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slice.go
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slice.go
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package avc
import (
"bytes"
"errors"
"math"
"github.com/jaypadia-frame/mp4ff/bits"
)
var ErrNoSliceHeader = errors.New("No slice header")
var ErrInvalidSliceType = errors.New("Invalid slice type")
var ErrTooFewBytesToParse = errors.New("Too few bytes to parse symbol")
var ErrParserNotImplemented = errors.New("Parser not implemented")
type SliceType uint
func (s SliceType) String() string {
switch s {
case SLICE_I:
return "I"
case SLICE_P:
return "P"
case SLICE_B:
return "B"
default:
return ""
}
}
const (
SLICE_P = SliceType(0)
SLICE_B = SliceType(1)
SLICE_I = SliceType(2)
SLICE_SP = SliceType(3)
SLICE_SI = SliceType(4)
)
// SliceHeader - AVC Slice header
type SliceHeader struct {
FirstMbInSlice uint // ue(v)
SliceType SliceType // ue(v)
PicParameterSetID uint // ue(v)
ColourPlaneID uint // u(2)
FrameNum uint // u(v) - uses Log2MaxFrameNumMinus4
FieldPicFlag bool // u(1)
BottomFieldFlag bool // u(1)
IDRPicID uint // ue(v)
PicOrderCntLSB uint // u(v) - TODO: what does 'v' depend on?
DeltaPicOrderCntBottom int // se(v)
DeltaPicOrderCnt [2]int // se(v)
RedundantPicCnt uint // ue(v)
DirectSpatialMVPredFlag bool // u(1)
NumRefIdxActiveOverrideFlag bool // u(1)
NumRefIdxL0ActiveMinus1 uint // ue(v)
NumRefIdxL1ActiveMinus1 uint // ue(v)
// Ref Pic List Modification MVC not implmented
RefPicListModification *RefPicListModification
PredWeightTable *PredWeightTable
DecRefPicMarking *DecRefPicMarking
CabacInitIDC uint // ue(v)
SliceQPDelta int // se(v)
SPForSwitchFlag bool // u(1)
SliceQSDelta int // se(v)
DisableDeblockingFilterIDC uint // ue(v)
SliceAlphaC0OffsetDev2 int // se(v)
SliceBetaOffsetDev2 int // se(v)
SliceGroupChangeCycle uint // u(v) - TODO: what does 'v' depend on?
}
// RefPicListModification - AVC Ref Pic list modification at slice level
type RefPicListModification struct {
RefPicListModificationFlagL0 bool // u(1)
RefPicListModificationFlagL1 bool // u(1)
PerEntryParams []PerEntryRefPicListModParams
}
// PerEntryRefPicListModParams - Ref Pic List Mod params per each entry
type PerEntryRefPicListModParams struct {
ModificationOfPicNumsIDC uint // ue(v)
AbsDiffPicNumMinus1 uint // ue(v)
LongTermPicNum uint // ue(v)
}
// PredWeightTable - AVC Prediction Weight Table in slice header
type PredWeightTable struct {
LumaLog2WeightDenom uint // ue(v)
ChromaLog2WeightDenom uint // ue(v)
LumaWeightL0Flag bool // u(1)
LumaWeightL0 []int // se(v)
LumaOffsetL0 []int // se(v)
ChromaWeightL0Flag bool // u(1)
ChromaWeightL0 [][]int // se(v)
ChromaOffsetL0 [][]int // se(v)
LumaWeightL1Flag bool // u(1)
LumaWeightL1 []int // se(v)
LumaOffsetL1 []int // se(v)
ChromaWeightL1Flag bool // u(1)
ChromaWeightL1 [][]int // se(v)
ChromaOffsetL1 [][]int // se(v)
}
// DecRefPicMarking - Decoded Reference Picture Marking Syntax
type DecRefPicMarking struct {
NoOutputOfPriorPicsFlag bool // u(1)
LongTermReferenceFlag bool // u(1)
AdaptiveRefPicMarkingModeFlag bool // u(1)
AdaptiveRefPicMarkingParams []AdaptiveMemCtrlDecRefPicMarkingParams
}
// AdaptiveMemCtrlDecRefPicMarkingParams - Used as explained in 8.2.5.4
type AdaptiveMemCtrlDecRefPicMarkingParams struct {
MemoryManagementControlOperation uint // ue(v)
DifferenceOfPicNumsMinus1 uint // ue(v)
LongTermPicNum uint // ue(v)
LongTermFrameIdx uint // ue(v)
MaxLongTermFrameIdxPlus1 uint // ue(V)
}
// GetSliceTypeFromNALU - parse slice header to get slice type in interval 0 to 4
// This function is no longer necessary after the ParseSliceHeader is added
func GetSliceTypeFromNALU(data []byte) (sliceType SliceType, err error) {
if len(data) <= 1 {
err = ErrTooFewBytesToParse
return
}
naluType := GetNaluType(data[0])
switch naluType {
case 1, 2, 5, 19:
// slice_layer_without_partitioning_rbsp
// slice_data_partition_a_layer_rbsp
default:
err = ErrNoSliceHeader
return
}
r := bits.NewEBSPReader(bytes.NewReader((data[1:])))
// first_mb_in_slice
if _, err = r.ReadExpGolomb(); err != nil {
return
}
// slice_type
var st uint
if st, err = r.ReadExpGolomb(); err != nil {
return
}
sliceType = SliceType(st)
if sliceType > 9 {
err = ErrInvalidSliceType
return
}
if sliceType >= 5 {
sliceType -= 5 // The same type is repeated twice to tell if all slices in picture are the same
}
return
}
// ParseSliceHeader - Parse AVC Slice Header starting with NAL header
func ParseSliceHeader(data []byte, sps *SPS, pps *PPS) (*SliceHeader, int, error) {
avcsh := &SliceHeader{}
var err error
rd := bytes.NewReader(data)
r := bits.NewEBSPReader(rd)
// Note! First byte is NAL Header
nalHdr, err := r.Read(8)
if err != nil {
return nil, r.NrBytesRead(), err
}
nalType := GetNaluType(byte(nalHdr))
if !sliceHeaderExpected(nalType) {
return nil, r.NrBytesRead(), ErrNoSliceHeader
}
avcsh.FirstMbInSlice, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
sliceType, err := r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
avcsh.SliceType, err = setSliceType(sliceType)
if err != nil {
return nil, r.NrBytesRead(), err
}
avcsh.PicParameterSetID, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
if sps.SeparateColourPlaneFlag {
avcsh.ColourPlaneID, err = r.Read(2)
if err != nil {
return nil, r.NrBytesRead(), err
}
}
avcsh.FrameNum, err = r.Read(int(sps.Log2MaxFrameNumMinus4) + 4)
if err != nil {
return nil, r.NrBytesRead(), err
}
if !sps.FrameMbsOnlyFlag {
avcsh.FieldPicFlag, err = r.ReadFlag()
if err != nil {
return nil, r.NrBytesRead(), err
}
if avcsh.FieldPicFlag {
avcsh.BottomFieldFlag, err = r.ReadFlag()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
}
if getIDRPicFlag(nalType) {
avcsh.IDRPicID, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if sps.PicOrderCntType == 0 {
avcsh.PicOrderCntLSB, err = r.Read(int(sps.Log2MaxPicOrderCntLsbMinus4) + 4)
if err != nil {
return nil, r.NrBytesRead(), err
}
if pps.BottomFieldPicOrderInFramePresentFlag && !avcsh.FieldPicFlag {
avcsh.DeltaPicOrderCntBottom, err = r.ReadSignedGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
}
if sps.PicOrderCntType == 1 && !sps.DeltaPicOrderAlwaysZeroFlag {
avcsh.DeltaPicOrderCnt[0], err = r.ReadSignedGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
if pps.BottomFieldPicOrderInFramePresentFlag && !avcsh.FieldPicFlag {
avcsh.DeltaPicOrderCnt[1], err = r.ReadSignedGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
}
if pps.RedundantPicCntPresentFlag {
avcsh.RedundantPicCnt, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if avcsh.SliceType == SLICE_B {
avcsh.DirectSpatialMVPredFlag, err = r.ReadFlag()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if avcsh.SliceType == SLICE_P || avcsh.SliceType == SLICE_SP || avcsh.SliceType == SLICE_B {
avcsh.NumRefIdxActiveOverrideFlag, err = r.ReadFlag()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if avcsh.NumRefIdxActiveOverrideFlag {
avcsh.NumRefIdxL0ActiveMinus1, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
if avcsh.SliceType == SLICE_B {
avcsh.NumRefIdxL1ActiveMinus1, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
} else {
avcsh.NumRefIdxL0ActiveMinus1 = pps.NumRefIdxI0DefaultActiveMinus1
avcsh.NumRefIdxL1ActiveMinus1 = pps.NumRefIdxI1DefaultActiveMinus1
}
if nalType == NaluType(20) || nalType == NaluType(21) {
// MVC not implemented
return nil, r.NrBytesRead(), ErrParserNotImplemented
} else {
avcsh.RefPicListModification, err = ParseRefPicListModification(r, avcsh)
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if (pps.WeightedPredFlag && (avcsh.SliceType == SLICE_P || avcsh.SliceType == SLICE_SP)) ||
(pps.WeightedBipredIDC == 1 && avcsh.SliceType == SLICE_B) {
avcsh.PredWeightTable, err = ParsePredWeightTable(r, sps, avcsh)
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if GetNalRefIDC(byte(nalHdr)) != 0 {
avcsh.DecRefPicMarking, err = ParseDecRefPicMarking(r, nalType)
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if pps.EntropyCodingModeFlag && avcsh.SliceType != SLICE_I && avcsh.SliceType != SLICE_SI {
avcsh.CabacInitIDC, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
avcsh.SliceQPDelta, err = r.ReadSignedGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
if avcsh.SliceType == SLICE_SP || avcsh.SliceType == SLICE_SI {
if avcsh.SliceType == SLICE_SP {
avcsh.SPForSwitchFlag, err = r.ReadFlag()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
avcsh.SliceQSDelta, err = r.ReadSignedGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
if pps.DeblockingFilterControlPresentFlag {
avcsh.DisableDeblockingFilterIDC, err = r.ReadExpGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
if avcsh.DisableDeblockingFilterIDC != 1 {
avcsh.SliceAlphaC0OffsetDev2, err = r.ReadSignedGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
avcsh.SliceBetaOffsetDev2, err = r.ReadSignedGolomb()
if err != nil {
return nil, r.NrBytesRead(), err
}
}
}
if pps.NumSliceGroupsMinus1 > 0 && pps.SliceGroupMapType >= 3 && pps.SliceGroupMapType <= 5 {
// based on equation 7-35 H.264 spec
sgccNumBits := math.Ceil(math.Log2(float64((pps.PicSizeInMapUnitsMinus1+1)/(pps.SliceGroupChangeRateMinus1+1) + 1)))
avcsh.SliceGroupChangeCycle, err = r.Read(int(sgccNumBits))
if err != nil {
return nil, r.NrBytesRead(), err
}
}
return avcsh, r.NrBytesRead(), nil
}
// ParseRefPicListModification - AVC Ref Pic list modification parser using bits r
func ParseRefPicListModification(r *bits.EBSPReader, avcsh *SliceHeader) (*RefPicListModification, error) {
rplm := &RefPicListModification{}
var err error
if avcsh.SliceType%5 != 2 && avcsh.SliceType%5 != 4 {
rplm.RefPicListModificationFlagL0, err = r.ReadFlag()
if err != nil {
return nil, err
}
if rplm.RefPicListModificationFlagL0 {
var mopni int
for ok := true; ok; ok = (mopni != 3) {
rplmEntry := PerEntryRefPicListModParams{}
rplmEntry.ModificationOfPicNumsIDC, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
mopni = int(rplmEntry.ModificationOfPicNumsIDC)
if rplmEntry.ModificationOfPicNumsIDC == 0 || rplmEntry.ModificationOfPicNumsIDC == 1 {
rplmEntry.AbsDiffPicNumMinus1, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
} else if rplmEntry.ModificationOfPicNumsIDC == 2 {
rplmEntry.LongTermPicNum, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
}
rplm.PerEntryParams = append(rplm.PerEntryParams, rplmEntry)
}
}
}
if avcsh.SliceType%5 == 1 {
rplm.RefPicListModificationFlagL1, err = r.ReadFlag()
if err != nil {
return nil, err
}
if rplm.RefPicListModificationFlagL0 {
var mopni int
for ok := true; ok; ok = (mopni != 3) {
rplmEntry := PerEntryRefPicListModParams{}
rplmEntry.ModificationOfPicNumsIDC, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
mopni = int(rplmEntry.ModificationOfPicNumsIDC)
if rplmEntry.ModificationOfPicNumsIDC == 0 || rplmEntry.ModificationOfPicNumsIDC == 1 {
rplmEntry.AbsDiffPicNumMinus1, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
} else if rplmEntry.ModificationOfPicNumsIDC == 2 {
rplmEntry.LongTermPicNum, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
}
rplm.PerEntryParams = append(rplm.PerEntryParams, rplmEntry)
}
}
}
return rplm, nil
}
// ParsePredWeightTable - AVC Slice Prediction Weight Table parser using bits r
func ParsePredWeightTable(r *bits.EBSPReader, sps *SPS, avcsh *SliceHeader) (*PredWeightTable, error) {
pwt := &PredWeightTable{}
var err error
pwt.LumaLog2WeightDenom, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
if getChromaArrayType(sps) != 0 {
pwt.ChromaLog2WeightDenom, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
}
for i := uint(0); i <= avcsh.NumRefIdxL0ActiveMinus1; i++ {
pwt.LumaWeightL0Flag, err = r.ReadFlag()
if err != nil {
return nil, err
}
if pwt.LumaWeightL0Flag {
lumaWeightL0, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
lumaOffsetL0, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
pwt.LumaWeightL0 = append(pwt.LumaWeightL0, lumaWeightL0)
pwt.LumaOffsetL0 = append(pwt.LumaOffsetL0, lumaOffsetL0)
}
if getChromaArrayType(sps) != 0 {
pwt.ChromaWeightL0Flag, err = r.ReadFlag()
if err != nil {
return nil, err
}
if pwt.ChromaWeightL0Flag {
var chromaWeightL0, chromaOffsetL0 []int
for j := 0; j < 2; j++ {
chromaWeight, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
chromaOffset, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
chromaWeightL0 = append(chromaWeightL0, chromaWeight)
chromaOffsetL0 = append(chromaOffsetL0, chromaOffset)
}
pwt.ChromaWeightL0 = append(pwt.ChromaWeightL0, chromaWeightL0)
pwt.ChromaOffsetL0 = append(pwt.ChromaWeightL0, chromaOffsetL0)
}
}
}
if avcsh.SliceType%5 == 1 {
for i := uint(0); i <= avcsh.NumRefIdxL1ActiveMinus1; i++ {
pwt.LumaWeightL1Flag, err = r.ReadFlag()
if err != nil {
return nil, err
}
if pwt.LumaWeightL1Flag {
lumaWeightL1, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
lumaOffsetL1, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
pwt.LumaWeightL1 = append(pwt.LumaWeightL1, lumaWeightL1)
pwt.LumaOffsetL1 = append(pwt.LumaWeightL1, lumaOffsetL1)
}
if getChromaArrayType(sps) != 0 {
pwt.ChromaWeightL1Flag, err = r.ReadFlag()
if err != nil {
return nil, err
}
if pwt.ChromaWeightL1Flag {
var chromaWeightL1, chromaOffsetL1 []int
for j := 0; j < 2; j++ {
chromaWeight, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
chromaOffset, err := r.ReadSignedGolomb()
if err != nil {
return nil, err
}
chromaWeightL1 = append(chromaWeightL1, chromaWeight)
chromaOffsetL1 = append(chromaOffsetL1, chromaOffset)
}
pwt.ChromaWeightL1 = append(pwt.ChromaWeightL1, chromaWeightL1)
pwt.ChromaOffsetL1 = append(pwt.ChromaWeightL1, chromaOffsetL1)
}
}
}
}
return pwt, nil
}
// ParseDecRefPicMarking - AVC Slice Decoded Reference Picture Marking parser using bits r
func ParseDecRefPicMarking(r *bits.EBSPReader, naluType NaluType) (*DecRefPicMarking, error) {
rpm := &DecRefPicMarking{}
var err error
if getIDRPicFlag(naluType) {
rpm.NoOutputOfPriorPicsFlag, err = r.ReadFlag()
if err != nil {
return nil, err
}
rpm.LongTermReferenceFlag, err = r.ReadFlag()
if err != nil {
return nil, err
}
} else {
rpm.AdaptiveRefPicMarkingModeFlag, err = r.ReadFlag()
if err != nil {
return nil, err
}
if rpm.AdaptiveRefPicMarkingModeFlag {
var mmco int
for ok := true; ok; ok = (mmco != 0) {
arpmParams := AdaptiveMemCtrlDecRefPicMarkingParams{}
arpmParams.MemoryManagementControlOperation, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
mmco = int(arpmParams.MemoryManagementControlOperation)
if mmco == 1 || mmco == 3 {
arpmParams.DifferenceOfPicNumsMinus1, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
}
if mmco == 2 {
arpmParams.LongTermPicNum, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
}
if mmco == 3 || mmco == 6 {
arpmParams.LongTermFrameIdx, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
}
if mmco == 4 {
arpmParams.MaxLongTermFrameIdxPlus1, err = r.ReadExpGolomb()
if err != nil {
return nil, err
}
}
rpm.AdaptiveRefPicMarkingParams = append(rpm.AdaptiveRefPicMarkingParams, arpmParams)
}
}
}
return rpm, nil
}
// getIDRPicFlag - Sets IDR Pic flag based on H.264 Spec equation 7-1
// The equation sets value as 1/0, but uses like a bool in the tabular syntax
func getIDRPicFlag(naluType NaluType) bool {
if naluType == NALU_IDR {
return true
}
return false
}
// getChromaArrayType - Sets ChromaArrayType based on the SeparateColourPlaneFlag from SPS
// this is based on H.264 spec 7.4.2.1.1
func getChromaArrayType(sps *SPS) uint {
if sps.SeparateColourPlaneFlag {
return 0
}
return sps.ChromaFormatIDC
}
// sliceHeaderExpected - Tells if a slice header should be expected: Nal types: 1,2,5,19
func sliceHeaderExpected(naluType NaluType) bool {
switch naluType {
case 1, 2, 5, 19:
// slice_layer_without_partitioning_rbsp
// slice_data_partition_a_layer_rbsp
return true
default:
return false
}
}
// setSliceType validates the value and sets the type based on numerical value
func setSliceType(sliceType uint) (SliceType, error) {
if sliceType > 9 {
return SliceType(sliceType), ErrInvalidSliceType
}
if sliceType >= 5 {
sliceType -= 5 // The same type is repeated twice to tell if all slices in picture are the same
}
return SliceType(sliceType), nil
}