Transcript Multimedia Systems: ADCS/ADIT 3

Multimedia Systems:
ADCS/ADIT 3
Image Acquisition Techniques
Image Acquisition
• Image acquisition is the process of
producing image in any multimedia system
that need the use of images.
• The first stage of any multimedia system
deal with vision system is the image
acquisition stage.
Image Acquisition
• After the image has been obtained,
various methods of processing can be
applied to the image to perform the many
different vision tasks required today.
• However, if the image has not been
acquired satisfactorily then the intended
tasks may not be achievable, even with
the aid of some form of image
enhancement
What is an image
• When you talk about an image you mean
a projection of a 3D scene into a 2D
projection plane.
What is an image
• In a very specific way an image can be
defined as a 2 variable function I(x,y) ,
where for each position (x,y) in the
projection plane, I(x,y) defines the light
intensity at this point.
What is an image
• Three types of images:
– Binary images
• I(x,y) {0 , 1}
– Gray-scale images
• I(x,y) ∈ [a , b]
– Color Images
• IR(x,y) IG(x,y) IB(x,y)
How Image is Produced
• The focus of this session is to know how
the still image can be generated by
computer.
• Still image can be generated by computer
in two ways:
– As bitmaps (or paint graphics)
– Vector-drawn (or just plain drawn) graphics.
How Image is Produced
• Bitmaps are used for photo-realistic
images and for complex drawing requiring
fine details.
• Vector-drawn objects are used for lines,
boxes, circles, polygons, and other
graphics shapes that can be
mathematically expressed in angles,
coordinates, and distances.
How Image is Produced
• The appearance of both types of images
depends on the display resolution and
capabilities of your computer’s graphics
hardware and monitor.
• Both types of images are stored in a
various file formats and can be translated
from one application to another.
• Remember to compress your acquired
image to save memory and disk space.
Important Note
• Image may be the most important element
of your multimedia project. If you are
designing multimedia put yourself into role
of graphic artist and layout designer.
Sound Acquisition
• Sound acquisition is the process of making
sound available to digital devices such as
computer.
What is Sound?
• Sound is the sensuous element of
multimedia.
• It is meaningful “speech” in any language,
from whisper to scream.
• When something vibrates in the air by
moving back and forth (such as the cone
of loud speaker), it creates waves of
pressure.
What is Sound?
• These waves spread and when they reach
your eardrums you experience the
changes of pressure, or vibrations, as
sound.
Computer Sounds
• In Windows, systems sound are WAV files,
and they reside in the Windows\Media
subdirectory.
• WAVE or WAV, short for Waveform Audio
File Format, (rarely also named Audio for
Windows) is a Microsoft and IBM audio file
format standard for storing an audio
bitstream on PCs.
Computer Sounds
• One of the available system event sounds
is Microsoft sound.wav that typically plays
when Windows starts up. Other system
event sound include start.wav and
chord.wav.
• The importance of sound (audio) toward
Multimedia projects is that it can acts as a
powerful tool that could be exploited
developing interactive multimedia
packages/systems.
Computer Sounds
• There are two general types of audio files,
which could be incorporated into
multimedia environment.
– MIDI files.
– Digitised Sound (Digital Audio).
MIDI Sound
• MIDI (Musical Instrument Digital Interface)
is a communications standard developed
in the early 1980s for electronic musical
instruments and computers.
• It allows music and sound synthesizers
from different manufacturers to
communicate with each other by sending
messages along cables connected to the
devices.
Sound Synthesizer
• A synthesizer (or synthesiser, properly
"sound" or "music" synthesizer, often
abbreviated to "synth") is an electronic
instrument that utilizes multiple sound
generators to create complex waveforms
that can be combined into countless sonic
variations through various waveform
synthesis techniques.
Sound Synthesizer
• Synthesizers are often controlled with a piano-style
keyboard, leading such instruments to be referred to
simply as "keyboards.
MIDI Sound
• MIDI provides a protocol for passing
detailed descriptions of a musical scores,
such as the notes, sequence of notes, and
what instruments will play these notes.
• MIDI does not digitised sound.
• A MIDI file is a list of commands that are
recordings of musical actions that when
send to playback device, results in sound.
MIDI Sound
• A MIDI file is smaller compared to digital
data.
Digital Sound
• Refers to the reproduction and
transmission of sound stored in a digital
format. This includes CDs as well as any
sound files stored on a computer.
• In sound recording and reproduction
systems, digital audio refers to a digital
representation of the audio waveform for
processing, storage or transmission.
Digital Sound
• Digital audio data (digital sound) could be
created from a a microphone, a
synthesizer, CD player or even from a TV
broadcast.
• In contrast to MIDI data, digital audio is the
actual representation of sound, stored in
the forms of thousands individual numbers
called ‘samples’.
Digital Sound
• Digital sound is used for music CDs.
• The key differences between digital audio
and MIDI data is that MIDI sounds play
only in MIDI devices. On other hand digital
sound can play on any playback system.
Digital Sound
• Digital audio is used far more than MIDI
because when used in any audio track, will
play as good in the end as it did in the
beginning when was created.
• Two additional reason to work with digital
audio:
– A wider selection of application software and
system support for digital audio is available
for different platforms.
Digital Sound
– The preparation and programming required
for creating digital audio do not demand a
knowledge of music theory, working with MIDI
data usually does require modicum of
familiarity with musical scores, keyboards,
and notation as well as audio production.
Digital Sound
• Preparing digital sound file include
converting analog recorded materials from
casette tapes etc, into digitised data that
can be read by computer.
• In most cases this means playing sound
from one device (such as a tape recorder)
right into the computer using appropriate
audio digitizing software.
Digital Sound
• Two crucial aspects of preparing digital
audio files:– Balancing the need for sound quality with your
available RAM and hard disk.
– Setting a proper recording level to get a good,
clean recording.
• Note
“The higher the sound quality, the larger
your file will be”