Add MP4 atoms reader

pkg/iso/reader.go

@@ -0,0 +1,99 @@
+package iso
+
+import (
+	"encoding/binary"
+	"io"
+
+	"github.com/AlexxIT/go2rtc/pkg/bits"
+)
+
+type Atom struct {
+	Name string
+	Data []byte
+
+	DecodeTime uint64
+
+	SamplesDuration []uint32
+	SamplesSize     []uint32
+}
+
+func DecodeAtoms(b []byte) ([]*Atom, error) {
+	var atoms []*Atom
+	for len(b) > 8 {
+		size := binary.BigEndian.Uint32(b)
+		if uint32(len(b)) < size {
+			return nil, io.EOF
+		}
+
+		name := string(b[4:8])
+		data := b[8:size]
+
+		b = b[size:]
+
+		switch name {
+		case Moof, MoofTraf:
+			childs, err := DecodeAtoms(data)
+			if err != nil {
+				return nil, err
+			}
+
+			atoms = append(atoms, childs...)
+
+		case MoofMfhd, MoofTrafTfhd:
+			continue
+
+		case MoofTrafTfdt:
+			if len(data) < 8 {
+				return nil, io.EOF
+			}
+
+			dt := binary.BigEndian.Uint64(data[4:])
+			atoms = append(atoms, &Atom{Name: name, DecodeTime: dt})
+
+		case MoofTrafTrun:
+			rd := bits.NewReader(data)
+
+			_ = rd.ReadByte() // version
+			flags := rd.ReadUint24()
+			samples := rd.ReadUint32()
+
+			if flags&TrunDataOffset != 0 {
+				_ = rd.ReadUint32() // skip
+			}
+			if flags&TrunFirstSampleFlags != 0 {
+				_ = rd.ReadUint32() // skip
+			}
+
+			atom := &Atom{Name: name}
+
+			for i := uint32(0); i < samples; i++ {
+				if flags&TrunSampleDuration != 0 {
+					atom.SamplesDuration = append(atom.SamplesDuration, rd.ReadUint32())
+				}
+				if flags&TrunSampleSize != 0 {
+					atom.SamplesSize = append(atom.SamplesSize, rd.ReadUint32())
+				}
+				if flags&TrunSampleFlags != 0 {
+					_ = rd.ReadUint32() // skip
+				}
+				if flags&TrunSampleCTS != 0 {
+					_ = rd.ReadUint32() // skip
+				}
+			}
+
+			if rd.EOF {
+				return nil, io.EOF
+			}
+
+			atoms = append(atoms, atom)
+
+		case Mdat:
+			atoms = append(atoms, &Atom{Name: name, Data: data})
+
+		default:
+			println("iso: unsupported atom: " + name)
+		}
+	}
+
+	return atoms, nil
+}