Introduction to Digital Libraries Digital Data (2)

1. Introduction to Digital LibrariesDigital Data (2)

2. Data Music

3. Why digitize audio? • 100 years of data on a Wide variety of unstable media • Wide variety of playback mechanism

4. Analog to Digital Recording Chain ADC Microphone converts acoustic to electrical energy. It’s a transducer. Continuously varying electrical energy is an analog of the sound pressure wave. ADC (Analog to Digital Converter) converts analog to digital electrical signal. Digital signal transmits binary numbers. DAC (Digital to Analog Converter) converts digital signal in computer to analog for your headphones.

5. Wire Recordings • Time Frame • The 1930s and '40s • Technology • Magnetized wire • Use • Field correspondents used portable versions in World War Two. Their repair kits included extra wire, grips and a soldering iron.

6. Acetate tape • Time Frame • Introduced in the early 1950s • Widely in use during 1960s • Technology • Magnetic signal on acetate tape • curls, shrinks and loses mass over time. • Does not stretch or deform but breaks easily • Uses • Home recording • Archiving older recording • Broadcast radio recording

7. Polyester tape • Time Frame • 1970s • Technology • Magnetic signal on polyester tape • Excellent sound fidelity • Polyester tape deforms (stretches) easily • Restored by gentle heating in the so-called "easy bake" oven • Uses • Home recording • Archiving older recording • Broadcast radio recording

8. Digital Audio Basics • Bit Depth • Bit Rate • Sampling Rate • Frequency • Equalization • Sound Scrubbing

9. Bit Depth In digital audio, bit depth describes the potential accuracy of a particular piece of hardware or software that processes audio data.

10. Binary representation • 16 bits can represent 65,536 possible speaker cone or microphone diaphragm positions (possible levels). This is enough for very high quality audio • The current maximum resolution used is 24 bits. This equates to 16,777,216 positions. nobody has manufactured a converter accurate to more than 24 bits.

11. Bit Rate • In general, describes the data transfer rate • In digital audio, describes the kilobits per second (kbs) in your file • Standard MP3 file has 128 kbs • Very high quality audio has 320 kbs

12. Frequency • The number of vibrations in a sound wave per unit of time (Spectrum of sound). • Measured in hertz (Hz)

13. Equalization • In audio processing, equalization (EQ) is the process of modifying the frequency envelope of a sound. • The frequencies are controlled by bands (ranges of frequencies) • Controls the overall quality of the sound

14. Sampling Rate The number of times per second the program converting the analog to digital records the sound. • CD sampling rate is 44.1 kHz • Higher rates - 88.2 kHz, 96 kHz, and 192 kHz. • Telephone speech is sampled at 8 kHz.

15. Synthesis • Audio synthesis is the art and science of generating audio signals. • A synthesiser is an electronic instrument capable of producing musical sounds

16. Audio Formats • Emerging Archival Standards • AIFF – Audio Interchange File Format • BWF – Broadcast Wave Format • Delivery formats • Real – proprietary streaming protocol • MP3 – the standard • MPEG4 – multimedia streaming standard

17. Data GIS and Maps

18. GIS Defined In the strictest sense, a GIS is a computer system capable of assembling, storing, manipulating, and displaying geographically referenced information, i.e. data identified according to their locations. Practitioners also regard the total GIS as including operating personnel and the data that go into the system.

19. Data for a GIS comes in three basic forms: • Spatial data -What Maps are Made Of • Spatial data, made up of points, lines, and areas, is at the heart of every GIS. Spatial data forms the locations and shapes of map features such as buildings, streets, or cities.   • Tabular data—adding information to mapsTabular data is information describing a map feature. For example, a map of customer locations may be linked to demographic information about those customers.   • Image data—using images to build mapsImage data includes such diverse elements as satellite images, aerial photographs, and scanned

20. Is it 'spatial' or 'geographic'? • 'geographic' has to do with the Earth • its two-dimensional surface • its three-dimensional atmosphere, oceans, sub-surface • 'spatial' has to do with any multi-dimensional frame • medical images are referenced to the human body • engineering drawings are referenced to a mechanical object • architectural drawings are referenced to a building

21. Enter GIS • A computer-based tool for holding, displaying, and manipulating huge amounts of spatial data.

22. GIS Basics • Points • Lines • Polygons • Layers • Features • Attributes • Basic Set math • Unions • Intersections

23. Different Maps for Different Functions U.S. Geological Survey (USGS) digital line graph (DLG) data of roads. USGS DLG of rivers. USGS digital elevation (DEM). USGS DLG of contour lines (hypsography).

24. GIS Basics Builds relationships between data by geographic location •  x, y and z coordinates • Latitude, Longitude  • ZIP code • Highway marker • Other control identifiers

25. Global Positioning Systems • GPS is a constellation of 27 satellites (31+/- Satellites orbiting the earth) orbiting the earth which send signals to GPS receiver on earth. • The receiver measures the travel time of signals transmitted from at least three satellites. The receiver calculates its distance from the satellite.

26. HOW TO GET A POSITION • Need signal from at least four SVs for 3D position • One SV provides a time reference • Distance to three remaining SVs is determined by observing the GPS signal travel time from SV to the receiver • With three known points, and distances to each, we can determine the GPS receiver’s position (trilateration)

27. Concept of Vector and Raster Real World Raster Representation Vector Representation point line polygon

28. area is covered by grid with (usually) equal-sized cells location of each cell calculated from origin of grid: “two down, three over” cells often called pixels (picture elements); raster data often called image data attributes are recorded by assigning each cell a single value based on the majority feature (attribute) in the cell, such as land use type. easy to do overlays/analyses, just by ‘combining’ corresponding cell values: “yield= rainfall + fertilizer” (why raster is faster, at least for some things) simple data structure: directly store each layer as a single table (basically, each is analagous to a “spreadsheet”) computer data base management system not required (although many raster GIS systems incorporate them) 0 1 2 3 4 5 6 7 8 9 1 1 1 1 1 4 4 5 5 5 0 1 1 1 1 1 4 4 5 5 5 1 1 1 1 1 1 4 4 5 5 5 2 1 1 1 1 1 4 4 5 5 5 3 1 1 1 1 1 4 4 5 5 5 4 2 2 2 2 2 2 2 3 3 3 5 2 2 2 2 2 2 2 3 3 3 6 2 2 2 2 2 2 2 3 3 3 7 2 2 4 4 2 2 2 3 3 3 8 2 2 4 4 2 2 2 3 3 3 9 corn fruit wheat clover fruit Representing Data using Raster Model oats

29. Full Matrix--162 bytes 111111122222222223 111111122222222233 111111122222222333 111111222222223333 111113333333333333 111113333333333333 111113333333333333 111333333333333333 111333333333333333 1,7,2,17,3,18 1,7,2,16,3,18 1,7,2,15,3,18 1,6,2,14,3,18 1,5,3,18 1,5,3,18 1,5,3,18 1,3,3,18 1,3,3,18 Raster Data StructuresRunlength Compression (for single layer) Run Length (row)--44 bytes This is a “lossless” compression, as opposed to “lossy,” since the original data can be exactly reproduced. Now, GIS packages generally rely on commercial compression routines. Pkzip is the most common, general purpose routine. MrSid (from Lizard Technology)and ECW (from ER Mapper) are used for images. All these essentially use the same concept. Occasionally, data is still delivered to you in run-length compression, especially in remote sensing applications. “Value thru column” coding. 1st number is value, 2nd is last column with that value.

30. Applications • Military (DoD) – civilian uses now exceed military • Space Travel (NASA) • Survey, Mapping & GIS • Resource and Asset Management • Environmental & Forestry • Mining, Oil & Gas • Agriculture • Utilities & Construction • Transportation • Vehicle Security (Fleet Management) • Public Safety • Emergency Management, Search & Rescue • Crime Prevention • Timing & Synchronization • (banking, telecommunications) • LBS - Location Based Services • (cell phones, wireless web) Precision Construction & Agriculture Solar GPS Cattle Herder (noise or electric shock)

31. Other Applications… • Tracking Systems • - Pet Collar • - Teddy Bears, Backpacks • - Implants… Xega injectable GPS chip ($4,000 + $350/month) Mexico (requires additional wearable accessory) GTX Ambulator (Alzheimer’s GPS Shoes) (tracking and geo-fence) Nano GPS tracker ($200 + $45/month), panic button, for people or nativity scenes… Pet collars Web or cell connection Virtual/Geo-Fence Garmin Astro Pet Tracker (communicates with base unit)

32. The Future… Does GPS make a dumber…? Driver follows GPS directions onto train tracks… GPS directions send Mercedes downstream… Trucker drives past sign, becomes wedged in small farm lane… Bus driver follows GPS directions, ignores signs, plows into overpass…

33. GIS Metadata FGDC – the Metadata Standard for GIS • Federal Geographic Data Committee • Under the auspices of the U.S. Geological Survey • They refer to the standard as Content Standard for Digital Geospatial Metadata (CSDGM) • Spatial Data Transfer Standard (SDTS) is for transferring digital spatial data sets between spatial data software.

34. Digital Video

35. Video • Video comes from a camera, which records what it sees as a sequence of images • Image frames comprise the video • Frame rate = presentation of successive frames • minimal image change between frames • Frequency of frames is measured in frames per second [fps]. • Sequencing of still images creates the illusion of movement • > 16 fps is “smooth” • Standards: 29.97 is NTSC, 24 for movies, 25 is PAL, 60 is HDTV

36. Mechanical Television

37. The Video Data Firehose • To play one SECOND of uncompressed 16-bit color, 640 X 480 resolution, digital video requires approximately 18 MB of storage. • One minute would require about 1 GB. Without compression, digital video would not be possible with current storage technology.

38. Data Reduction through Scaling • The easiest way to save memory is to store less, e.g. through size scaling. Original digital video standards only stored a video window of 160 X 120 pixels. A reduction of 1/16th the size of a 640 X 480 window. A 320 X 240 digital video window size is currently about standard, yielding a 4 to 1 data reduction. • A further scaling application involves time instead of space. In temporal scaling the number of frames per second (fps), is reduced from 30 to 24.

39. Frame Compaction • The individual frames (intraframe compression) is a sequence of three standard text file compression schemes. Run-length encoding (RLE), Huffman coding, and arithmetic coding. • RLE replaces sequences of identical values with the number of times the value occurs followed by the value (e.g., 11111000011111100000 ==>> 51406150). • Huffman coding replaces the most frequently occurring values|strings with the smallest codes.

40. Interframe Compression (MPEG style) • Interframe compression takes advantage of minimal changes from one frame to the next to achieve dramatic compression. Instead of storing complete information about each frame only the difference information between frames is stored.

41. MPEG: Motion Picture Experts Group • MPEG-1 (1992) • Compression for Storage • 1.5Mbps • Frame-based Compression • MPEG-2 (1994) • Digital TV • 6.0 Mbps • Frame-based Compression • MPEG-4 (1998) • Multimedia Applications, digital TV, synthetic graphics • Lower bit rate • Object based compression • MPEG-7 • Multimedia Content Description Interface, XML-based • MPEG-21 • Digital identification, IP rights management

42. HDTV • 2x horizontal and vertical resolution • SDTV: 480 line, 720 pixels per line, 29.97 frames per second • x 16 bits/pixel = 168 Mbits/sec uncompressed • HDTV: expanded to 1080 lines, 1920 pixels per line, 60 fps • x 16 bits/pixel = 1990 Mbits/sec uncompressed • HDTV Audio Compression is based on the Dolby AC-3 system with sampling rate 48kHz and perceptually coded

43. Comparison Current TV HDTV

44. Original Timeline of HDTV • First began in 60’s at NHK, the Japan Broadcasting Corporation. • In 1993, FCC suggested an alliance that could create the best possible system • November 1998: HDTV transmissions begin at 27 stations in the top 10 markets • November 1999: digital broadcasts in the next 20 largest markets • May 2002: remaining commercial stations must convert • 2003: public stations must convert to digital broadcasts • 2004: stations must simulcast at least 75% of their analog programming on HDTV • 2005: stations must simulcast 100% of their analog programming • 2006: stations relinquish their current analog spectrum • NTSC TV sets will no longer be able to pick up broadcast signals

45. Interleaver Stream Graph

46. Trellis Encoding • In HDTV, the trellis encoder is a convolution encoder followed by a symbol mapper. • This provides good noise immunity (somehow) • HDTV encoder uses 12 trellis coders in parallel

47. Convolution Encoding • Input is an m bit symbol • Output is an n bit symbol • m/n is the rate (HDTV uses 2/3) • K is the reach: the number of output symbols that each input symbol affects (HDTV has K=3)

48. Trellis Encoding (cont.) • Trellis Encoder used in HDTV “pre-coder” “ungerboeck encoder” Source: ATSC standard A53, revision b

49. Trellis Encoding (cont.) • 12 Trellis Encoders Source: ATSC standard A53, revision b

50. Comparison (current TV)