7.2. Design Overview

7.2.1. EncodingDataflowFigure

VENCModuleInputispendingEncodingimage, OutputisEncodingafterBitstream. VENCcontainshastwoModule, ReceiverandEncoder.

Receiver

• ReceiveimageInput

Encoder

• willreceivetoimageperform imageandVideo Encoding, Conversion Encoded Bitstream, The currently supported video standards are

  • JPEG

    Supported image formats are

    YUV422

    YUV420

    NV12 / NV21

  • MJPEG

    SupportimageFormatandJPEGsame

  • H.264

    Supported image formats are

    NV12

  • H.265

    Supported image formats are

    NV12

7.2.2. Video Encoding Channel

Video Encoding ChannelisVideo Encodingthisoperationsingle, internalmainincludingVENCRelatedFunction, ChannelRelatedSet. systemoncanhasmultipleVideo Encoding Channel, eachChanneloperation. eachChannelcreateafter, UsercanRequirementsSetChannelthisParameter, ifimageresolution, Encoding Bitrate, RCetc., RelatedParameterwillforVENCInitialize.

7.2.3. Rate Control

RCisEncoderMediumControlBitrateandVideo QualitymainModule, mainbyeachstandardinQPitemParameter, oneControlimagequality, When QPtime, EncodingtoDatawill, butVideo Qualitywill; When QPtime, EncodingtoDatawill, butVideo Qualitywill.

Video EncodingwillwithRCat the same timeoperation, If isimageEncoding (if JPEG), becauseonlyhassingleframeimage, notwillneed tothisModule.

Mode	JPEG	H.264	H.265
Fixed QP	Support	Support	Support
CBR	Support	Support	Support
VBR	Not supported	Support	Support
AVBR	Not supported	Support	Support

7.2.4. Fixed QP

instatisticstimein, imageinthehasMBUsesameaQPvalue.

7.2.5. CBR

CBR (Constant Bit Rate) fixedBitrate, dynamicControlQP, make Encoded Bitstream inSettimeregionin, in bitrate.

mainParameteras follows:

• u32StatTime Bitratestatisticstime

  • Unittimeisseconds (second), encoderwillinSettimeinstatisticsBitratewhileadjustimagequality, descriptorcombinedBitrate.

    When thisvaluetime, statisticsregion, imagequalitywillRelativelarger,

    eachoneframe Frame Compressioncompleteafter, forconnectundertoCompressionhaslargeraffect, qualitycomparenotstable.

    thisvaluetime, statisticsregion, eachoneframeFrameCompressioncompleteafteraffectlevelsmaller, imagesmaller, qualitycomparestable.

7.2.6. VBR

VBR(Variable Bit Rate) canBitrate, BitrateinSetstatisticstimein, dynamicadjustbodyBitrate, canmakeimagequalityRelativestable.

• u32MaxBitRate MaximumBitrate

  • Set the maximum usable bitrate during the statistics period

• u32MinQp

  • SetMinimumcanUse MB QP, limitimageoptimalquality, notwillUseheightBitrate

7.2.7. AVBR

AVBR(Adaptive Variable Bit Rate)autoshouldcanBitrate. scenemotionleveldynamicadjuststatisticstimeDestinationBitrate, Rate Controlinternalscenemotionleveldetermine. scenemotionlevellarger, DestinationBitrateheight, whileWhen scenetostatictime, willautomaticlowDestinationBitrate.

• u32MaxBitRate MaximumBitrate

  • Set the maximum usable bitrate during the statistics period

• u32MinStillPercent

  • scenestaticStatustime, DestinationBitratewithMaximumBitrateof

  • MinBitrate = MaxBitrate*ChangePos*MinStillPercnet

• According toscenemotionlevel, DestinationBitrateinMinBitratewithMaxBitratetuning

• U32MaxStillQp

  • scenecompletelystatictime, maxQptoMaxStillQp. withstaticsceneimagequality.

7.2.8. GOP Structure

H.264 and H.265 For GOP StructureSupportstatusas follows.

GOPMode	H.264	H.265
NormalP	Support	Support
SmartP	Support	Support

• NormalPGOP Structureas follows

  • IDR Frameappearis u32Gop

• SmartPGOP Structureas follows

  • VIFrameappearisu32Gop, thisFrameonlytobeforeReferenceofIDRFrame

  • IDRFrameappearisu32BgInterval, this IDR FrameisReferenceFrame

7.2.9. Advanced Frame Skipping

H.264 and H.265Support1times, 2times, and4frame-skipping reference mode. defaultis1times(notFrame).

• 2frame-skipping reference modeas follows

7.2.10. ROI

ROI (Region Of Interest) Encoding: RegionEncoding.

• UsercanthroughConfiguration ROI Region, tuningthisRegionImage Qp, implementImageinRegion.

• H.264 and H.265Support 8 item ROI Set, repeatRegionaccording to 0～7 ROIIndexnumbersecondaryprovideheightfirstlevel

• ROI RegioncanConfigurationAbsoluteQpandRelativeQptwoMode.

  • AbsoluteQp Mode: ROI RegionQpisUserSet Qp value.

  • RelativeQpMode: ROIRegionQpisRate ControlofQponUserSetQpvalue.

• Precautions

  • When Rate ControlModenotisFixed QPModetime, ROIRegioncanConfiguration.

  • H.264When ROIcantime, Macroblock-LevelRate Controleffective.

  • AbsoluteQpModebecauseRate ControltuningmacroblockQP, actualEncodingQPwithSetofQPcancanwillhas.

7.2.11. EncodingBitstreamFrameConfigurationMode

CompressionafterEncodingBitstream, UseCVI_VENC_GetStreamGetEncoded Bitstream, RelatedInformationas follows:

• u32PackCount

  • thisframeFramecontainshasmultipleitemNAL packet,

    For examplebeforeCompressionFormatisH.264, firstframe isI frame, thisvaluewillis 3 (containsSPS, PPS, 1 Slice),

    secondframeFrameis 1(contains1 Slice).

• pstPack

  • According tou32PackCountQuantity, willcontainshaspstPack[0] ~ pstPack[u32PackCount - 1] data.

    iffirstframeI Frame, willhaspstPack[0], pstPack[1], pstPack[2]

• underFigureisfirstframe I FrameBitstreamdata

7.2.12. multipleEncodingdeviceandEncoding

H.264 and H.265 Supportmultiple channelsEncoding, beforedefaultmultipleis 8 andEncoding, withunderisPrecautions

• Encodingbodyeffectivecanneed tolower thanHardwaresetlimit, exceedswillNonemethodreachSetframerate

• theneed toFrame Bufferwillwithnumberincreasecurrentlyincrease, DRAMUseofincrease

7.2.13. Encoded Frame Buffer Calculation

EncodingFramecache (ReferenceFrameandFrame) allocateSupporttwoMethod: PrivateVB poolMethodand UserVB poolMethod. Encoding PrivateVB poolMethod: CreateEncoding channeltimeby VENC CreatehasVBpoolisthisChannelReferenceFrameandFrameBuffer. EncodingUserVBpoolMethod (only H.264/H.265 EncodingSupport): CreateEncoding channeltimenotallocateReferenceFrameandFrameBuffer, whileisbyUserCallInterfaceCVI_VB_CreatePool

Create a VideocacheVBpool, thenthroughCallInterfaceCVI_VENC_AttachVbPoolitemEncoding channelBindtofixedVideocacheVBpoolin. twoMethodcanthroughCall CVI_VENC_SetModParamInterfaceSetshouldModuleParametertoselect. ModuleParameterSetis VB_SOURCE_PRIVATEmeansUseEncodingPrivateVBpoolMethod; Setis VB_SOURCE_USERmeansUseEncodingUserVBpoolMethod.

UserVBModeunder, EncodingFrameMemoryMaximumvalueReferenceas follows

	H.264	H.265
FrameSize	(align(width,32)) x (align(height,32)) x 1.5 x 2	align((width x height x 1.5), 4096) x 2