3 Why digitize audio?100 years of data on a Wide variety of unstable mediaWide variety of playback mechanism
4 Analog to Digital Recording Chain ADCMicrophone 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 Technology Use The 1930s and '40s Magnetized wireUseField correspondents used portable versions in World War Two. Their repair kits included extra wire, grips and a soldering iron.
6 Acetate tape Time Frame Technology Uses Introduced in the early 1950s Widely in use during 1960sTechnologyMagnetic signal on acetate tapecurls, shrinks and loses mass over time.Does not stretch or deform but breaks easilyUsesHome recordingArchiving older recordingBroadcast radio recording
7 Polyester tape Time Frame Technology Uses 1970s Magnetic signal on polyester tapeExcellent sound fidelityPolyester tape deforms (stretches) easilyRestored by gentle heating in the so-called "easy bake" ovenUsesHome recordingArchiving older recordingBroadcast radio recording
8 Digital Audio Basics Bit Depth Bit Rate Sampling Rate Frequency EqualizationSound Scrubbing
9 Bit DepthIn 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 audioThe 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 fileStandard MP3 file has 128 kbsVery high quality audio has 320 kbs
12 FrequencyThe number of vibrations in a sound wave per unit of time (Spectrum of sound).Measured in hertz (Hz)
13 EqualizationIn 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 RateThe number of times per second the program converting the analog to digital records the sound.CD sampling rate is 44.1 kHzHigher rates kHz, 96 kHz, and 192 kHz.Telephone speech is sampled at 8 kHz.
15 SynthesisAudio synthesis is the art and science of generating audio signals.A synthesiser is an electronic instrument capable of producing musical sounds
18 GIS DefinedIn 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 OfSpatial 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 maps Tabular 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 maps Image data includes such diverse elements as satellite images, aerial photographs, and scanned
20 Is it 'spatial' or 'geographic'? 'geographic' has to do with the Earthits two-dimensional surfaceits three-dimensional atmosphere, oceans, sub-surface'spatial' has to do with any multi-dimensional framemedical images are referenced to the human bodyengineering drawings are referenced to a mechanical objectarchitectural drawings are referenced to a building
21 Enter GISA computer-based tool for holding, displaying, and manipulating huge amounts of spatial data.
22 GIS Basics Points Lines Polygons Layers Features Attributes Basic Set mathUnionsIntersections
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 coordinatesLatitude, Longitude ZIP codeHighway markerOther 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 POSITIONNeed signal from at least four SVs for 3D positionOne SV provides a time referenceDistance to three remaining SVs is determined by observing the GPS signal travel time from SV to the receiverWith 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 Representationpointlinepolygon
28 Representing Data using Raster Model area is covered by grid with (usually) equal-sized cellslocation of each cell calculated from origin of grid:“two down, three over”cells often called pixels (picture elements); raster data often called image dataattributes 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)cornwheatfruitcloveroats123456789
29 Raster Data Structures Runlength Compression (for single layer) Full Matrix--162 bytes1,7,2,17,3,181,7,2,16,3,181,7,2,15,3,181,6,2,14,3,181,5,3,181,3,3,18Run Length (row)--44 bytesThis 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 islast column with that value.
30 Applications Military (DoD) – civilian uses now exceed military Space Travel (NASA)Survey, Mapping & GISResource and Asset ManagementEnvironmental & ForestryMining, Oil & GasAgricultureUtilities & ConstructionTransportationVehicle Security (Fleet Management)Public SafetyEmergency Management, Search & RescueCrime PreventionTiming & Synchronization(banking, telecommunications)LBS - Location Based Services(cell phones, wireless web)Precision Construction& AgricultureSolar GPS Cattle Herder(noise or electric shock)
31 Other Applications… - Pet Collar - Teddy Bears, Backpacks - Implants… Tracking Systems- Pet Collar- Teddy Bears, Backpacks- Implants…Xega injectable GPS chip($4,000 + $350/month)Mexico (requires additionalwearable 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 collarsWeb or cell connectionVirtual/Geo-FenceGarmin 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 smallfarm lane…Bus driver follows GPS directions, ignores signs, plows into overpass…
33 GIS Metadata FGDC – the Metadata Standard for GIS Federal Geographic Data CommitteeUnder the auspices of the U.S. Geological SurveyThey 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.
35 VideoVideo comes from a camera, which records what it sees as a sequence of imagesImage frames comprise the videoFrame rate = presentation of successive framesminimal image change between framesFrequency of frames is measured in frames per second [fps].Sequencing of still images creates the illusion of movement> 16 fps is “smooth”Standards: is NTSC, 24 for movies, 25 is PAL, 60 is HDTV
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 CompactionThe 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., ==>> ).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 Compression for Storage1.5MbpsFrame-based CompressionMPEG-2 (1994)Digital TV6.0 MbpsMPEG-4 (1998)Multimedia Applications, digital TV, synthetic graphicsLower bit rateObject based compressionMPEG-7Multimedia Content Description Interface, XML-basedMPEG-21Digital identification, IP rights management
42 HDTV 2x horizontal and vertical resolution SDTV: 480 line, 720 pixels per line, frames per secondx 16 bits/pixel = 168 Mbits/sec uncompressedHDTV: expanded to 1080 lines, 1920 pixels per line, 60 fpsx 16 bits/pixel = 1990 Mbits/sec uncompressedHDTV Audio Compression is based on the Dolby AC- 3 system with sampling rate 48kHz and perceptually coded
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 systemNovember 1998: HDTV transmissions begin at 27 stations in the top 10 marketsNovember 1999: digital broadcasts in the next 20 largest marketsMay 2002: remaining commercial stations must convert2003: public stations must convert to digital broadcasts2004: stations must simulcast at least 75% of their analog programming on HDTV2005: stations must simulcast 100% of their analog programming2006: stations relinquish their current analog spectrumNTSC TV sets will no longer be able to pick up broadcast signals
53 MPEG-7 Data + Multimedia Content Description Scheme Description Definition Language (XML-based)Still not ‘final’, but closeDoes not deal with data, but meta-data transmissionDescription Scheme + Content Description, e.g:Table of contentStill ImagesSummarieslinksetc.How does the Description data get generated? How is it used?
54 Mpeg-7 Examples <VideoText id="VideoText1" textType="Superimposed"><MediaTime><MediaTimePoint> T0:0:0:0 </MediaTimePoint><MediaDuration> PT6S </MediaDuration></MediaTime><Text xml:lang="en-us">CNN World News</Text></VideoText><TextProperty><FreeText xml:lang="en"> World Today </FreeText><SyncTime><MediaRelTimePoint>PT01N30F </MediaRelTimePoint><MediaDuration> PT2S </MediaDuration></SyncTime></TextProperty><Place>
55 Compression Schemes Quicktime (Apple), Video for Windows Open architecture allowing different codecsMotion JPEG – no interframe compressionCinepak is an asymmetric codec designed for 24-bit video in a 320 X 240 window for single-speed CD-ROM drives. Compression typically takes 300 times longer than decompression.Indeo asymmetric codec (Intel). Playback can take place on a Intel 486 processor without any hardware assistance. Less efficient than CinepakDVI Digital Video Interactive requires off-line supercomputer processing power for the compression.