mirror of https://bitbucket.org/ausocean/av.git
Merged in picture-order-count (pull request #249)
codec/h264/h264dec/decode.go: decoding process for picture order count Approved-by: Alan Noble <anoble@gmail.com>
This commit is contained in:
Saxon Milton
commit
f8f78947f9
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@ -23,3 +23,169 @@ LICENSE
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*/
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package h264dec
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import (
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"errors"
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"fmt"
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)
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// NB: this is a placeholder.
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func decode(vid *VideoStream, ctx *SliceContext) error {
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var err error
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vid.topFieldOrderCnt, vid.bottomFieldOrderCnt, err = decodePicOrderCnt(vid, ctx)
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if err != nil {
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return fmt.Errorf("could not derive topFieldOrderCnt and bottomFieldOrderCnt, failed with error: %v", err)
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}
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// According to 8.2.1 after decoding picture.
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if ctx.elements[0].MemoryManagementControlOperation == 5 {
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tempPicOrderCnt := picOrderCnt(ctx)
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vid.topFieldOrderCnt = vid.topFieldOrderCnt - tempPicOrderCnt
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vid.bottomFieldOrderCnt = vid.bottomFieldOrderCnt - tempPicOrderCnt
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}
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return nil
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}
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// TODO: complete this. Unsure how to determine if pic is frame or a
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// complementary field pair.
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// picOrderCnt as defined by section 8.2.1.
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func picOrderCnt(ctx *SliceContext) int {
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panic("not implemented")
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}
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// decodePicOrderCnt derives topFieldOrderCnt and bottomFieldOrderCnt based
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// on the PicOrderCntType using the process defined in section 8.2.1 of the
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// specifications.
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func decodePicOrderCnt(vid *VideoStream, ctx *SliceContext) (topFieldOrderCnt, bottomFieldOrderCnt int, err error) {
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// There are some steps listed in 8.2.1 regarding cases when not an IDR frame,
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// but we're not yet dealing with that.
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// TODO: write steps dealing with not IDR frame.
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if !vid.idrPicFlag {
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panic("not implemented")
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}
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switch ctx.PicOrderCountType {
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case 0:
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topFieldOrderCnt, bottomFieldOrderCnt = decodePicOrderCntType0(vid, ctx)
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case 1:
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topFieldOrderCnt, bottomFieldOrderCnt = decodePicOrderCntType1(vid, ctx)
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case 2:
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topFieldOrderCnt, bottomFieldOrderCnt = decodePicOrderCntType2(vid, ctx)
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default:
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err = errors.New("invalid PicOrderCountType")
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}
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// TODO: check DiffPicOrderCnt( picA, picB ) once picOrderCnt( picX ) is
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// worked out.
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return
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}
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// picOrderCntType0 is used to return topFieldOrderCnt and bottomFieldOrderCnt
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// when pic_order_cnt_type i.e vid.PicOrderCntType == 0, using the process
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// defined in section 8.2.1.1 of the specifications. If topFieldOrderCnt or
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// bottomFieldOrderCnt are -1 they are unset.
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func decodePicOrderCntType0(vid *VideoStream, ctx *SliceContext) (topFieldOrderCnt, bottomFieldOrderCnt int) {
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prevPicOrderCntMsb, prevPicOrderCntLsb := 0, 0
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topFieldOrderCnt, bottomFieldOrderCnt = -1, -1
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// NB: We're currently only handling IDRs so panic.
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if !vid.idrPicFlag {
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panic("not implemented")
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}
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vid.picOrderCntMsb = prevPicOrderCntMsb
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if ctx.PicOrderCntLsb < prevPicOrderCntLsb && (prevPicOrderCntLsb-ctx.PicOrderCntLsb) >= (vid.maxPicOrderCntLsb/2) {
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vid.picOrderCntMsb = prevPicOrderCntMsb + vid.maxPicOrderCntLsb
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} else if ctx.PicOrderCntLsb > prevPicOrderCntLsb && (ctx.PicOrderCntLsb-prevPicOrderCntLsb) > (vid.maxPicOrderCntLsb/2) {
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vid.picOrderCntMsb = prevPicOrderCntMsb - vid.maxPicOrderCntLsb
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}
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if !ctx.BottomField {
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topFieldOrderCnt = vid.picOrderCntMsb + ctx.PicOrderCntLsb
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} else if ctx.FieldPic {
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bottomFieldOrderCnt = vid.picOrderCntMsb + ctx.PicOrderCntLsb
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} else {
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bottomFieldOrderCnt = topFieldOrderCnt + ctx.DeltaPicOrderCntBottom
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}
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return
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}
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// picOrderCntType1 is used to return topFieldOrderCnt and bottomFieldOrderCnt
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// when vic.PicOrderCntType == 1 according to logic defined in section 8.2.1.2
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// of the specifications. If topFieldOrderCnt or bottomFieldOrderCnt are -1,
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// then they are considered unset.
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func decodePicOrderCntType1(vid *VideoStream, ctx *SliceContext) (topFieldOrderCnt, bottomFieldOrderCnt int) {
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topFieldOrderCnt, bottomFieldOrderCnt = -1, -1
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// TODO: this will be prevFrameNum when we do frames other than IDR.
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_ = vid.priorPic.FrameNum
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if !vid.idrPicFlag {
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panic("not implemented")
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}
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vid.frameNumOffset = 0
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absFrameNum := 0
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if ctx.NumRefFramesInPicOrderCntCycle != 0 {
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absFrameNum = vid.frameNumOffset + ctx.FrameNum
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}
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if ctx.RefIdc == 0 && absFrameNum > 0 {
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absFrameNum = absFrameNum - 1
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}
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var expectedPicOrderCnt int
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if absFrameNum > 0 {
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picOrderCntCycleCnt := (absFrameNum - 1) / int(ctx.NumRefFramesInPicOrderCntCycle)
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frameNumInPicOrderCntCycle := (absFrameNum - 1) % int(ctx.NumRefFramesInPicOrderCntCycle)
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expectedPicOrderCnt = picOrderCntCycleCnt * vid.expectedDeltaPerPicOrderCntCycle
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for i := 0; i <= frameNumInPicOrderCntCycle; i++ {
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expectedPicOrderCnt = expectedPicOrderCnt + ctx.OffsetForRefFrameList[i]
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}
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}
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if ctx.RefIdc == 0 {
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expectedPicOrderCnt = expectedPicOrderCnt + int(ctx.OffsetForNonRefPic)
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}
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if !ctx.FieldPic {
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topFieldOrderCnt = expectedPicOrderCnt + ctx.DeltaPicOrderCnt[0]
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bottomFieldOrderCnt = topFieldOrderCnt + int(ctx.OffsetForTopToBottomField) + ctx.DeltaPicOrderCnt[1]
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} else if ctx.BottomField {
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bottomFieldOrderCnt = expectedPicOrderCnt + int(ctx.OffsetForTopToBottomField) + ctx.DeltaPicOrderCnt[0]
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} else {
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topFieldOrderCnt = expectedPicOrderCnt + ctx.DeltaPicOrderCnt[0]
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}
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return
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}
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// picOrderCntType2 is used to return topFieldOrderCnt and bottomFieldOrderCnt
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// when vic.PicOrderCntType == 1 according to logic defined in section 8.2.1.3
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// of the specifications. If topFieldOrderCnt or bottomFieldOrderCnt are -1,
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// then they are considered unset.
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func decodePicOrderCntType2(vid *VideoStream, ctx *SliceContext) (topFieldOrderCnt, bottomFieldOrderCnt int) {
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topFieldOrderCnt, bottomFieldOrderCnt = -1, -1
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// TODO: this will be prevFrameNum when we do frames other than IDR.
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_ = vid.priorPic.FrameNum
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if !vid.idrPicFlag {
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panic("not implemented")
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}
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vid.frameNumOffset = 0
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// TODO: handle tempPicOrderCnt calculation for when not IDR.
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var tempPicOrderCnt int
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if !ctx.FieldPic {
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topFieldOrderCnt = tempPicOrderCnt
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bottomFieldOrderCnt = tempPicOrderCnt
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} else if ctx.BottomField {
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bottomFieldOrderCnt = tempPicOrderCnt
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} else {
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topFieldOrderCnt = tempPicOrderCnt
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}
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return
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}
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@ -35,15 +35,33 @@ const (
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chroma444
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)
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type picture struct {
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*SliceContext
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isIDR bool
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isBottomField bool
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isTopField bool
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}
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type VideoStream struct {
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*SPS
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*PPS
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Slices []*SliceContext
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ChromaArrayType int
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priorPic *picture
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currPic *picture
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maxPicOrderCntLsb int
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picOrderCntMsb int
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idrPicFlag bool
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frameNumOffset int
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expectedDeltaPerPicOrderCntCycle int
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topFieldOrderCnt int
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bottomFieldOrderCnt int
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}
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type SliceContext struct {
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*SPS
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*PPS
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*NALUnit
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*Slice
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chromaArrayType int
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