mirror of
https://github.com/wader/fq.git
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131 lines
4.6 KiB
Go
131 lines
4.6 KiB
Go
package mpeg
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// TODO: unescape configurable? merge with AVC_NAL? merge with HEVC?
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import (
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"github.com/wader/fq/format"
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"github.com/wader/fq/format/registry"
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"github.com/wader/fq/internal/mathextra"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/scalar"
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)
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var avcSPSFormat decode.Group
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var avcPPSFormat decode.Group
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var avcSEIFormat decode.Group
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func init() {
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registry.MustRegister(decode.Format{
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Name: format.AVC_NALU,
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Description: "H.264/AVC Network Access Layer Unit",
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DecodeFn: avcNALUDecode,
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Dependencies: []decode.Dependency{
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{Names: []string{format.AVC_SPS}, Group: &avcSPSFormat},
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{Names: []string{format.AVC_PPS}, Group: &avcPPSFormat},
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{Names: []string{format.AVC_SEI}, Group: &avcSEIFormat},
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},
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})
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}
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// 14496-10 9.1 Parsing process for Exp-Golomb codes
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func expGolomb(d *decode.D) uint64 {
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leadingZeroBits := -1
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for b := false; !b; leadingZeroBits++ {
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b = d.Bool()
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}
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var expN uint64
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if leadingZeroBits == 0 {
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expN = 1
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} else {
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expN = 2 << (leadingZeroBits - 1)
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}
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return expN - 1 + d.U(leadingZeroBits)
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}
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func uEV(d *decode.D) uint64 { return expGolomb(d) }
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func sEV(d *decode.D) int64 {
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v := expGolomb(d) + 1
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return mathextra.ZigZag(v) - -int64(v&1)
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}
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const (
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avcNALCodedSliceNonIDR = 1
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avcNALCodedSlicePartitionA = 2
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avcNALCodedSlicePartitionB = 3
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avcNALCodedSlicePartitionC = 4
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avcNALCodedSliceIDR = 5
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avcNALSupplementalEnhancementInformation = 6
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avcNALSequenceParameterSet = 7
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avcNALPictureParameterSet = 8
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avcNALCodedSliceAuxWithoutPartition = 19
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avcNALCodedSliceExtension = 20
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)
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var avcNALNames = scalar.UToScalar{
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1: {Sym: "SLICE", Description: "Coded slice of a non-IDR picture"},
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2: {Sym: "DPA", Description: "Coded slice data partition A"},
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3: {Sym: "DPB", Description: "Coded slice data partition B"},
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4: {Sym: "DPC", Description: "Coded slice data partition C"},
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5: {Sym: "IDR_SLICE", Description: "Coded slice of an IDR picture"},
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avcNALSupplementalEnhancementInformation: {Sym: "SEI", Description: "Supplemental enhancement information"},
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avcNALSequenceParameterSet: {Sym: "SPS", Description: "Sequence parameter set"},
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avcNALPictureParameterSet: {Sym: "PPS", Description: "Picture parameter set"},
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9: {Sym: "AUD", Description: "Access unit delimiter"},
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10: {Sym: "EOSEQ", Description: "End of sequence"},
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11: {Sym: "EOS", Description: "End of stream"},
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12: {Sym: "FILLER", Description: "Filler data"},
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13: {Sym: "SPS_EXT", Description: "Sequence parameter set extension"},
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14: {Sym: "PREFIX", Description: "Prefix NAL unit"},
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15: {Sym: "SUB_SPS", Description: "Subset sequence parameter set"},
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19: {Sym: "AUX_SLICE", Description: "Coded slice of an auxiliary coded picture without partitioning"},
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20: {Sym: "EXTEN_SLICE", Description: "Coded slice extension"},
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}
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var sliceNames = scalar.UToSymStr{
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0: "P",
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1: "B",
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2: "I",
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3: "SP",
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4: "SI",
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5: "P",
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6: "B",
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7: "I",
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8: "SP",
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9: "SI",
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}
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func avcNALUDecode(d *decode.D, in interface{}) interface{} {
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d.FieldBool("forbidden_zero_bit")
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d.FieldU2("nal_ref_idc")
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nalType := d.FieldU5("nal_unit_type", avcNALNames)
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unescapedBb := d.MustNewBitBufFromReader(decode.NALUnescapeReader{Reader: d.BitBufRange(d.Pos(), d.BitsLeft())})
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switch nalType {
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case avcNALCodedSliceNonIDR,
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avcNALCodedSlicePartitionA,
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avcNALCodedSlicePartitionB,
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avcNALCodedSlicePartitionC,
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avcNALCodedSliceIDR,
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avcNALCodedSliceAuxWithoutPartition,
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avcNALCodedSliceExtension:
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d.FieldStruct("slice_header", func(d *decode.D) {
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d.FieldUFn("first_mb_in_slice", uEV)
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d.FieldUFn("slice_type", uEV, sliceNames)
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d.FieldUFn("pic_parameter_set_id", uEV)
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// TODO: if ( separate_colour_plane_flag from SPS ) colour_plane_id; frame_num
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})
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case avcNALSupplementalEnhancementInformation:
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d.FieldFormatBitBuf("sei", unescapedBb, avcSEIFormat, nil)
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case avcNALSequenceParameterSet:
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d.FieldFormatBitBuf("sps", unescapedBb, avcSPSFormat, nil)
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case avcNALPictureParameterSet:
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d.FieldFormatBitBuf("pps", unescapedBb, avcPPSFormat, nil)
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}
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d.FieldRawLen("data", d.BitsLeft())
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return nil
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}
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