教你辨别房屋出租骗子方法.ppt

1,Chapter7DigitalCameraExample,太原房产网,2,Outline,IntroductiontoasimpledigitalcameraDesignersperspectiveRequirementsspecificationDesignFourimplementations,3,PuttingitalltogetherGeneral-purposeprocessorSingle-purposeprocessorCustomStandardMemoryInterfacingKnowledgeappliedtodesigningasimpledigitalcameraGeneral-purposevs.single-purposeprocessorsPartitioningoffunctionalityamongdifferentprocessortypes,Introduction,4,Introductiontoasimpledigitalcamera,CapturesimagesStoresimagesindigitalformatNofilmMultipleimagesstoredincameraNumberdependsonamountofmemoryandbitsusedperimageDownloadsimagestoPCOnlyrecentlypossibleSystems-on-a-chipMultipleprocessorsandmemoriesononeICHigh-capacityflashmemoryVerysimpledescriptionusedforexampleManymorefeatureswithrealdigitalcameraVariablesizeimages,imagedeletion,digitalstretching,zoominginandout,etc.,5,Designersperspective,TwokeytasksProcessingimagesandstoringinmemoryWhenshutterpressed:ImagecapturedConvertedtodigitalformbycharge-coupleddevice(CCD)CompressedandarchivedininternalmemoryUploadingimagestoPCDigitalcameraattachedtoPCSpecialsoftwarecommandscameratotransmitarchivedimagesserially,6,Charge-coupleddevice(CCD),SpecialsensorthatcapturesanimageLight-sensitivesiliconsolid-statedevicecomposedofmanycells,7,Zero-biaserror,ManufacturingerrorscausecellstomeasureslightlyaboveorbelowactuallightintensityErrortypicallysameacrosscolumns,butdifferentacrossrowsSomeofleftmostcolumnsblockedbyblackpainttodetectzero-biaserrorReadingofotherthan0inblockedcellsiszero-biaserrorEachrowiscorrectedbysubtractingtheaverageerrorfoundinblockedcellsforthatrow,8,Compression,StoremoreimagesTransmitimagetoPCinlesstimeJPEG(JointPhotographicExpertsGroup)PopularstandardformatforrepresentingdigitalimagesinacompressedformProvidesforanumberofdifferentmodesofoperationModeusedinthischapterprovideshighcompressionratiosusingDCT(discretecosinetransform)Imagedatadividedintoblocksof8x8pixels3stepsperformedoneachblockDCTQuantizationHuffmanencoding,9,DCTstep,Transformsoriginal8x8blockintoacosine-frequencydomainUpper-leftcornervaluesrepresentmoreoftheessenceoftheimageLower-rightcornervaluesrepresentfinerdetailsCanreduceprecisionofthesevaluesandretainreasonableimagequalityFDCT(ForwardDCT)formulaC(h)=if(h=0)then1/sqrt(2)else1.0AuxiliaryfunctionusedinmainfunctionF(u,v)F(u,v)=xC(u)xC(v)x=0.7y=0.7Dxyxcos(2u+1)u/16)xcos(2y+1)v/16)Givesencodedpixelatrowu,columnvDxyisoriginalpixelvalueatrowx,columnyIDCT(InverseDCT)Reversesprocesstoobtainoriginalblock(notneededforthisdesign),10,Quantizationstep,AchievehighcompressionratiobyreducingimagequalityReducebitprecisionofencodeddataFewerbitsneededforencodingOnewayistodivideallvaluesbyafactorof2SimplerightshiftscandothisDequantizationwouldreverseprocessfordecompression,AfterbeingdecodedusingDCT,Afterquantization,Divideeachcellsvalueby8,11,Serialize8x8blockofpixelsValuesareconvertedintosinglelistusingzigzagpatternPerformHuffmanencodingMorefrequentlyoccurringpixelsassignedshortbinarycodeLongerbinarycodesleftforlessfrequentlyoccurringpixelsEachpixelinseriallistconvertedtoHuffmanencodedvaluesMuchshorterlist,thuscompression,Huffmanencodingstep,12,Huffmanencodingexample,PixelfrequenciesonleftPixelvalue1occurs15timesPixelvalue14occurs1timeBuildHuffmantreefrombottomupCreateoneleafnodeforeachpixelvalueandassignfrequencyasnodesvalueCreateaninternalnodebyjoininganytwonodeswhosesumisaminimalvalueThissumisinternalnodesvalueRepeatuntilcompletebinarytreeTraversetreefromroottoleaftoobtainbinarycodeforleafspixelvalueAppend0forlefttraversal,1forrighttraversalHuffmanencodingisreversibleNocodeisaprefixofanothercode,13,Archivestep,RecordstartingaddressandimagesizeCanuselinkedlistOnepossiblewaytoarchiveimagesIfmaxnumberofimagesarchivedisN:SetasidememoryforNaddressesandNimage-sizevariablesKeepacounterforlocationofnextavailableaddressInitializeaddressesandimage-sizevariablesto0SetglobalmemoryaddresstoNx4Assumingaddresses,image-sizevariablesoccupyNx4bytesFirstimagearchivedstartingataddressNx4GlobalmemoryaddressupdatedtoNx4+(compressedimagesize)MemoryrequirementbasedonN,imagesize,andaveragecompressionratio,14,UploadingtoPC,WhenconnectedtoPCanduploadcommandreceivedReadimagesfrommemoryTransmitseriallyusingUARTWhiletransmittingResetpointers,image-sizevariablesandglobalmemorypointeraccordingly,15,RequirementsSpecification,SystemsrequirementswhatsystemshoulddoNonfunctionalrequirementsConstraintsondesignmetrics(e.g.,“shoulduse0.001wattorless”)FunctionalrequirementsSystemsbehavior(e.g.,“outputXshouldbeinputYtimes2”)Initialspecificationmaybeverygeneralandcomefrommarketingdept.E.g.,shortdocumentdetailingmarketneedforalow-enddigitalcamerathat:capturesandstoresatleast50low-resimagesanduploadstoPC,costsaround$100withsinglemedium-sizeICcostinglessthat$25,haslongaspossiblebatterylife,hasexpectedsalesvolumeof200,000ifmarketentry6months,100,000ifbetween6and12months,insignificantsalesbeyond12months,16,Nonfunctionalrequirements,DesignmetricsofimportancebasedoninitialspecificationPerformance:timerequiredtoprocessimageSize:numberofelementarylogicgates(2-inputNANDgate)inICPower:measureofavg.electricalenergyconsumedwhileprocessingEnergy:batterylifetime(powerxtime)ConstrainedmetricsValuesmustbebelow(sometimesabove)certainthresholdOptimizationmetricsImprovedasmuchaspossibletoimproveproductMetriccanbebothconstrainedandoptimization,17,Nonfunctionalrequirements(cont.),PerformanceMustprocessimagefastenoughtobeuseful1secreasonableconstraintSlowerwouldbeannoyingFasternotnecessaryforlow-endofmarketTherefore,constrainedmetricSizeMustuseICthatfitsinreasonablysizedcameraConstrainedandoptimizationmetricConstraintmaybe200,000gates,butsmallerwouldbecheaperPowerMustoperatebelowcertaintemperature(coolingfannotpossible)Therefore,constrainedmetricEnergyReducingpowerortimereducesenergyOptimizedmetric:wantbatterytolastaslongaspossible,18,Informalfunctionalspecification,FlowchartbreaksfunctionalitydownintosimplerfunctionsEachfunctionsdetailscouldthenbedescribedinEnglishDoneearlierinchapterLowqualityimagehasresolutionof64x64Mappingfunctionstoaparticularprocessortypenotdoneatthisstage,19,Refinedfunctionalspecification,RefineinformalspecificationintoonethatcanactuallybeexecutedCanuseC/C+codetodescribeeachfunctionCalledsystem-levelmodel,prototype,orsimplymodelAlsoisfirstimplementationCanprovideinsightintooperationsofsystemProfilingcanfindcomputationallyintensivefunctionsCanobtainsampleoutputusedtoverifycorrectnessoffinalimplementation,Executablemodelofdigitalcamera,20,CCDmodule,SimulatesrealCCDCcdInitializeispassednameofimagefileCcdCapturereads“image”fromfileCcdPopPixeloutputspixelsoneatatime,charCcdPopPixel(void)charpixel;pixel=bufferrowIndexcolIndex;if(+colIndex=SZ_COL)colIndex=0;if(+rowIndex=SZ_ROW)colIndex=-1;rowIndex=-1;returnpixel;,#include#defineSZ_ROW64#defineSZ_COL(64+2)staticFILE*imageFileHandle;staticcharbufferSZ_ROWSZ_COL;staticunsignedrowIndex,colIndex;,voidCcdInitialize(constchar*imageFileName)imageFileHandle=fopen(imageFileName,r);rowIndex=-1;colIndex=-1;,voidCcdCapture(void)intpixel;rewind(imageFileHandle);for(rowIndex=0;rowIndexSZ_ROW;rowIndex+)for(colIndex=0;colIndexSZ_COL;colIndex+)if(fscanf(imageFileHandle,%i,21,CCDPP(CCDPreProcessing)module,Performszero-biasadjustmentCcdppCaptureusesCcdCaptureandCcdPopPixeltoobtainimagePerformszero-biasadjustmentaftereachrowreadin,#defineSZ_ROW64#defineSZ_COL64staticcharbufferSZ_ROWSZ_COL;staticunsignedrowIndex,colIndex;,voidCcdppInitialize()rowIndex=-1;colIndex=-1;,voidCcdppCapture(void)charbias;CcdCapture();for(rowIndex=0;rowIndexSZ_ROW;rowIndex+)for(colIndex=0;colIndexSZ_COL;colIndex+)bufferrowIndexcolIndex=CcdPopPixel();bias=(CcdPopPixel()+CcdPopPixel()/2;for(colIndex=0;colIndexSZ_COL;colIndex+)bufferrowIndexcolIndex-=bias;rowIndex=0;colIndex=0;,charCcdppPopPixel(void)charpixel;pixel=bufferrowIndexcolIndex;if(+colIndex=SZ_COL)colIndex=0;if(+rowIndex=SZ_ROW)colIndex=-1;rowIndex=-1;returnpixel;,22,UARTmodule,ActuallyahalfUARTOnlytransmits,doesnotreceiveUartInitializeispassednameoffiletooutputtoUartSendtransmits(writestooutputfile)bytesatatime,#includestaticFILE*outputFileHandle;voidUartInitialize(constchar*outputFileName)outputFileHandle=fopen(outputFileName,w);voidUartSend(chard)fprintf(outputFileHandle,%in,(int)d);,23,CODECmodule,ModelsFDCTencodingibufferholdsoriginal8x8blockobufferholdsencoded8x8blockCodecPushPixelcalled64timestofillibufferwithoriginalblockCodecDoFdctcalledoncetotransform8x8blockExplainedinnextslideCodecPopPixelcalled64timestoretrieveencodedblockfromobuffer,24,CODEC(cont.),ImplementingFDCTformulaC(h)=if(h=0)then1/sqrt(2)else1.0F(u,v)=xC(u)xC(v)x=0.7y=0.7Dxyxcos(2u+1)u/16)xcos(2y+1)v/16)Only64possibleinputstoCOS,sotablecanbeusedtosaveperformancetimeFloating-pointvaluesmultipliedby32,678androundedtonearestinteger32,678choseninordertostoreeachvaluein2bytesofmemoryFixed-pointrepresentationexplainedmorelaterFDCTunrollsinnerloopofsummation,implementsoutersummationastwoconsecutiveforloops,staticconstshortCOS_TABLE88=32768,32138,30273,27245,23170,18204,12539,6392,32768,27245,12539,-6392,-23170,-32138,-30273,-18204,32768,18204,-12539,-32138,-23170,6392,30273,27245,32768,6392,-30273,-18204,23170,27245,-12539,-32138,32768,-6392,-30273,18204,23170,-27245,-12539,32138,32768,-18204,-12539,32138,-23170,-6392,30273,-27245,32768,-27245,12539,6392,-23170,32138,-30273,18204,32768,-32138,30273,-27245,23170,-18204,12539,-6392;,staticintFDCT(intu,intv,shortimg88)doubles8,r=0;intx;for(x=0;x2?argv2:image.txt;/*initializethemodules*/UartInitialize(uartOutputFileName);CcdInitialize(imageFileName);CcdppInitialize();CodecInitialize();CntrlInitialize();/*simulatefunctionality*/CntrlCaptureImage();CntrlCompressImage();CntrlSendImage();,27,Design,DeterminesystemsarchitectureProcessorsAnycombinationofsingle-purpose(customorstandard)orgeneral-purposeprocessorsMemories,busesMapfunctionalitytothatarchitectureMultiplefunctionsononeprocessorOnefunctionononeormoreprocessorsImplementationAparticulararchitectureandmappingSolutionspaceissetofallimplementationsStartingpointLow-endgeneral-purposeprocessorconnectedtoflashmemoryAllfunctionalitymappedtosoftwarerunningonprocessorUsuallysatisfiespower,size,andtime-to-marketconstraintsIftimingconstraintnotsatisfiedthenlaterimplementationscould:usesingle-purposeprocessorsfortime-criticalfunctionsrewritefunctionalspecification,28,Implementation1:Microcontrolleralone,Low-endprocessorcouldbeIntel8051microcontrollerTotalICcostincludingNREabout$5Wellbelow200mWpowerTime-to-marketabout3monthsHowever,oneimagepersecondnotpossible12MHz,12cyclesperinstructionExecutesonemillioninstructionspersecondCcdppCapturehasnestedloopsresultingin4096(64x64)iterations100assemblyinstructionseachiteration409,000(4096x100)instructionsperimageHalfofbudgetforreadingimagealoneWouldbeoverbudgetafteraddingcompute-intensiveDCTandHuffmanencoding,29,Implementation2:MicrocontrollerandCCDPP,CCDPPfunctionimplementedoncustomsingle-purposeprocessorImprovesperformancelessmicrocontrollercyclesIncreasesNREcostandtime-to-marketEasytoimplementSimpledatapathFewstatesincontrollerSimpleUARTeasytoimplementassingle-purposeprocessoralsoEEPROMforprogrammemoryandRAMfordatamemoryaddedaswell,30,Microcontroller,SynthesizableversionofIntel8051availableWritteninVHDLCapturedatregistertransferlevel(RTL)FetchesinstructionfromROMDecodesusingInstructionDecoderALUexecutesarithmeticoperationsSourceanddestinationregistersresideinRAMSpecialdatamovementinstructionsusedtoloadandstoreexternallySpecialprogramgeneratesVHDLdescriptionofROMfromoutputofCcompiler/linker,31,UART,UARTinidlemodeuntilinvokedUARTinvokedwhen8051executesstoreinstructionwithUARTsenableregisterastargetaddressMemory-mappedcommunicationbetween8051andallsingle-purposeprocessorsLower8-bitsofmemoryaddressforRAMUpper8-bitsofmemoryaddressformemory-mappedI/OdevicesStartstatetransmits0indicatingstartofbytetransmissionthentransitionstoDatastateDatastatesends8bitsseriallythentransitionstoStopstateStopstatetransmits1indicatingtransmissiondonethentransitionsbacktoidlemode,invoked,I=8,I10millionintegeroperationsperimageProceduresincreasecodesizeFixed-pointarithmeticcanimproveonthis,39,Fixed-pointarithmetic,IntegerusedtorepresentarealnumberConstantnumberofintegersbitsrepresentsfractionalportionofrealnumberMorebits,moreaccuratetherepresentationRemainingbitsrepresentportionofrealnumberbeforedecimalpointTranslatingarealconstanttoafixed-pointrepresentationMultiplyrealvalueby2(#ofbitsusedforfractionalpart)RoundtonearestintegerE.g.,represent3.14as8-bitintegerwith4bitsforfraction24=163.14x16=50.2450=0011001016(24)possiblevaluesforfraction,eachrepresents0.0625(1/16)Last4bits(0010)=22x0.0625=0.1253(0011)+0.125=3.1253.14(morebitsforfractionwouldincreaseaccuracy),40,Fixed-pointarithmeticoperations,AdditionSimplyaddintegerrepresentationsE.g.,3.14+2.71=5.853.1450=001100102.7143=0010101150+43=93=010111015(0101)+13(1101)x0.0625=5.81255.85MultiplyMultiplyintegerrepresentationsShiftresultrightby#ofbitsinfractionalpartE.g.,3.14*2.71=8.509450*43=2150=1000011001104=100001108(1000)+6(0110)x0.0625=8.3758.5094Rangeofrealvaluesusedlimitedbybitwidthsofpossibleresultingvalues,41,Fixed-pointimplementationofCODEC,COS_TABLEgives8-bitfixed-pointrepresentationofcosinevalues6bitsusedforfractionalportionResultofmultiplicationsshiftedrightby6,voidCodecDoFdct(void)unsignedshortx,y;for(x=0;x6;return(short)(r*(16*C(u)6)*C(v)6)6)6);,voidCodecPushPixel(shortp)if(idx=64)idx=0;inBufferidx/8idx%8=p6;idx+;,42,Implementation3:MicrocontrollerandCCDPP/Fixed-PointDCT,Analysisofimplementation3Usesameanalysistechniquesasimplementation2Totalexecutiontimeforprocessingoneimage:1.5secondsPowerconsumption:0.033watt(sameas2)Energyconsumption:0.050joule(1.5sx0.033watt)Batterylife6xlonger!Totalchiparea:90,000gates8,000lessgates(lessmemoryneededforcode),43,Implementation4:MicrocontrollerandCCDPP/DCT,Perform