSION : July-Dec 2012 SEMESTER : 3

CODE/SUBJECT : SHEET NO : 1
LECTURER : Ahmad Kamsol Bin Mat Yusop WEEK : 1

TOPIC : Introduction to Digital Audio System

1.1. History
1.2. Understand Analog and Digital Audio
SUB-TOPIC : 1.3. File Size
1.4. Digital Audio Format

After completing this chapter, students will be able to:
1. Understand the history of digital audio system
LEARNING 2. Understand the different between analog and digital audio
OUTCOME :
3. Explain type of file size in digital audio system
4. Interpret about digital audio format

Digital Video And Audio – Ahmad Kamsol Bin Mat Yusop Information Sheet 1

UNIT 1: Introduction to Digital Audio System

1. Digital audio is the process of converting media from analog to digital form (digitizing)
is achieved through a process called sampling.
2. The most common method of creating digital audio is Pulse-code modulation (PCM)
ADCs and DACs

Real sound input ADC - Analog to Digital Converter
-Recorder through microphone

Reproduce sound DAC - Digital to Analog Converter

Sampling Process

1. Here is an analog 2. To digitize sound, 3. These samples are
sound wave. Analog samples are taken at trimmed to the nearest
sound is continuous even intervals of times value and encoded in
variation in air binary
pressure.


1.1. History of Audio

History of Audio Format
An audio format is a medium for storing sound and music. Music is recorded and distributed
using a variety of audio formats, some of which store additional information

Timeline of audio format developments.

Year Media formats Recording formats

1877 Mechanical analog; "hill-and-dale" grooves, vertical
stylus motion

Phonograph cylinder

1883 Mechanical digital (automated musical instruments)

Music roll

1895 Mechanical analog; lateral grooves, horizontal stylus
motion

Gramophone record

1898 Analog; magnetization; no "bias"

Wire recording


1925 Electrical cut record Mechanical analog; electrically cut from amplified
microphone signal, lateral grooves, horizontal stylus
motion, discs at 7", 10", 12", most at 78 rpm

1930 Analog; magnetization; "bias" dramatically increases
linearity/fidelity, tape speed at 30 ips, later 15 ips
with NAB equalization; refined speeds: 7 1/2 ips, 3
3/4 ips, 1 7/8 ips

Reel-to-Reel, Magnetic Tape

1930 Electrical transcriptions Mechanical analog; electrically cut from amplified
microphone signal, high fidelity sound, lateral or
vertical grooves, horizontal or vertical stylus motion,
most discs 16" at 33 1/3 rpm

1948 Analog, with preemphasis and other equalization
(Commercial techniques (LP, RIAA); lateral grooves, horizontal
release) stylus motion; discs at 7" (most 45 rpm), 10" and 12"
(most 33 1/3 rpm)

Vinyl Record

1957 Stereophonic Vinyl Record Analog, with preemphasis and other equalization
techniques. Combination lateral/vertical stylus
motion with each channel encoded 45 degrees to the
vertical.

1962 4-Track (Stereo-Pak) Analog, 1/4 inch wide tape, 3 3/4 in/s, endless loop
cartridge.

1963 Analog, with bias, preemphasis, 0.15 inch wide tape,
17/8 in/s. 1970: introduced Dolby noise reduction.

Compact Cassette


1965 8-Track (Stereo-8) Analog, 1/4 inch wide tape, 3 3/4 in/s, endless loop
cartridge.

1969 Analog, 1/8 inch wide tape, used generally for
notetaking, mostly mono, some stereo. 2.4 cm/s or
1.2 cm/s.

Microcassette

1970 Quadraphonic 8-Track Analog, 1/4 inch wide tape, 3 3/4 in/s, 4 Channel
(Quad-8) (Q8) Stereo, endless loop cartridge.

1971 Quadraphonic Vinyl Record
(CD-4) (SQ Matrix)

1975 'Dolby Stereo' cinema surround sound

Betamax Digital Audio

1976

Elcaset

1978

Laserdisc


1982 PCM

Compact Disc (CD-DA)

1985 Audio Interchange File Format (AIFF)

1985 Sound Designer (by Digidesign)

1986 High Definition Compatible Redbook compatible physical CD containing 20-24
Digital (HDCD) bit information.

1987

Digital Audio Tape (DAT)

1991 MiniDisc (MD) ATRAC

1992 Digital Compact Cassette
(DCC)

1992 Waveforms (WAV)
Dolby Digital surround cinema sound

1993 Digital Theatre System (DTS)
Sony Dynamic Digital Sound (SDDS)

1995 MP3

1997 DVD Dolby Digital


1997 DTS-CD DTS Audio

1999 DVD-Audio

1999 Super Audio CD (SACD)

1999 Windows Media Audio (WMA)

1999 The True Audio Lossless Codec (TTA)

2000 Free Lossless Audio Codec (FLAC)

2001 Advanced audio coding (AAC)

2002 Ogg Vorbis

2003 DualDisc

2004 Apple Lossless (ALE or ALAC)

2005 HD DVD

2005 OggPCM

2006 Blu-Ray

2008 slot Music 320kb/s MP3 on microSD or microSDHC


History of Sound Recording

1. Mechanical Recording
 The first devices for recording and reproducing sound were mechanical in nature and
could not record arbitrary sounds such as the human voice.
 In 1796 a Swiss watchmaker named Smooth Nikola described his idea for what we
now call the cylinder musical box.

- Phonautograph
 1857, Edouard-Leon Scott de Martinville invented the phonautograph, the first device
to record arbitrary sound.
 Used a membrane (which vibrated in response to sound) attached to a pen, which
traced a line roughly corresponding to the sound's waveform onto a roll of paper
-Phonograph and Gramophone
 Phonograph Invented by Thomas Edison in 1877
 phonograph was a device with a cylinder covered with a hard material such as tin foil,
lead, or wax on which a stylus drew grooves
 The depth of the grooves made by the stylus corresponded to change in air pressure
created by the original sound.


 Recording could be played back by tracing a needle through the groove and
amplifying, through mechanical means, the resulting vibrations

Edison's cylinder-based Phonograph The disk-based gramophone

..Cont: Phonograph and Gramophone
 A disadvantage of the early phonographs was the difficulty of reproducing the
phonograph cylinders in mass production.
 This changed with the advent of the gramophone (phonograph in American English),
which was patented by Emile Berliner in 1887
 The gramophone imprinted grooves on the flat side of a disc rather than the outside of
a cylinder
 Instead of recording by varying the depth of the groove (vertically), as with the
phonograph, the vibration of the recording stylus was across the width of the track
(horizontally)

2. Electrical Recording
 Both phonograph cylinders and gramophone discs were played on mechanical devices
most commonly hand wound with a clockwork motor.
 The sound was amplified by a cone that was attached to the diaphragm
 The disc record fell into public favor quickly, and cylinders were not produced after
1929
 The advent of electrical recording in 1925 drastically improved the quality of the
recording process of disc records
 Electrically powered phonographs were introduced c. 1930, but crystal pickups and
electronic reproduction did not become common until the late 1930s.


 The advent of electrical recording made it possible to use microphones to capture the
sound of the performance

3. Magnetic Recording
 Magnetic recording was demonstrated in principle as early as 1898 by Valdemar
Poulsen in his telegraphone
 Magnetic wire recording, and its successor, magnetic tape recording, involve the use
of a magnetizable medium which moves with a constant speed past a recording head
 electrical signal, which is analogous to the sound that is to be recorded, is fed to the
recording head, inducing a pattern of magnetization similar to the signal
 A playback head can then pick up the changes in magnetic field from the tape and
convert it into an electrical signal.
 1932 the British Broadcasting Corporation first used a steel tape recorder for their
broadcasts

4. Recording On Film
 The first attempts to record sound to an optical medium occurred around 1900
 1906 Lauste applied for a patent to record sound on film, but was ahead of his time
 In 1923 Lee de Forest applied for a patent to record to film; he also made a number of
short experimental films, mostly of vaudeville performers
 William Fox began releasing sound-on-film newsreels in 1926, the same year that
Warner Brothers released Don Juan with music and sound effects recorded on discs,
as well as series of short films with fully synchronized sound on discs
 In 1927 the sound film The Jazz Singer was released; while not the first, it made a
tremendous hit and made the public and the film industry realize that sound film was
more than a mere novelty
 There are really two different types of synchronized film soundtrack, optical and
magnetic
 Optical sound tracks are visual renditions of sound wave forms and provide sound
through a light beam and optical sensor within the projector
 Magnetic sound tracks are essentially the same as used in conventional analog
tape recording


 In the late 1950s the cinema industry, desperate to provide a theatre experience that
would be overwhelmingly superior to television, introduced wide-screen processes
such as Cinerama, Todd-AO, and CinemaScope.
 In the 1990s, digital systems were introduced and began to prevail. Ironically, in
many of them the sound recording is, as in Vitaphone, again recorded on a separate
disk; but now, digital processes can achieve reliable and perfect synchronization

5. Digital recording
 The first digital audio recorders were reel-to-reel decks introduced by companies such
as Denon (1972), Soundstream (1979) and Mitsubishi
 Used a digital technology known as PCM recording
 Within a few years, many studios were using devices that encoded the digital audio
data into a standard video signal, which was then recorded on a U-matic or other
videotape recorder, using the rotating-head technology that was standard for video
 Similar technology was used for a consumer format, Digital Audio Tape (DAT)
which used rotating heads on a narrow tape contained in a cassette
 In the early 1990s, relatively low-priced multitrack digital recorders were introduced
for use in home studios; they returned to recording on videotape.
 The development of the MP3 audio file format, and legal issues involved in copying
such files, has driven most of the innovation in music distribution since their
introduction in the late 1990s
 At the end of the 1990s, hard disk recording became more popular

1.2 Understanding Analog and Digital Audio
Analog
 Also spelled analogue, describes a device or system that represents changing values as
continuously variable physical quantities.
 A typical analog device is a clock in which the hands move continuously around the
face
 When used in reference to data storage and transmission, analog format is that in
which information is transmitted by modulating a continuous transmission signal,
such as amplifying a signal's strength or varying its frequency to add or take away


data. For example, telephones take sound vibrations and turn them into electrical
vibrations of the same shape before they are transmitted over traditional telephone
lines
 Radio wave transmissions work in the same way. Computers, which handle data in
digital form, require modems to turn signals from digital to analog before transmitting
those signals over communication lines such as telephone lines that carry only analog
signals. The signals are turned back into digital form (demodulated) at the receiving
end so that the computer can process the data in its digital format.

Digital
 Describes any system based on discontinuous data or events
 Computers are digital machines because at their most basic level they can distinguish
between just two values, 0 and 1, or off and on. There is no simple way to represent
all the values in between, such as 0.25. All data that a computer processes must be
encoded digitally, as a series of zeroes and ones
 Digital clock is capable of representing only a finite number of times (every tenth of a
second, for example)


1.3 File Size
1. Sound file contain large amount of data and uncompress they are huge
2. A sound file generally has audio data and metadata
3. Audio data is sound that you hear
4. Metadata can include the name of the sound file, its size, duration, number of channels,
resolution or sample size (in bits), sampling rate (in kilohertz), types of compression,
information about streaming, special instruction, text or graphic.

Amplitude Type of Sound

130 dB Gunshot @5 feet

120 dB Live Rock Band @10 feet

110 dB Loud Car Stereo (interior)

90 dB Underground Train Station + The Train

80 dB A Busy Street

70 dB Vacuum Cleaner @10 feet
A Conversation @5 feet

60 dB An office cubicle

50 dB En. Alfian’s office with air-con turned off

40 dB A Whisper @5feet

30 dB Very Quiet Room

20 dB A Recording Studio


1.4 Digital Audio Format
Let us firstly look at the file formats commonly used:
1. WAV
 Developed by Microsoft (intended for Intel-based computers)
 Comes with the file extension *.wav
 16-bit wav has high sound quality, but the tradeoff is with size
 Very low compression
 8-bit wav has medium sound quality, but medium file size
2. AIFF
 Developed primarily for use on the MAC
 Come with a few extensions
 *.aif, *.aiff, *.aife
 16-bit and 8-bit AIFFs have almost similar properties with its WAV
counterpart
3. AU or MU- LAW or u-LAW
 Most prevalent on the web (platform independent) and also needs plug-in to
play
 Comes with a *.au extension
 Medium file sizes but bad sound quality (suitable for web though due to its
size)
4. MP3
 One of the best known formats around
 Achieves quite high compression rates while maintaining good sound quality
 Extension = *.mp3
 Is actually MPEG-1 Audio Layer Layer-3
 Good sound quality (with data rate of above 128 kbps that is), good
compression (only ~10% of CD-Audio)
5. RM
 Format by RealNetworks
 Extension = .ra, *.rm, *.ram
 Advantage = Real-time playability, small file size
 Disadvantage = Very not-good sound quality


6. MIDI
 MIDI as you’ve learned is very2 small in file size
 But the only thing they’re good at is producing musical-instrument-sound 
 Advantage = Small file size
 Disadvantage = Not suitable for dialogue
 Extension = *.mid, *.midi, *.kar, *.smf

REFERENCES:

Book: Vaughan T., 2004, Multimedia: Making It Work, 6th Ed, McGraw-Hill, UK.

Web: http://homepages.cwi.nl

http://en.wikipedia.org/wiki/Authoring_systems

http://www.cit.cornell.edu/atc/materials/dig/audioformats.shtml


Audio video

Recomendados

Recomendados

Más contenido relacionado

Similar a Audio video

Similar a Audio video (20)

Último

Último (20)

Audio video