Multimedia Systems: ADCS/ADIT 3

1. Multimedia Systems: ADCS/ADIT 3 Image Acquisition Techniques

2. 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.

3. 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

4. What is an image • When you talk about an image you mean a projection of a 3D scene into a 2D projection plane.

5. 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.

6. 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)

7. 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.

8. 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.

9. 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.

10. 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.

11. Sound Acquisition • Sound acquisition is the process of making sound available to digital devices such as computer.

12. 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.

13. What is Sound? • These waves spread and when they reach your eardrums you experience the changes of pressure, or vibrations, as sound.

14. 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.

15. 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.

16. Computer Sounds • There are two general types of audio files, which could be incorporated into multimedia environment. • MIDI files. • Digitised Sound (Digital Audio).

17. 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.

18. 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.

19. Sound Synthesizer • Synthesizers are often controlled with a piano-style keyboard, leading such instruments to be referred to simply as "keyboards.

20. 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.

21. MIDI Sound • A MIDI file is smaller compared to digital data.

22. 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.

23. 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’.

24. 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.

25. 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.

26. 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.

27. 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.

28. 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”