Transcript Dasar-Dasar Multimedia

Pengantar Multimedia
Sound
Physical phenomenon – vibration.
 Source = electrical – acoustic
 Vibration – oscillation – wave
 Wave
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 periodical – song, musical instrument
 non periodical – explosion, cough
Vibration
Diff Air
pressure
Travels through
medium
Receptor
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Periodical – has the same pattern over a
certain interval
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Speed of sound
 depends on the medium that the waves pass
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through
depends on the property of a material
Air, sea level, 20° = 343m/s (most common)
Water, 20° = 1,482 m/s
Steel = 5.960 m/s
Frequency
The amount of period in 1s.
 Hertz / cycles per second (cps)
 Wavelength = sound speed (c) /
frequency (f)
 eg. A wave of 20 kHz with 343m/s has
17.15 wavelength.
 343/20 = 17,15.
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Based on the frequency
 Infrasound
 Audible Sound
 Ultrasound
 Hypersound
0 Hz
20 Hz
20 KHz
1 GHz
- 20 Hz
- 20 KHz
- 1 GHz
- 10 THz
Sound created by human = 50 Hz – 10KHz
 Musical Sound = 20 Hz – 20 KHz
 Multimedia system must use audible sound.

Audible sound is called Audio and the wave
is called Acoustic Signal.
 In connection to Audio, all sound frequencies
except Audio is called Noise.
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ADC
Device that converts a continuous
physical quantity (usually voltage) to a
digital number that represents the
quantity's amplitude.
 Digital sampling : Measuring the analog
signal at regular intervals. Eg. Audio CD
with 44100Hz has sample of 44100/s.
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Application
 Music Recording. Current ADC converter can
sample at rates up to 192KHz.
 DSP (Digital signal processing). TV tuner cards
use fast ADC. Slow ADC might be used in 8, 10,
12, or 16-bit microcontrollers.
 Digital Imaging, uses ADC to converts colors into
data stream.
DAC
Converts digital data (usually binary)
into an analog signal (current, voltage,
or electric charge).
 Unlike analog signals, digital data can
be transmitted, manipulated, and stored
without degradation, albeit with more
complex equipment.
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Application
 Audio = Most modern audio signals are
stored in digital form (MP3, MP4), so we
need CD Player, Digital Music Player, PC
sound cards. In VoIP (Voice over IP)
applications, the source must first be
digitized for transmission, so it undergoes
conversion via an analog-to-digital
converter, and is then reconstructed into
analog using a DAC on the receiving party's
end.
Audio Format Development
Audio File
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.3gp = multimedia container format can contain
proprietary formats
.act = ACT is a lossy 8 Kbit/s compressed audio
format recorded by most Chinese MP3 and MP4
players with a recording function, and voice
recorders.
.aiff = standard audio file format used by Apple. It
could be considered the Apple equivalent of wav.
.aac = the Advanced Audio Coding format is based
on the MPEG-2 and MPEG-4 standards.
.amr = AMR-NB (adaptive Multi Rate – Narrow
Band) audio, used primarily for speech.
.ape = Monkey's Audio lossless audio compression
format.
 .au = the standard audio file format used by Sun, Unix
and Java.
 .awb = AMR-WB audio, used primarily for speech.
 .dct = A variable codec format designed for dictation. It
has dictation header information and can be encrypted
(as may be required by medical confidentiality laws).
 .dss = Olympus proprietary format (old and poor).
 .dvf = a Sony proprietary format for compressed voice
files; commonly used by Sony dictation recorders.
 .flac = File format for the Free Lossless Audio Codec, a
lossless compression codec.
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.gsm = designed for telephony use in Europe with very
practical format for telephone quality voice.
.iklax = An iKlax Media proprietary format, a multi-track
digital audio format allowing various actions on
musical data, for instance on mixing and volumes
arrangements.
.ivs = developed by 3D Solar UK Ltd for use in music
downloaded from their Tronme Music Store and
interactive music and video player.
.m4a = MPEG-4 audio, used by Apple for unprotected
music downloaded from their iTunes Music Store
.m4p = version of AAC with DRM developed by Apple
for use in music downloaded from their iTunes Music
Store.
.mmf = a Samsung audio format that is used in
ringtones.
 .mp3 = MPEG Layer III Audio. Is the most common
sound file format used today.
 .mpc = Musepack (formerly known as MPEGplus,
MPEG+ or MP+) is an open source lossy audio codec.
 .msv = a Sony proprietary format for Memory Stick
compressed voice files.
 .ogg = .oga (rare) = a free, open source container
format supporting a variety of formats, the most
popular of which is the audio format Vorbis. Vorbis
offers compression similar to MP3 but is less popular.
 .Opus = a lossy audio compression format developed
by the Internet Engineering Task Force (IETF).
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.ra = .rm = a RealAudio format designed for streaming
audio over the Internet.
.raw = a raw file can contain audio in any format but it
is rarely used except for technical tests.
.sln = Signed Linear format used by Asterisk.
.tta = The True Audio, real-time lossless audio codec.
.vox = the vox format most commonly uses the Dialogic
ADPCM (Adaptive Differential Pulse Code Modulation)
codec.
.wav = standard audio file container format used mainly
in Windows PCs. Commonly used for storing
uncompressed (PCM), CD-quality sound files, which
means that they can be large in size—around 10 MB
per minute.
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.wma = Windows Media Audio format, created by
Microsoft. Designed with Digital Rights Management
(DRM) abilities for copy protection.
.wv = format for wavpack file.
.webm = Royalty-free format created for HTML5 video.
MIDI
Musical Instrument Digital Interface.
 A protocol that enables computers,
synthesizers, keyboards, and other
musical devices to communicate with
each other.
 Small file size.
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