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Understanding Digital Media

Understanding Digital Media. Smaller. Better. Digital From Scarcity to Abundance. Faster. Cheaper. The Language of Digital : Bits & Bytes. Bit Binary Digit The smallest data unit A single one or zero Typically 8-bits make up a byte . An 8-bit system has 256 discrete values.

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Understanding Digital Media

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  1. Understanding Digital Media

  2. Smaller Better Digital From Scarcity to Abundance Faster Cheaper

  3. The Language of Digital : Bits & Bytes • Bit • Binary Digit • The smallest data unit • A single one or zero • Typically 8-bits make up a byte. • An 8-bit system has 256 discrete values.

  4. More bits = More colors = More information

  5. Digitizing or Capturing • Pixels • Pixel is Short For Picture Element • A Pixel is the Smallest Unit of Video Information. • Each Pixel is made up of a Red, Green and Blue Dot Analog Digitizing Card Digital

  6. Bit Depth/Pixel Depth • Bit Depth • The Number of Bits Stored with Each Pixel (Sometimes Called Pixel Depth) • The Higher the Pixel Depth, The Greater the Number of Colors Available 8-Bit Pixel Depth: 28 = 256 Colors 16-Bit Pixel Depth: 216 = 65,536 Colors 24-Bit Pixel Depth: 224 = 16,777,216 Colors

  7. Full-Color Video • Uses 24-Bit Pixel Depth • Each Pixel Gets 24-Bits or 3-Bytes of Information.

  8. Screen SizeDigital video can be stored & displayed in different screen sizes. • 640 X 480 = "Full Screen Video"Out of TV's 525 Lines, Only 480 are Used for the Picture • 320 X 240 • sometimes Called Quarter Screen (More Accurately 1/2 Screen) • 160 X 120 • 320 X 240 and 160 X 120 Tend to Be Used on the World Wide Web and CD-ROMs. • Larger Screen Size Takes More Storage Space

  9. Storage • Full-Screen: 640 X 480 Pixels Each Frame • Full-Color: 3-Bytes Per Pixel (24-Bit Display) • Full-Motion: 30 Frames Per Second

  10. Sound • Sound is Frequency & Amplitude • Frequency is No. of Waves Over Time (Pitch) • Amplitude is Height of Wave (Volume)

  11. Digitizing Audio • To Describe a Wave With Numbers • Referred to as Sampling Note: We Took 8 Samples in 1-Second

  12. Digitizing Audio • Data Can Be Put in a Table

  13. Problem is … To Accurately Represent the Original Sound, You Must Sample Often.

  14. Sampling Rate • The Number of Times Per Second a Sample is Taken. • CD-Audio is Sampled 44,100 Times Per Second (44.1 KHz) • A Computer Checks the Analog Wave 44,100 Times Per Second. • This Many Samples Will "Accurately" Represent the Original. • More Samples Means More Computer Storage Needed.

  15. Sample Size • Quantization • A Measurement of How Precise You Want to Measure Each Sample. • This is a Measurement of Volume (or Power). • The More Increments of Measurement, the More Accurate the Representation of the Wave • CD-Quality Uses 16-Bits For Each Sample. • The Computer Stores 16-Bits (2 Bytes) For Each Sample. • 16-Bits is 65,536 Increments

  16. CD-Quality Audio    Uses 44,100 Samples Per Second    Uses 16-Bits For Each Sample • 44,100 Samples Each Second • 2-Bytes (16-Bits) Per Sample • 2-Channels (Stereo)

  17. One Minute of Video Would Take Up 1.68 GigaBytes • 30 Minutes of Video Would Take Up 50.4 GigaBytes • Hard Drives Can Only Transfer About 5 MegaBytes Per sec. • There Must Be a Better Way!

  18. Compression • Why compress? • Storage costs • Communication Bandwidth • There will never be enough bandwidth. • Super High Definition format (2,048 X 2,048 pixels) - 14 times as large as NTSC. • Quality Improvement • Video can create a bottleneck and everything has to slow down. • It improves the picture you can achieve in the bandwidth you have.

  19. How Compression Works • Lossless Compression: Shrinking Without Losing Any Information • Lossy Compression: Shrinking With Some Loss of Information

  20. Compression Types • IntraFrame Compression • Compressing an Individual Frame of Video • Spatial Compression • Compression Designed for Still Images • Variable Amounts of Compression • Frames With Lots of Similar Adjacent Pixels Compress Best • InterFrame Compression • Looking at Changes From One Frame to the Next to See Which Pixels Are the Same • Temporal Compression • Compression Specifically for Moving Video • Looks at Adjacent Frames to See Which Pixels Are the Same

  21. No Compression (Simplified) Data is Stored for Each Pixel

  22. Lossless Intraframe Compression • Adjacent Duplicate Pixels Can be Done in Shorthand • Less Data Needs to Be Stored

  23. Lossy INTRAframe Compression • Takes an Average for Vertical Pairs

  24. Interframe Compression • Each Key Frame Has No Compression • Frame 1 is the Key Frame • The Next Frames are Compared to the Previous Frame • Only Data for the Differing Pixels Needs to Be Stored • An Excellent System for Moving Video

  25. Interframe Compression

  26. GOP (Group of Picture) I : Intra-coded Frame P : Previous I Frame B : Bi-directionally predicted frame

  27. Motion Picture Experts Group (MPEG) • The most widely used group of standards for audio and video. • MPEG-1 • Coding of moving pictures and associated audio for digital storage media at up to about 1.5 Mbps • - VHS quality / CD-Rom • MPEG-2 • high data rate of 2 – 15 Mbps • commercial satellite and cable delivery of digital TV • MP@ML: Compression Standard for HDTV

  28. MPEG-4 • data rate between 5 kbps and 2Mbps • Very Low Bitrate Video (VLBV) : 5 kbps – 64 kbps • High Bitrate Video (HBV) : 64kbps – 2 MBPS • more advanced , object oriented, interactive functions • Version 2 adds profiles for intellectual property management, a file format, integration of Java code, 3D coding, and text-to-speech markup language. • MPEG-7 • not a compression scheme at all • “Multimedia Content Description Interface” • a standard set of descriptors for multimedia information that will permit scene motion and visual content searches

  29. MPEG AUDIO Three coding techniques: Layer-1, Layer-2, and Layer-3 Layer-1 To produce CD quality audio, it requires 384 Kbps. Layer-3 It requires only 112 Kbps. It is also capable of further reducing bandwidth (and quality) of the audio signal from 128 Kbps (best quality) all the way down to 8 Kbps (telephone quality) with several steps in between 96, 56, 32, and 16 Kbps.

  30. What is Digital Media Revolution? • It started with the personal computer and streaming media over the Internet or corporate network. • The versatility of digital media stems from their ability to represent, manipulate, and store information and entertainment electronically in binary devices. • This provided for the first time, truly interactive, on-demand audio and video. • Digital mediarevolution has changed the ways how news, information, and entertainment is distributed and experienced. • Digital media revolution is now extending beyond the PC • It guarantees anywhere, anytime access to the information and entertainment users demand.

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