ErrataforUSBVideoPayloadH2641.0Erratafor“USBVideoPayloadH2641.0”asofAugust9,2011.Checkthehttp://www.usb.orgwebsiteforthelatesterrata.1.ErratawLayerIDSection3.3.2.1ofSpecification“USBVideoPayloadH2641.0”Section2.21ofFAQ““USBVideoPayloadH264FAQ1.0”Background:ThewLayerIDstructureparametersbitsarenotconsistentwiththeH.264specification.Change:wLayerIDReserved(3bits)StreamID(3bits)QualityID(3bits)DependencyID(4bits)TemporalID(3bits)15131210976320Table3:wLayerIDStructureChangeto:wLayerIDforSVCStreamsReserved(3bits)StreamID(3bits)TemporalID(3bits)QualityID(4bits)DependencyID(3bits)15131210976320wLayerIDforMVCStreamsReserved(3bits)StreamID(3bits)TemporalID(3bits)ViewID(7bits)151312109760Table3:wLayerIDStructureErrataforUSBVideoPayloadH2641.0StreamID:TheStreamIDprovidesspecificationofaspecificH.264streaminthecaseofasimulcastsequence.TheStreamIDhas3bits(bits12-10inwLayerID)tosupport7streams(0-6).Avalueof7shallbeusedtosimultaneouslyrefertoallstreams.InthecaseofasingleH.264stream,stream_idisalways0.Non-zeroStreamIDonlyappearsincasesofsimulcastoftwoormoreH.264streams.TemporalID:TheTemporalIDprovidesspecificationofaspecificTemporalLayerinamulti-layerSVC/MVCstream.TheTemporalIDhas3bits(bits9-7inwLayerID)tosupport7temporallayers(0enhancements–6enhancementslayers).Avalueof7shallbeusedtosimultaneouslyrefertoalltemporallayers.Inthecaseofasingle-layerH.264stream,TemporalIDshallalwaysbe0.InthecaseofaSVCstreamnotusingtemporalscalability,TemporalIDshallalwaysbe0.Anon-zeroTemporalIDshallonlyappearinSVCstreamsusingtemporalscalabilitywhere1indicatesthefirsttemporalenhancementlayer,uptothemaximumtemporalEnhancementlayerbTemporalScaleModesetintheUVCX_TEMPORAL_SCALE_MODEcontrol.QualityID:TheQualityIDprovidesspecificationofaspecificQualitylayerinamulti-layerSVCstream.TheQualityIDhas4bits(bits6-3inwLayerID)tosupport15Qualitylayers(0enhancements–14enhancementslayers).Avalueof15shallbeusedtosimultaneouslyrefertoallqualitylayers.Inthecaseofasingle-layerH.264stream,QualityIDshallalwaysbe0.InthecaseofaSVCstreamnotusingMGSmodeSNRscalability,QualityIDshallalwaysbe0.Anon-zeroQualityIDshallonlyappearinSVCstreamsusingMGSmodeSNRscalabilitywhere1indicatesthefirstqualityenhancementlayer,uptothemaximumqualityEnhancementlayer.TheMSGmodeofSNRscalabilitypartitionstransformcoefficientsintoseparateQualitylayers.DependencyID:TheDependencyIDprovidesspecificationofaspecificDependencyLayerinamulti-layerSVCstream.TheDependencyIDhas3bits(bits2-0inwLayerID)tosupport7dependencylayers(0enhancements–6enhancementslayers).Avalueof7shallbeusedtosimultaneouslyrefertoallDependencylayers.Inthecaseofasingle-layerH.264stream,DependencyIDshallalwaysbe0.InthecaseofaSVCstreamnotusingeitherCGSmodeSNRscalabilityorSpatialscalabilitymode,DependencyIDshallalwaysbe0.Anon-zeroDependencyIDshallonlyappearinSVCstreamsusingeitherCGSmodeSNRscalabilityorSpatialscalabilitywhere1indicatesthefirstSNRorspatialenhancementlayer,uptothemaximumSNRorspatialEnhancementlayerdefinedasthesumofbSpatialScaleModeandthenumberofCGSmodeSNRscalableenhancementlayersidentifiedintable8.ViewID:TheViewIDprovidesspecificationofaspecificviewinaMVCstream.TheViewIDhas7bits(bits6-0inwLayerID)tosupport62views(0views–62views).Avalueof63shallbeusedtosimultaneouslyreferallviews.Values64to127arereserved.ErrataforUSBVideoPayloadH2641.0Reserved:TheReservedfieldhas3bits(bits15-13inwLayerID)andshallalwaysbe0.2.ErrataAppendixC“USBVideoPayloadH2641.0”Section6.1.1CorrelatingbetweenDeviceandPCclocksBackground:Theclarificationontheclockexposed.Changedto:Sincethecapturetimeofthevideoframe(PTS)isindicatedbythedeviceusingtheSTC,andA/VsyncwillrelyonPCclockvalue,weneedtocorrelatethetwoclocks.OnWindows,thePCclockexposedviatheQueryPerformanceCounter(QPC).Thecorrelation‘constant’betweenPTSandQPCcanbecalculatedasthemostrecentTotalVideoDelay.ClockCorrelationConstant(CCC)=TotalVideoDelayEquation4Section6.1.2VideoTimeStampingBackground:Equation5correction.Changedto:Thetimestampappliedbythevideodrivertothecurrentvideoframeiscalculatedasthetimestampforthecurrentframe–CCC.Timestampforcurrentframe=QPC-CCCEquation5ThetimestampcalculatedaboveisappliedbythehostdrivertoallNALUnitsbelongtothesamepicture.ThecameraindicatesanewpicturebytogglingtheFIDbetween0and1ontheUVCpayloadheader.
