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package mpeg
// TODO: unescape configurable? merge with AVC_NAL? merge with HEVC?
import (
"github.com/wader/fq/format"
"github.com/wader/fq/internal/mathex"
"github.com/wader/fq/pkg/bitio"
"github.com/wader/fq/pkg/decode"
"github.com/wader/fq/pkg/interp"
"github.com/wader/fq/pkg/scalar"
)
var avcSPSFormat decode.Group
var avcPPSFormat decode.Group
var avcSEIFormat decode.Group
func init() {
interp.RegisterFormat(
format.AVC_NALU,
&decode.Format{
Description: "H.264/AVC Network Access Layer Unit",
DecodeFn: avcNALUDecode,
Dependencies: []decode.Dependency{
{Groups: []*decode.Group{format.AVC_SPS}, Out: &avcSPSFormat},
{Groups: []*decode.Group{format.AVC_PPS}, Out: &avcPPSFormat},
{Groups: []*decode.Group{format.AVC_SEI}, Out: &avcSEIFormat},
},
})
}
// 14496-10 9.1 Parsing process for Exp-Golomb codes
func expGolomb(d *decode.D) uint64 {
leadingZeroBits := -1
for b := false; !b; leadingZeroBits++ {
b = d.Bool()
}
var expN uint64
if leadingZeroBits == 0 {
expN = 1
} else {
expN = 2 << (leadingZeroBits - 1)
}
return expN - 1 + d.U(leadingZeroBits)
}
func uEV(d *decode.D) uint64 { return expGolomb(d) }
func sEV(d *decode.D) int64 {
v := expGolomb(d) + 1
return mathex.ZigZag[uint64, int64](v) - -int64(v&1)
}
const (
avcNALCodedSliceNonIDR = 1
avcNALCodedSlicePartitionA = 2
avcNALCodedSlicePartitionB = 3
avcNALCodedSlicePartitionC = 4
avcNALCodedSliceIDR = 5
avcNALSupplementalEnhancementInformation = 6
avcNALSequenceParameterSet = 7
avcNALPictureParameterSet = 8
avcNALCodedSliceAuxWithoutPartition = 19
avcNALCodedSliceExtension = 20
)
var avcNALNames = scalar.UintMap{
1: {Sym: "slice", Description: "Coded slice of a non-IDR picture"},
2: {Sym: "dpa", Description: "Coded slice data partition A"},
3: {Sym: "dpb", Description: "Coded slice data partition B"},
4: {Sym: "dpc", Description: "Coded slice data partition C"},
5: {Sym: "idr_slice", Description: "Coded slice of an IDR picture"},
avcNALSupplementalEnhancementInformation: {Sym: "sei", Description: "Supplemental enhancement information"},
avcNALSequenceParameterSet: {Sym: "sps", Description: "Sequence parameter set"},
avcNALPictureParameterSet: {Sym: "pps", Description: "Picture parameter set"},
9: {Sym: "aud", Description: "Access unit delimiter"},
10: {Sym: "eoseq", Description: "End of sequence"},
11: {Sym: "eos", Description: "End of stream"},
12: {Sym: "filler", Description: "Filler data"},
13: {Sym: "sps_ext", Description: "Sequence parameter set extension"},
14: {Sym: "prefix", Description: "Prefix NAL unit"},
15: {Sym: "sub_sps", Description: "Subset sequence parameter set"},
19: {Sym: "aux_slice", Description: "Coded slice of an auxiliary coded picture without partitioning"},
20: {Sym: "exten_slice", Description: "Coded slice extension"},
}
var sliceNames = scalar.UintMapSymStr{
0: "p",
1: "b",
2: "i",
3: "sp",
4: "si",
5: "p",
6: "b",
7: "i",
8: "sp",
9: "si",
}
func avcNALUDecode(d *decode.D) any {
d.FieldBool("forbidden_zero_bit")
d.FieldU2("nal_ref_idc")
nalType := d.FieldU5("nal_unit_type", avcNALNames)
unescapedBR := d.NewBitBufFromReader(nalUnescapeReader{Reader: bitio.NewIOReader(d.BitBufRange(d.Pos(), d.BitsLeft()))})
switch nalType {
case avcNALCodedSliceNonIDR,
avcNALCodedSlicePartitionA,
avcNALCodedSlicePartitionB,
avcNALCodedSlicePartitionC,
avcNALCodedSliceIDR,
avcNALCodedSliceAuxWithoutPartition,
avcNALCodedSliceExtension:
d.FieldStruct("slice_header", func(d *decode.D) {
d.FieldUintFn("first_mb_in_slice", uEV)
d.FieldUintFn("slice_type", uEV, sliceNames)
d.FieldUintFn("pic_parameter_set_id", uEV)
// TODO: if ( separate_colour_plane_flag from SPS ) colour_plane_id; frame_num
})
case avcNALSupplementalEnhancementInformation:
d.FieldFormatBitBuf("sei", unescapedBR, &avcSEIFormat, nil)
case avcNALSequenceParameterSet:
d.FieldFormatBitBuf("sps", unescapedBR, &avcSPSFormat, nil)
case avcNALPictureParameterSet:
d.FieldFormatBitBuf("pps", unescapedBR, &avcPPSFormat, nil)
}
d.FieldRawLen("data", d.BitsLeft())
return nil
}
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