Understanding VC-1
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There is a WMV9/VC-1 reference decoder available on the internet which answers to the filename vc1_reference_decoder_release6.zip. This section of the MultimediaWiki is an effort to create an open VC-1 specification based on that reference implementation.
These functions are necessary for processing VC-1 data using the reference decoder:
// set up pointers to bitstream (extradata) in internal state structure vc1DECBIT_InitialiseBitstream // analyze how much memory the client app needs to allocate vc1DEC_DecoderRequirements // init decoder vc1DEC_DecoderInitialise // process the extradata setup bitstream vc1DEC_DecodeSequence // decode a frame vc1DEC_DecodeFrame
These are the call trees for the above functions
vc1DECBIT_InitialiseBitstream +- vc1DECBIT_ReadBytes
vc1DEC_DecoderRequirements +- vc1DECBIT_GetBits +- vc1TOOLS_InitReferencePicture +- vc1TOOLS_InitImagePosition
vc1DEC_DecoderInitialise +- vc1DEC_SetMaxSize +- vc1TOOLS_InitReferencePicture
vc1DEC_DecodeSequence +- vc1DECSEQ_UnpackSequenceLayer +- vc1DECBIT_GetBits
vc1DEC_DecodeFrame
+- vc1DECPIC_UnpackPictureLayer
+- vc1DECPIC_ReadPictureLayer
+- vc1DECBIT_GetBits
+- vc1DECPIC_SetDimensionsInMB
+- vc1DECPIC_UnpackPictureLayerAdvanced
+- vc1DECBIT_GetBits
+- vc1DECBIT_GetVLC
+- vc1DECPIC_UnpackPanScanParams
+- vc1DECBIT_GetBits
+- vc1DECPIC_UnpackPictureLayerSimpleMain
+- vc1DECBIT_BitCountGet
+- vc1DECBIT_GetBits
+- vc1DECBIT_GetVLC
+- vc1DECPIC_UnpackQuantizationParams
+- vc1DECBIT_GetBits
+- vc1IQUANT_GetQuantizer
+- vc1DECPIC_SetDimensionsInMB
+- vc1DECBITPL_ReadBitplane
+- vc1DECBIT_GetBits
+- vc1DECBIT_GetVLC
+- vc1DECBITPL_DecodeNorm2Bits
+- vc1DECBIT_GetBits
+- vc1DECBIT_GetVLC
+- vc1DECBITPL_DecodeNorm6Bits
+- vc1DECBIT_GetBits
+- vc1DECBIT_GetVLC
+- vc1DECBITPL_DecodeRowskipBits
+- vc1DECBIT_GetBits
+- vc1DECBITPL_DecodeColskipBits
+- vc1DECBIT_GetBits
+- vc1DECBITPL_DecodeRawBits
+- vc1DECPIC_UnpackVOPDQUANTParams
+- vc1DECBIT_GetBits
+- vc1DECPIC_UnpackFieldPictureLayer
+- vc1DECPIC_ReadAdvancedPictureLayer
+- vc1DECPIC_UnpackFieldPictureLayerIAdvanced
+- vc1DECPIC_UnpackQuantizationParams
+- vc1DECBIT_GetBits
+- vc1DECBITPL_ReadBitplane
+- vc1DECBIT_GetVLC
+- vc1DECPIC_UnpackVOPDQUANTParams
+- vc1DECPIC_UnpackFieldPictureLayerPBAdvanced
+- vc1DECPIC_UnpackQuantizationParams
+- vc1DECBIT_GetBits
+- vc1DECBIT_GetVLC
+- vc1DECPIC_UnpackInterlaceMVModeParams
+- vc1DECBITPL_ReadBitplane
+- vc1DECPIC_DisplayPicture
+- vc1DECPIC_DisplayField
+- vc1DECPIC_InitialiseAppPicture
+- vc1TOOLS_ResolutionUpsample
+- vc1TOOLS_InitReferencePicture
+- vc1TOOLS_NewReference
+- vc1TOOLS_CopyReference
+- vc1TOOLS_ICPadReferencePicture
+- vc1TOOLS_RangeReduceReference
+- vc1TOOLS_RangeReduce16
+- vc1TOOLS_RangeExpand
+- vc1TOOLS_IntensityCompensate
+- vc1TOOLS_ICComponent
+- vc1TOOLS_PadReferencePicture
+- vc1TOOLS_PadComponent
+- vc1SCALEMV_InitScaleMV
+- vc1DECSLICE_DecodeSlice
+- vc1DECBIT_GetBits
+- vc1DECPIC_UnpackSyncmarker
+- vc1DECBIT_AlignBit
+- vc1DECBIT_ReadBytes
+- vc1DECBIT_GetBits
+- vc1DECMB_UnpackMacroblockLayer
+- vc1IQUANT_ChooseQuantizer
+- vc1DECMB_UnpackMacroblockI
+- vc1DECBITPL_ReadBitplaneBit
+- vc1DECBIT_GetBits
+- vc1DECBIT_GetVLC
+- vc1PREDCBP_ApplyCBPCYPred
+- vc1DECBIT_GetBits
+- vc1DECMB_UnpackMBQuantParams
+- vc1DECBIT_GetBits
+- vc1DECMB_UnpackMacroblockProgP
+- vc1DECBITPL_ReadBitplaneBit
+- vc1DECMB_UnpackMacroblockProgPSkipped
+- vc1DECBIT_LookBits
+- vc1DECBIT_ReadBits
+- vc1PREDMV_PredictProgressiveMV
+- vc1PRED_pTopBlk
+- vc1PRED_pLeftBlk
+- vc1PRED_pB1MVBlk
+- vc1PRED_pB4MVBlk
+- vc1TOOLS_Median3
+- vc1CROPMV_BPredPullBack
+- vc1DECBIT_GetBits
+- vc1DECMV_ApplyMVPrediction
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMB_UnpackMacroblockProgP1MV
+- vc1DECMV_UnpackMVData
+- vc1DECBIT_LookBits
+- vc1PREDMV_PredictProgressiveMV
+- vc1DECBIT_GetBits
+- vc1DECMV_ApplyMVPrediction
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMB_UnpackMBQuantParams
+- vc1DECBIT_GetVLC
+- vc1DECMB_DecodeTransformInfo
+- vc1DECMB_UnpackTTMB
+- vc1DECBIT_GetVLC
+- vc1DECMB_UnpackMacroblockProgP4MV
+- vc1DECBIT_GetVLC
+- vc1DECMV_UnpackMVData
+- vc1DECBIT_LookBits
+- vc1PREDMV_PredictProgressiveMV
+- vc1DECBIT_GetBits
+- vc1DECMV_ApplyMVPrediction
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMB_UnpackMBQuantParams
+- vc1PREDDCAC_ACPREDPresent
+- vc1DECMB_DecodeTransformInfo
+- vc1DECMB_UnpackMacroblockFieldP
+- vc1DECBIT_GetVLC
+- vc1DECMV_UnpackMVDataInterlace
+- vc1DECBIT_GetVLC
+- vc1DECBIT_GetBits
+- vc1DECBIT_LookBits
+- vc1PREDMV_PredictInterlacedFieldMV
+- vc1SCALEMV_ScaleMV
+- vc1TOOLS_Median3
+- vc1DECBIT_GetBits
+- vc1DECMV_ApplyMVPrediction
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMB_UnpackMBQuantParams
+- vc1DECMB_DecodeTransformInfo
+- vc1DECMB_UnpackMacroblockFrameP
+- vc1DECBITPL_ReadBitplaneBit
+- vc1PREDMV_PredictInterlacedFrameMV
+- vc1PREDMV_FrameMBPred
+- vc1TOOLS_Median3
+- vc1DECMV_ApplyMVPrediction
+- vc1DECBIT_GetVLC
+- vc1DECBIT_GetBits
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMB_UnpackMBQuantParams
+- vc1DECMV_UnpackMVDataInterlace
+- vc1DECMB_UnpackMacroblockProgB
+- vc1DECBITPL_ReadBitplaneBit
+- vc1DECMV_UnpackMVData
+- vc1DECBIT_GetVLC
+- vc1DECMB_UnpackMBQuantParams
+- vc1DECBIT_GetBits
+- vc1PREDMV_PredictProgressiveMV
+- vc1DECMV_ApplyMVPrediction
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMB_DecodeTransformInfo
+- vc1DECMB_UnpackMacroblockFieldB
+- vc1DECBIT_GetVLC
+- vc1DECBITPL_ReadBitplaneBit
+- vc1DECBITPL_SkipBitplaneBit
+- vc1DECBIT_GetBits
+- vc1DECMV_UnpackMVDataInterlace
+- vc1PREDMV_PredictInterlacedFieldMV
+- vc1DECMV_ApplyMVPrediction
+- vc1DECMB_UnpackMBQuantParams
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMB_DecodeTransformInfo
+- vc1DECMB_UnpackMacroblockFrameB
+- vc1DECBITPL_ReadBitplaneBit
+- vc1DECBIT_GetVLC
+- vc1DECBITPL_SkipBitplaneBit
+- vc1DECBIT_GetBits
+- vc1DECMB_UnpackMBQuantParams
+- vc1DERIVEMV_DecideChromaBlockType
+- vc1DECMV_UnpackMVDataInterlace
+- vc1PREDMV_PredictInterlacedFrameMV
+- vc1DECMV_ApplyMVPrediction
+- vc1DECMB_AssignCodedBlockPattern
+- vc1DECBLK_DecodeBlockLayer
+- vc1DECBLK_UnpackIntraBlock
+- vc1PREDDCAC_DCDefault
+- vc1PREDDCAC_DCStepSize
+- vc1PREDDCAC_PredictDCAC
+- vc1PREDDCAC_GetQuant
+- vc1PREDDCAC_ScaleDC
+- vc1PREDDCAC_DCStepSize
+- vc1DECBLK_UnpackDCDifferential
+- vc1DECBIT_GetVLC
+- vc1DECBIT_GetBits
+- vc1DEC3DH_DecodeACRunLevel
+- vc1DEC3DH_ChooseACCodingSet
+- vc1DEC3DH_ChooseEscapeMode3Table
+- vc1DEC3DH_UnpackTransformACCoef
+- vc1DECBIT_GetVLC
+- vc1DECBIT_GetBits
+- vc1DECZZ_DeZigZagBlock
+- vc1DECZZ_DeZigZag
+- vc1DECBLK_ApplyACPrediction
+- vc1PREDDCAC_CopyDCAC
+- vc1DECBLK_UnpackInterBlock
+- vc1DECBLK_UnpackSubBlockPattern
+- vc1DECBIT_GetVLC
+- vc1DECBLK_UnpackTTBLK
+- vc1DECBIT_GetVLC
+- vc1DEC3DH_DecodeACRunLevel
+- vc1DECZZ_DeZigZagBlock
+- vc1INTERP_PredictMB
+- vc1DERIVEMV_StoreMotionVectors
+- vc1DERIVEMV_DeriveMV
+- vc1DERIVEMV_DirectMV
+- vc1DERIVEMV_DeriveProgMV
+- vc1TOOLS_Median3
+- vc1TOOLS_Median4
+- vc1CROPMV_ChromaPullBack
+- vc1DERIVEMV_DeriveIntFieldMV
+- vc1TOOLS_Median4
+- vc1TOOLS_Median3
+- vc1DERIVEMV_DeriveIntFrameDirectMV
+- vc1CROPMV_PPredPullBack
+- vc1DERIVEMV_FillInInterlaceFieldMV
+- vc1PREDMV_PredictInterlacedFieldMV
+- vc1SCALEMV_ScaleMV
+- vc1TOOLS_Median3
+- vc1INTERP_InterpolateBlock
+- vc1CROPMV_LumaPullBack
+- vc1DERIVEMV_DeriveChromaMV
+- vc1DERIVEMV_DeriveProgMV
+- vc1CROPMV_LumaPullBack
+- vc1DERIVEMV_DeriveSecondStageChromaMV
+- vc1CROPMV_ChromaPullBack
+- vc1DERIVEMV_DeriveIntFieldMV
+- vc1TOOLS_Median4
+- vc1CROPMV_ChromaPullBack
+- vc1INTERP_InterpPatchQuarterPelBilinear
+- vc1INTERP_InterpPatchHalfPelBilinear
+- vc1INTERP_InterpPatchQuarterPelBilinear
+- vc1INTERP_InterpPatchQuarterPelBicubic
+- vc1INTERP_CopyPatch
+- vc1INTERP_InterpPatchQuarterPelBicubicVert
+- vc1INTERP_InterpPatchQuarterPelBicubicHoriz
+- vc1INTERP_InterpPatchQuarterPelBicubicDiag
+- vc1INTERP_InterpPatchHalfPelBicubic
+- vc1INTERP_InterpPatchQuarterPelBicubic
+- vc1INTERP_AverageBlocks
+- vc1RECON_ReconstructMB
+- vc1IQUANT_InverseACQuantize
+- vc1IQUANT_InverseDCQuantize
+- vc1PREDDCAC_DCStepSize
+- vc1ITRANS_InverseTransformBlock
+- vc1ITRANS_InverseTransform_AnnexA1
+- vc1RECON_ApplyPredictionAndCopyMB
+- vc1INTERP_InterlaceDiffMB
+- vc1INTERP_InterlacePredMB
+- vc1SMOOTH_OverlapSmoothMB
+- vc1PRED_pLeftMB
+- vc1TOOLS_GetPictureDestination
+- vc1SMOOTH_OverlapSmoothVertBlk
+- vc1SMOOTH_OverlapSmoothHorizMB
+- vc1TOOLS_GetPictureDestination
+- vc1SMOOTH_OverlapSmoothHorizBlk
+- vc1TOOLS_GetPictureDestination
+- vc1SMOOTH_OverlapSmoothHorizMB
+- vc1DEBLOCK_DeblockSlice
+- vc1DEBLOCK_HorizDeblockMB
+- vc1TOOLS_GetPictureDestination
+- vc1DEBLOCK_HorizDeblockBlk
+- vc1DEBLOCK_VertDeblockMB
+- vc1TOOLS_GetPictureDestination
+- vc1DEBLOCK_VertDeblockBlk
+- vc1TOOLS_CopyReference
+- vc1DECPIC_DisplayPicture
vc1DECBIT_GetVLC
The GetVLC function returns the value represented by the next variable length code (i.e., Huffman) code in the bitstream. The reference decoder performes this operation in an exceptionally slow manner but it is also not held to any specific performance standards. Thus, a new VC-1 implementation should maintain VLC tables and decoder values from then however it sees fit to do so.
vc1TOOLS_Median3
The Median3 function takes 3 numbers as input and returns the middle value of the 3.
vc1TOOLS_Median4
The Median4 function takes 4 numbers as input and returns the average between the middle 2 values of the set, weighted down. For 4 inputs, (a, b, c, d), find the minimum and maximum values of the set (min, max) and the media 4 value is computed as:
(a + b + c + d - min - max) / 2