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Multimedia  Contents Multimedia Graphics / Pictures Audio / Sound Video

Dec 23, 2015

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  • Slide 1
  • Multimedia Contents Multimedia Graphics / Pictures Audio / Sound Video
  • Slide 2
  • Multimedia Multimedia is: Sound Graphics Videos Multimedia applications Office documents Webpage content Movies Music Pictures
  • Slide 3
  • Multimedia Multimedia files are quite large Use compression to reduce file sizes Lossless Compression algorithms reduce size of files No information is lost Lossy Compression algorithm reduces size of files Some information is lost
  • Slide 4
  • Multimedia Trade offs between lossless and lossy compression Lossy can reduce file sizes much more Example: File compression like 7-zip Uses lossless compression If some data is lost, then file becomes corrupted Lossy compression is used in multimedia
  • Slide 5
  • Multimedia Example: 38.56666666 Lossless compression 38.56(7) Lossy compression 38.6
  • Slide 6
  • Pictures / Graphics Graphics Bitmap (BMP) - windows Graphics Interchange Format (GIF) Joint Photographic Experts Group (JPEG) Tagged Image File Format (TIFF) Portable Network Graphics (PNG) Note the abbreviations are the file extensions
  • Slide 7
  • Pictures / Graphics Digitizing Images Bit Map each image is laid out in a grid pattern Pixel - each cell in the image Pixel could be black or white Grey scale value Color The more pixels, the better the image quality Digital cameras megapixels My camera is 14.1 megapixels Each picture has 14.1 million cells that compose the pictures
  • Slide 8
  • Pictures / Graphics Bitmap of a snowman Grey Scale Bit Map Image The snowman face is a 7x7 bitmap Composed of 15, 15, 0, 0, 0, 15, 15, 15, 15, 0, 0, 0, 15, 15, 15, 0, 0, 0, 0, 0, 15, 7, 15, 3, 15, 3, 15, 7, 7, 15, 15, 7, 15, 15, 7, 7, 15, 3, 3, 3, 15, 7, 15, 7, 7, 7, 7, 7, 15 The file also contains a header containing the size of the bitmap which is 7 x 7
  • Slide 9
  • Pictures / Graphics Color Bit Map Image The top photograph is a picture with birds flying in the sky The bottom picture is one bird blown up to show pixels
  • Slide 10
  • Pictures / Graphics RGB (Red-Green-Blue) All digital images are composed of red, green and blue Usually represented by hexadecimal numbers 2 4 = 16; Numbers 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, and F Example: HTML command bgcolor =#0F69F3 bgcolor is background color Red = 0F, Green = 69, and Blue = F3
  • Slide 11
  • Pictures / Graphics RBG can make the other colors Each color has two hexademical digits or 00 FF, which ranges from 0 to 255 Each color is 2 8 and three colors 2 8 2 8 2 8 =2 24 24-bit true color We also have 32-bit color
  • Slide 12
  • Pictures / Graphics Windows BitMap Bitmaps do not use compression Bitmaps have very large file sizes Easy to calculate the file size Image is 800 x 600 with 8 bit (1 byte) color 256 color values
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  • Pictures / Graphics Calculating Image File Size (BitMap) Number of pixels = 800 x 600 = 480,000 pixels Image size = number of pixels x number of bits Image size = 480,000 pixels x 1 byte = 480,000 bytes Image size = 480,000 / 1024 = 468.75 KBytes
  • Slide 14
  • Pictures / Graphics Graphics Interchange Format (GIF) Moderately compresses images Lossless compression (simple pictures) Good for simple pictures and graphics Displays 256 colours or 8 bit Palette it chooses the best 256 colors out of 24- bit color Common for websites Animated GIFs images can display simple animation, especially for websites
  • Slide 15
  • Pictures / Graphics The animated GIF shows a four cycle gasoline engine Requires special software to create animated GIFs File size 369 kb
  • Slide 16
  • Pictures / Graphics Joint Picture Experts Group (JPEG) JPEG uses complex mathematical compression Reduces file size up to ten times that of GIF Causes lossy compression Supports True Color - 24 bit color JPEG is great for photographs Used on websites
  • Slide 17
  • Pictures / Graphics Note If the same JPEG image is re-edited, then the image can degrade If you have photos that are never edited, then leave them in JPEG If you re-edit the same photographs, then keep photo in another format PNG is good; file compression BMP is okay if you have the space; no compression
  • Slide 18
  • Pictures / Graphics Tuzla, Bosnia Picture is 858x643 True color, 32 bit or 4 bytes Bitmap = 2.2 MB I converted this to BMP and it was 2.1 MB
  • Slide 19
  • Pictures / Graphics JPEG (20%) very small file size; 34 k JPEG (95%) medium size; 212 k
  • Slide 20
  • Pictures / Graphics Portable Network Graphics (PNG) Uses loseless data compression Uses 24-bit or 32-bit color Can be used for webpages Note: 32-bit color is RBGA A is for alpha Alpha allows translucent pictures 50% alpha can see images behind the picture Windows Aero effects
  • Slide 21
  • Pictures / Graphics Creating digital pictures Scanning digitizing an image using a scanner Digital cameras Paint programs Screen capture use prtsc to capture a screen
  • Slide 22
  • Pictures / Graphics Software Create pictures by hand Microsoft Paint comes with Windows Paint,net - free Enhance photographs Microsoft Picture Editor Google Picasso Paint.net Professional Software Adobe Photoshop Adobe Illustrator Adobe Pagemaker
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  • Pictures / Graphics Conclusion For websites JPEG GIF PNG Cannot use BMP or TIFF; too large
  • Slide 24
  • Pictures / Graphics Conclusion No compression BMP TIFF Lossless compression GIF PNG Lossy compression JPEG
  • Slide 25
  • Audio / Sound Data is processed in two ways: analog or digital People generally process analog data that is continuous wave patterns. Everything we see and hear is transmitted to our eyes and ears as light and sound waves. We are equipped with analog receptors A computer is digital Two discrete states: on (or 1) and off (or 0).
  • Slide 26
  • Audio / Sound Analog and digital signals Computers: Analog to digital converters Convert analog to digital Microphone Digital to analog converters Convert digital to analog CD, MP3, etc.
  • Slide 27
  • Audio / Sound Sound cards and Modems are digital- to-analog and analog-to-digital signal converters The Wave file (.wav) used in PCs. Windows systems sounds Start up sound Many game sounds Wave files do not use compression Files are quite large
  • Slide 28
  • Audio / Sound Wave file is created by Sampling sound convertor samples the sound so many times per second CD quality is 44,100 samples per second Less sampling is lower quality Sound information is stored as bits Commonly 8, 16, or 32 bit sound file Sampling how often a sound file is read Bitrate how much information is stored per second Includes magnitude Includes how often sound is sampled
  • Slide 29
  • Audio / Sound
  • Slide 30
  • MP3 (MPEG-1 Audio Layer 3) MP3 compresses sound information Uses lossy compression Some information is lost Example: 128 kbits per second Reduces the file size of CD sound quality by 11 times Good for webpages, because file sizes are small Note many audio sound formats exist; usually for movie files
  • Slide 31
  • Audio / Sound Audio Software Audio Editing Software lets users modify audio clips and produce studio quality sound tracks. Contains equalizers, controls, etc to modify clips Rippers converts audio to different formats Windows 7 contains a music CD to MP3 ripper
  • Slide 32
  • Videos More complex Has RGB color and sound RGB is Red-Green-Blue Video has three colors and a sound Stream picture and sound change over time Requires much more information
  • Slide 33
  • Videos Frame the dimensions of a video in pixels Width x height Example: 320x120 Each picture has color 24-bit color Picture changes each second Called bit rate Bit rate 25 frames per second
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  • Videos Our video is one hour (or 3600 seconds) File size = (frame)(color)(bit rate)(time) = 320*120*24*25*3600 = 82 Giga bits = 10.4 GB Video files are always compressed Most use lossy compression Use compression to reduce size of the image of a frame Use compression to reduce the bit rate
  • Slide 35
  • Videos Frame dimensions of the video Small videos can be blown up Bit rate Important for video quality The higher the bit rate, the higher the quality Videos fast motion requires a higher bit rate Example vastly simplified
  • Slide 36
  • Videos An example of a video compression Uses three frames I-frame: The true picture P-frame: predict which pixels change B-frame: uses difference between the next frame and previous frame
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  • Videos Compressor-decompressor (CODEC) a program that encodes or decodes a streaming file Streaming file is video and/or audio Companies hold patents or copyrights for their codecs Restrictions apply
  • Slide 38
  • Videos Video files mp4Matroska (mkv) Windows (avi) Windows (wmv) Flash video (flv) Files are containers (not codec) A variety of codecs are used which are in the file MPEG2 is a codec Used for DVDs
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