Merged in nal-extension-types (pull request #216)

codec/h264/h264dec: NAL unit extension types and clean up

codec/h264/h264dec/frame.go

@@ -19,6 +19,8 @@ const (
 	naluTypePrefixNALU
 	naluTypeSubsetSPS
 	naluTypeDepthParamSet
+	naluTypeSliceLayerExtRBSP  = 20
+	naluTypeSliceLayerExtRBSP2 = 21
 )
 
 var (

codec/h264/h264dec/nalunit.go

@@ -1,161 +1,291 @@
+/*
+DESCRIPTION
+  nalunit.go provides structures for a NAL unit as well as it's extensions.
+
+AUTHORS
+  Saxon Nelson-Milton <saxon@ausocean.org>, The Australian Ocean Laboratory (AusOcean)
+  mrmod <mcmoranbjr@gmail.com>
+*/
+
 package h264dec
 
 import (
-	"bitbucket.org/ausocean/av/codec/h264/h264dec/bits"
+	"fmt"
+	"io"
+
 	"github.com/pkg/errors"
+
+	"bitbucket.org/ausocean/av/codec/h264/h264dec/bits"
 )
 
-type NalUnit struct {
+// MVCExtension describes a NAL unit header multiview video coding extension, as
-	NumBytes                     int
+// defined in section H.7.3.1.1 of the specifications.
-	ForbiddenZeroBit             int
+// Semantics of fields are specified in section H.7.4.1.1.
-	RefIdc                       int
+type MVCExtension struct {
-	Type                         int
+	// non_idr_flag, if true indicates that access unit is not IDR.
-	SvcExtensionFlag             int
+	NonIdrFlag bool
-	Avc3dExtensionFlag           int
+
-	IdrFlag                      int
+	// priority_id, indicates priority of NAL unit. A lower value => higher priority.
-	PriorityId                   int
+	PriorityID uint8
-	NoInterLayerPredFlag         int
+
-	DependencyId                 int
+	// view_id, specifies a view identifier for the unit. Units with identical
-	QualityId                    int
+	// view_id are in the same view.
-	TemporalId                   int
+	ViewID uint32
-	UseRefBasePicFlag            int
+
-	DiscardableFlag              int
+	// temporal_id, temporal identifier for the unit.
-	OutputFlag                   int
+	TemporalID uint8
-	ReservedThree2Bits           int
+
-	HeaderBytes                  int
+	// anchor_pic_flag, if true access unit is an anchor access unit.
-	NonIdrFlag                   int
+	AnchorPicFlag bool
-	ViewId                       int
+
-	AnchorPicFlag                int
+	// inter_view_flag, if false current view component not used for inter-view
-	InterViewFlag                int
+	// prediction elsewhere in access unit.
-	ReservedOneBit               int
+	InterViewFlag bool
-	ViewIdx                      int
+
-	DepthFlag                    int
+	// reserved_one_bit, always 1 (ignored by decoders)
+	ReservedOneBit uint8
+}
+
+// NewMVCExtension parses a NAL unit header multiview video coding extension
+// from br following the syntax structure specified in section H.7.3.1.1, and
+// returns as a new MVCExtension.
+func NewMVCExtension(br *bits.BitReader) (*MVCExtension, error) {
+	e := &MVCExtension{}
+	r := newFieldReader(br)
+
+	e.NonIdrFlag = r.readBits(1) == 1
+	e.PriorityID = uint8(r.readBits(6))
+	e.ViewID = uint32(r.readBits(10))
+	e.TemporalID = uint8(r.readBits(3))
+	e.AnchorPicFlag = r.readBits(1) == 1
+	e.InterViewFlag = r.readBits(1) == 1
+	e.ReservedOneBit = uint8(r.readBits(1))
+
+	if r.err() != nil {
+		return nil, fmt.Errorf("error from fieldReader: %v", r.err())
+	}
+	return e, nil
+}
+
+// ThreeDAVCExtension describes a NAL unit header 3D advanced video coding
+// extension, as defined in section J.7.3.1.1 of the specifications.
+// For field semantics see section J.7.4.1.1.
+type ThreeDAVCExtension struct {
+	// view_idx, specifies the order index for the NAL i.e. view_id = view_id[view_idx].
+	ViewIdx uint8
+
+	// dpeth_flag, if true indicates NAL part of a depth view component, otherwise
+	// a texture view component.
+	DepthFlag bool
+
+	// non_idr_flag, if true indicates that access unit is not IDR.
+	NonIdrFlag bool
+
+	// temporal_id, temporal identifier for the unit.
+	TemporalID uint8
+
+	// anchor_pic_flag, if true access unit is an anchor access unit.
+	AnchorPicFlag bool
+
+	// inter_view_flag, if false current view component not used for inter-view
+	// prediction elsewhere in access unit.
+	InterViewFlag bool
+}
+
+// NewThreeDAVCExtension parses a NAL unit header 3D advanced video coding
+// extension from br following the syntax structure specified in section
+// J.7.3.1.1, and returns as a new ThreeDAVCExtension.
+func NewThreeDAVCExtension(br *bits.BitReader) (*ThreeDAVCExtension, error) {
+	e := &ThreeDAVCExtension{}
+	r := newFieldReader(br)
+
+	e.ViewIdx = uint8(r.readBits(8))
+	e.DepthFlag = r.readBits(1) == 1
+	e.NonIdrFlag = r.readBits(1) == 1
+	e.TemporalID = uint8(r.readBits(3))
+	e.AnchorPicFlag = r.readBits(1) == 1
+	e.InterViewFlag = r.readBits(1) == 1
+
+	if r.err() != nil {
+		return nil, fmt.Errorf("error from fieldReader: %v", r.err())
+	}
+
+	return e, nil
+}
+
+// SVCExtension describes a NAL unit header scalable video coding extension, as
+// defined in section G.7.3.1.1 of the specifications.
+// For field semantics see section G.7.4.1.1.
+type SVCExtension struct {
+	// idr_flag, if true the current coded picture is an IDR picture when
+	// dependency_id == max(dependency_id) in the coded picture.
+	IdrFlag bool
+
+	// priority_id, specifies priority identifier for unit.
+	PriorityID uint8
+
+	// no_inter_layer_pred_flag, if true inter-layer prediction can't be used for
+	// decoding slice.
+	NoInterLayerPredFlag bool
+
+	// dependency_id, specifies a dependency identifier for the NAL.
+	DependencyID uint8
+
+	// quality_id, specifies a quality identifier for the NAL.
+	QualityID uint8
+
+	// temporal_id, specifiesa temporal identifier for the NAL.
+	TemporalID uint8
+
+	// use_ref_base_pic_flag, if true indicates reference base pictures and
+	// decoded pictures are used as references for inter prediction.
+	UseRefBasePicFlag bool
+
+	// discardable_flag, if true, indicates current NAL is not used for decoding
+	// dependency representations that are part of the current coded picture or
+	// any subsequent coded picture in decoding order and have a greater
+	// dependency_id value than current NAL.
+	DiscardableFlag bool
+
+	// output_flag, affects the decoded picture output and removal processes as
+	// specified in Annex C.
+	OutputFlag bool
+
+	// reserved_three_2bits, equal to 3. Decoders ignore.
+	ReservedThree2Bits uint8
+}
+
+// NewSVCExtension parses a NAL unit header scalable video coding extension from
+// br following the syntax structure specified in section G.7.3.1.1, and returns
+// as a new SVCExtension.
+func NewSVCExtension(br *bits.BitReader) (*SVCExtension, error) {
+	e := &SVCExtension{}
+	r := newFieldReader(br)
+
+	e.IdrFlag = r.readBits(1) == 1
+	e.PriorityID = uint8(r.readBits(6))
+	e.NoInterLayerPredFlag = r.readBits(1) == 1
+	e.DependencyID = uint8(r.readBits(3))
+	e.QualityID = uint8(r.readBits(4))
+	e.TemporalID = uint8(r.readBits(3))
+	e.UseRefBasePicFlag = r.readBits(1) == 1
+	e.DiscardableFlag = r.readBits(1) == 1
+	e.OutputFlag = r.readBits(1) == 1
+	e.ReservedThree2Bits = uint8(r.readBits(2))
+
+	if r.err() != nil {
+		return nil, fmt.Errorf("error from fieldReader: %v", r.err())
+	}
+	return e, nil
+}
+
+// NALUnit describes a network abstraction layer unit, as defined in section
+// 7.3.1 of the specifications.
+// Field semantics are defined in section 7.4.1.
+type NALUnit struct {
+	// forbidden_zero_bit, always 0.
+	ForbiddenZeroBit uint8
+
+	// nal_ref_idc, if not 0 indicates content of NAL contains a sequence parameter
+	// set, a sequence parameter set extension, a subset sequence parameter set,
+	// a picture parameter set, a slice of a reference picture, a slice data
+	// partition of a reference picture, or a prefix NAL preceding a slice of
+	// a reference picture.
+	RefIdc uint8
+
+	// nal_unit_type, specifies the type of RBSP data contained in the NAL as
+	// defined in Table 7-1.
+	Type uint8
+
+	// svc_extension_flag, indicates whether a nal_unit_header_svc_extension()
+	// (G.7.3.1.1) or nal_unit_header_mvc_extension() (H.7.3.1.1) will follow next
+	// in the syntax structure.
+	SVCExtensionFlag bool
+
+	// avc_3d_extension_flag, for nal_unit_type = 21, indicates that a
+	// nal_unit_header_mvc_extension() (H.7.3.1.1) or
+	// nal_unit_header_3davc_extension() (J.7.3.1.1) will follow next in syntax
+	// structure.
+	AVC3DExtensionFlag bool
+
+	// nal_unit_header_svc_extension() as defined in section G.7.3.1.1.
+	SVCExtension *SVCExtension
+
+	// nal_unit_header_3davc_extension() as defined in section J.7.3.1.1
+	ThreeDAVCExtension *ThreeDAVCExtension
+
+	// nal_unit_header_mvc_extension() as defined in section H.7.3.1.1).
+	MVCExtension *MVCExtension
+
+	// emulation_prevention_three_byte, equal to 0x03 and is discarded by decoder.
 	EmulationPreventionThreeByte byte
-	rbsp                         []byte
+
+	// rbsp_byte, the raw byte sequence payload data for the NAL.
+	RBSP []byte
 }
 
-func NalUnitHeaderSvcExtension(nalUnit *NalUnit, br *bits.BitReader) error {
+// NewNALUnit parses a network abstraction layer unit from br following the
-	return readFields(br, []field{
+// syntax structure specified in section 7.3.1, and returns as a new NALUnit.
-		{&nalUnit.IdrFlag, "IdrFlag", 1},
+func NewNALUnit(br *bits.BitReader) (*NALUnit, error) {
-		{&nalUnit.PriorityId, "PriorityId", 6},
+	n := &NALUnit{}
-		{&nalUnit.NoInterLayerPredFlag, "NoInterLayerPredFlag", 1},
+	r := newFieldReader(br)
-		{&nalUnit.DependencyId, "DependencyId", 3},
-		{&nalUnit.QualityId, "QualityId", 4},
-		{&nalUnit.TemporalId, "TemporalId", 3},
-		{&nalUnit.UseRefBasePicFlag, "UseRefBasePicFlag", 1},
-		{&nalUnit.DiscardableFlag, "DiscardableFlag", 1},
-		{&nalUnit.OutputFlag, "OutputFlag", 1},
-		{&nalUnit.ReservedThree2Bits, "ReservedThree2Bits", 2},
-	})
-}
 
-func NalUnitHeader3davcExtension(nalUnit *NalUnit, br *bits.BitReader) error {
+	n.ForbiddenZeroBit = uint8(r.readBits(1))
-	return readFields(br, []field{
+	n.RefIdc = uint8(r.readBits(2))
-		{&nalUnit.ViewIdx, "ViewIdx", 8},
+	n.Type = uint8(r.readBits(5))
-		{&nalUnit.DepthFlag, "DepthFlag", 1},
-		{&nalUnit.NonIdrFlag, "NonIdrFlag", 1},
-		{&nalUnit.TemporalId, "TemporalId", 3},
-		{&nalUnit.AnchorPicFlag, "AnchorPicFlag", 1},
-		{&nalUnit.InterViewFlag, "InterViewFlag", 1},
-	})
-}
 
-func NalUnitHeaderMvcExtension(nalUnit *NalUnit, br *bits.BitReader) error {
+	var err error
-	return readFields(br, []field{
+	if n.Type == naluTypePrefixNALU || n.Type == naluTypeSliceLayerExtRBSP || n.Type == naluTypeSliceLayerExtRBSP2 {
-		{&nalUnit.NonIdrFlag, "NonIdrFlag", 1},
+		if n.Type != naluTypeSliceLayerExtRBSP2 {
-		{&nalUnit.PriorityId, "PriorityId", 6},
+			n.SVCExtensionFlag = r.readBits(1) == 1
-		{&nalUnit.ViewId, "ViewId", 10},
-		{&nalUnit.TemporalId, "TemporalId", 3},
-		{&nalUnit.AnchorPicFlag, "AnchorPicFlag", 1},
-		{&nalUnit.InterViewFlag, "InterViewFlag", 1},
-		{&nalUnit.ReservedOneBit, "ReservedOneBit", 1},
-	})
-}
-
-func (n *NalUnit) RBSP() []byte {
-	return n.rbsp
-}
-
-func NewNalUnit(frame []byte, numBytesInNal int) (*NalUnit, error) {
-	logger.Printf("debug: reading %d byte NAL\n", numBytesInNal)
-	nalUnit := NalUnit{
-		NumBytes:    numBytesInNal,
-		HeaderBytes: 1,
-	}
-	// TODO: pass in actual io.Reader to NewBitReader
-	br := bits.NewBitReader(nil)
-
-	err := readFields(br, []field{
-		{&nalUnit.ForbiddenZeroBit, "ForbiddenZeroBit", 1},
-		{&nalUnit.RefIdc, "NalRefIdc", 2},
-		{&nalUnit.Type, "NalUnitType", 5},
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	if nalUnit.Type == 14 || nalUnit.Type == 20 || nalUnit.Type == 21 {
-		if nalUnit.Type != 21 {
-			b, err := br.ReadBits(1)
-			if err != nil {
-				return nil, errors.Wrap(err, "could not read SvcExtensionFlag")
-			}
-			nalUnit.SvcExtensionFlag = int(b)
 		} else {
-			b, err := br.ReadBits(1)
+			n.AVC3DExtensionFlag = r.readBits(1) == 1
+		}
+		if n.SVCExtensionFlag {
+			n.SVCExtension, err = NewSVCExtension(br)
 			if err != nil {
-				return nil, errors.Wrap(err, "could not read Avc3dExtensionFlag")
+				return nil, errors.Wrap(err, "could not parse SVCExtension")
 			}
-			nalUnit.Avc3dExtensionFlag = int(b)
+		} else if n.AVC3DExtensionFlag {
+			n.ThreeDAVCExtension, err = NewThreeDAVCExtension(br)
+			if err != nil {
+				return nil, errors.Wrap(err, "could not parse ThreeDAVCExtension")
 			}
-		if nalUnit.SvcExtensionFlag == 1 {
-			NalUnitHeaderSvcExtension(&nalUnit, br)
-			nalUnit.HeaderBytes += 3
-		} else if nalUnit.Avc3dExtensionFlag == 1 {
-			NalUnitHeader3davcExtension(&nalUnit, br)
-			nalUnit.HeaderBytes += 2
 		} else {
-			NalUnitHeaderMvcExtension(&nalUnit, br)
+			n.MVCExtension, err = NewMVCExtension(br)
-			nalUnit.HeaderBytes += 3
+			if err != nil {
-
+				return nil, errors.Wrap(err, "could not parse MVCExtension")
+			}
 		}
 	}
 
-	logger.Printf("debug: found %d byte header. Reading body\n", nalUnit.HeaderBytes)
+	for moreRBSPData(br) {
-	for i := nalUnit.HeaderBytes; i < nalUnit.NumBytes; i++ {
 		next3Bytes, err := br.PeekBits(24)
-		if err != nil {
+
-			logger.Printf("error: while reading next 3 NAL bytes: %v\n", err)
+		// If PeekBits cannot get 3 bytes, but there still might be 2 bytes left in
-			break
+		// the source, we will get an io.EOF; we wish to ignore this and continue.
+		// The call to moreRBSPData will determine when we have reached the end of
+		// the NAL unit.
+		if err != nil && errors.Cause(err) != io.EOF {
+			return nil, errors.Wrap(err, "could not Peek next 3 bytes")
 		}
-		// Little odd, the err above and the i+2 check might be synonyms
+
-		if i+2 < nalUnit.NumBytes && next3Bytes == 0x000003 {
+		if next3Bytes == 0x000003 {
 			for j := 0; j < 2; j++ {
-				rbspByte, err := br.ReadBits(8)
+				rbspByte := byte(r.readBits(8))
-				if err != nil {
+				n.RBSP = append(n.RBSP, byte(rbspByte))
-					return nil, errors.Wrap(err, "could not read rbspByte")
 			}
-				nalUnit.rbsp = append(nalUnit.rbsp, byte(rbspByte))
-			}
-			i += 2
 
 			// Read Emulation prevention three byte.
-			eptByte, err := br.ReadBits(8)
+			n.EmulationPreventionThreeByte = byte(r.readBits(8))
-			if err != nil {
-				return nil, errors.Wrap(err, "could not read eptByte")
-			}
-			nalUnit.EmulationPreventionThreeByte = byte(eptByte)
 		} else {
-			if b, err := br.ReadBits(8); err == nil {
+			n.RBSP = append(n.RBSP, byte(r.readBits(8)))
-				nalUnit.rbsp = append(nalUnit.rbsp, byte(b))
-			} else {
-				logger.Printf("error: while reading byte %d of %d nal bytes: %v\n", i, nalUnit.NumBytes, err)
-				break
-			}
 		}
 	}
 
-	// nalUnit.rbsp = frame[nalUnit.HeaderBytes:]
+	if r.err() != nil {
-	logger.Printf("info: decoded %s NAL with %d RBSP bytes\n", NALUnitType[nalUnit.Type], len(nalUnit.rbsp))
+		return nil, fmt.Errorf("fieldReader error: %v", r.err())
-	return &nalUnit, nil
+	}
+
+	return n, nil
 }

codec/h264/h264dec/read.go

@@ -63,7 +63,7 @@ func (h *H264Reader) Start() {
 		switch nalUnit.Type {
 		case naluTypeSPS:
 			// TODO: handle this error
-			sps, _ := NewSPS(nalUnit.rbsp, false)
+			sps, _ := NewSPS(nalUnit.RBSP, false)
 			h.VideoStreams = append(
 				h.VideoStreams,
 				&VideoStream{SPS: sps},
@@ -71,20 +71,20 @@ func (h *H264Reader) Start() {
 		case naluTypePPS:
 			videoStream := h.VideoStreams[len(h.VideoStreams)-1]
 			// TODO: handle this error
-			videoStream.PPS, _ = NewPPS(videoStream.SPS, nalUnit.RBSP(), false)
+			videoStream.PPS, _ = NewPPS(videoStream.SPS, nalUnit.RBSP, false)
 		case naluTypeSliceIDRPicture:
 			fallthrough
 		case naluTypeSliceNonIDRPicture:
 			videoStream := h.VideoStreams[len(h.VideoStreams)-1]
 			logger.Printf("info: frame number %d\n", len(videoStream.Slices))
 			// TODO: handle this error
-			sliceContext, _ := NewSliceContext(videoStream, nalUnit, nalUnit.RBSP(), true)
+			sliceContext, _ := NewSliceContext(videoStream, nalUnit, nalUnit.RBSP, true)
 			videoStream.Slices = append(videoStream.Slices, sliceContext)
 		}
 	}
 }
 
-func (r *H264Reader) readNalUnit() (*NalUnit, *bits.BitReader, error) {
+func (r *H264Reader) readNalUnit() (*NALUnit, *bits.BitReader, error) {
 	// Read to start of NAL
 	logger.Printf("debug: Seeking NAL %d start\n", len(r.NalUnits))
 
@@ -131,7 +131,7 @@ func (r *H264Reader) readNalUnit() (*NalUnit, *bits.BitReader, error) {
 	r.NalUnits = append(r.NalUnits, nalUnitReader)
 	// TODO: this should really take an io.Reader rather than []byte. Need to fix nil
 	// once this is fixed.
-	nalUnit, err := NewNalUnit(nil, 0)
+	nalUnit, err := NewNALUnit(nil)
 	if err != nil {
 		return nil, nil, errors.Wrap(err, "cannot create new nal unit")
 	}

codec/h264/h264dec/slice.go

@@ -23,7 +23,7 @@ type VideoStream struct {
 	Slices []*SliceContext
 }
 type SliceContext struct {
-	*NalUnit
+	*NALUnit
 	*SPS
 	*PPS
 	*Slice
@@ -240,12 +240,12 @@ func CodedBlockPatternChroma(data *SliceData) int {
 
 // dependencyId see Annex G.8.8.1
 // Also G7.3.1.1 nal_unit_header_svc_extension
-func DQId(nalUnit *NalUnit) int {
+func DQId(nalUnit *NALUnit) int {
-	return (nalUnit.DependencyId << 4) + nalUnit.QualityId
+	return int((nalUnit.SVCExtension.DependencyID << 4)) + int(nalUnit.SVCExtension.QualityID)
 }
 
 // Annex G p527
-func NumMbPart(nalUnit *NalUnit, sps *SPS, header *SliceHeader, data *SliceData) int {
+func NumMbPart(nalUnit *NALUnit, sps *SPS, header *SliceHeader, data *SliceData) int {
 	sliceType := sliceTypeMap[header.SliceType]
 	numMbPart := 0
 	if MbTypeName(sliceType, CurrMbAddr(sps, header)) == "B_SKIP" || MbTypeName(sliceType, CurrMbAddr(sps, header)) == "B_Direct_16x16" {
@@ -381,7 +381,7 @@ func MbPred(sliceContext *SliceContext, br *bits.BitReader, rbsp []byte) error {
 		}
 
 	} else if mbPartPredMode != direct {
-		for mbPartIdx := 0; mbPartIdx < NumMbPart(sliceContext.NalUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data); mbPartIdx++ {
+		for mbPartIdx := 0; mbPartIdx < NumMbPart(sliceContext.NALUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data); mbPartIdx++ {
 			sliceContext.Update(sliceContext.Slice.Header, sliceContext.Slice.Data)
 			m, err := MbPartPredMode(sliceContext.Slice.Data, sliceType, sliceContext.Slice.Data.MbType, mbPartIdx)
 			if err != nil {
@@ -417,7 +417,7 @@ func MbPred(sliceContext *SliceContext, br *bits.BitReader, rbsp []byte) error {
 				}
 			}
 		}
-		for mbPartIdx := 0; mbPartIdx < NumMbPart(sliceContext.NalUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data); mbPartIdx++ {
+		for mbPartIdx := 0; mbPartIdx < NumMbPart(sliceContext.NALUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data); mbPartIdx++ {
 			m, err := MbPartPredMode(sliceContext.Slice.Data, sliceType, sliceContext.Slice.Data.MbType, mbPartIdx)
 			if err != nil {
 				return errors.Wrap(err, fmt.Sprintf("could not get mbPartPredMode for loop 2 mbPartIdx: %d", mbPartIdx))
@@ -456,7 +456,7 @@ func MbPred(sliceContext *SliceContext, br *bits.BitReader, rbsp []byte) error {
 				}
 			}
 		}
-		for mbPartIdx := 0; mbPartIdx < NumMbPart(sliceContext.NalUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data); mbPartIdx++ {
+		for mbPartIdx := 0; mbPartIdx < NumMbPart(sliceContext.NALUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data); mbPartIdx++ {
 			sliceContext.Update(sliceContext.Slice.Header, sliceContext.Slice.Data)
 			m, err := MbPartPredMode(sliceContext.Slice.Data, sliceType, sliceContext.Slice.Data.MbType, mbPartIdx)
 			if err != nil {
@@ -815,7 +815,7 @@ func NewSliceData(sliceContext *SliceContext, br *bits.BitReader) (*SliceData, e
 				if err != nil {
 					return nil, errors.Wrap(err, "could not get mbPartPredMode")
 				}
-				if sliceContext.Slice.Data.MbTypeName == "I_NxN" && m != intra16x16 && NumMbPart(sliceContext.NalUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data) == 4 {
+				if sliceContext.Slice.Data.MbTypeName == "I_NxN" && m != intra16x16 && NumMbPart(sliceContext.NALUnit, sliceContext.SPS, sliceContext.Slice.Header, sliceContext.Slice.Data) == 4 {
 					logger.Printf("\tTODO: subMbPred\n")
 					/*
 						subMbType := SubMbPred(sliceContext.Slice.Data.MbType)
@@ -945,11 +945,11 @@ func NewSliceData(sliceContext *SliceContext, br *bits.BitReader) (*SliceData, e
 func (c *SliceContext) Update(header *SliceHeader, data *SliceData) {
 	c.Slice = &Slice{Header: header, Data: data}
 }
-func NewSliceContext(videoStream *VideoStream, nalUnit *NalUnit, rbsp []byte, showPacket bool) (*SliceContext, error) {
+func NewSliceContext(videoStream *VideoStream, nalUnit *NALUnit, rbsp []byte, showPacket bool) (*SliceContext, error) {
 	var err error
 	sps := videoStream.SPS
 	pps := videoStream.PPS
-	logger.Printf("debug: %s RBSP %d bytes %d bits == \n", NALUnitType[nalUnit.Type], len(rbsp), len(rbsp)*8)
+	logger.Printf("debug: %s RBSP %d bytes %d bits == \n", NALUnitType[int(nalUnit.Type)], len(rbsp), len(rbsp)*8)
 	logger.Printf("debug: \t%#v\n", rbsp[0:8])
 	var idrPic bool
 	if nalUnit.Type == 5 {
@@ -974,7 +974,7 @@ func NewSliceContext(videoStream *VideoStream, nalUnit *NalUnit, rbsp []byte, sh
 	}
 
 	sliceType := sliceTypeMap[header.SliceType]
-	logger.Printf("debug: %s (%s) slice of %d bytes\n", NALUnitType[nalUnit.Type], sliceType, len(rbsp))
+	logger.Printf("debug: %s (%s) slice of %d bytes\n", NALUnitType[int(nalUnit.Type)], sliceType, len(rbsp))
 	header.PPSID, err = readUe(br)
 	if err != nil {
 		return nil, errors.Wrap(err, "could not parse PPSID")
@@ -1350,7 +1350,7 @@ func NewSliceContext(videoStream *VideoStream, nalUnit *NalUnit, rbsp []byte, sh
 	}
 
 	sliceContext := &SliceContext{
-		NalUnit: nalUnit,
+		NALUnit: nalUnit,
 		SPS:     sps,
 		PPS:     pps,
 		Slice: &Slice{