cs1101_09A_lec07 - CS1101 Lec07 Digital Media Dr Jiying...

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CS1101 Lec07   Digital Media Dr. Jiying Wang Semester A, 2009-10 Computer Science Department City University of Hong Kong
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CS1101 - Lec07 2 Objectives Describe the various types of digit media List the hardware/software that can be used to work with various types of  digital media Identify digit media files by their file extensions Compare waveform audio and MIDI music Compare bitmap images and vector images, and describe procedures required to  convert vector graphics to into bitmaps, and convert bitmaps to vector graphics Explain how resolution, image size, color depth and compression affect the file  size of a bitmap image
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CS1101 – Lec07 3 Objectives (cont'd) Illustrate some commonly used image compression techniques Use storage calculation to justify the reason why compression is essential for  digital video Explain how window size, frame rate, and compression affect file size for a  desktop video Describe how video streaming works
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CS1101 - Lec07 4 For you to practice after class Lec07-Q1:  what is the compression ratio  when compressing a CD song into the MP3  format with 128 kbit/s bit rate? (assuming 1k=10 3 ) Lec07-Q2:  similar to audio, uncompressed video data need a large amount of storage space.   F or a 30 seconds clip in PAL DVD format with stereo sound in a sample rate of 48 kHz,  how many bytes are needed ? (assuming 1k=10 3 ) Lec07-Q3:  similar to audio, video compression can also be described in  bit rate  - the number  of data bits per second. If we know that MPEG-2 codec in a DVD player has a bit rate  up to 9.8 Mb/s (assuming 1M = 10 6 ), what is the compression ratio  if the clip in above  question is compressed in MPEG-2? 
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CS1101 – Lec07 5 Digital Media Digital media Pictures, sound, video and animation stored/processed in computers in digital format  (i.e., binary numbers) Typical hardware requirements  work with digital media A powerful microprocessor Large memory and storage capacity A high-quality monitor and a display card A CD-ROM or DVD-ROM drive May also need some input devices - A microphone or keyboard for audio input - A digital camera or scanner for graphics input  - An analog video camera for video input and a video capture card to convert analog video  to digital video - Or a digital video camera
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Lec07 - Digital Media - Digital Sound
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CS1101 – Lec07 7 Digital Audio Basics Audio is originally an  analog  waveform signal, and it must be converted into  discrete digital  signal in order to be stored in and processed by computers Example converting devices Analog->digital : sound cards, display/video cards, scanners,
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This note was uploaded on 03/10/2012 for the course CS 1101 taught by Professor Drxue during the Spring '11 term at City University of Hong Kong.

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cs1101_09A_lec07 - CS1101 Lec07 Digital Media Dr Jiying...

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