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samplegroupentries.go
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/
samplegroupentries.go
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package mp4
import (
"encoding/hex"
"fmt"
"io"
)
// SampleGroupEntry - like a box, but size and type are not in a header
type SampleGroupEntry interface {
// GroupingType SampleGroupEntry (uint32 according to spec)
Type() string // actually
// Size of SampleGroup Entry
Size() uint64
// Encode SampleGroupEntry to SliceWriter
Encode(sw *SliceWriter)
// Info - description of content.
Info(w io.Writer, specificBoxLevels, indent, indentStep string) (err error)
}
// SampleGroupEntryDecoder is function signature of the SampleGroupEntry Decode method
type SampleGroupEntryDecoder func(name string, length uint32, sr *SliceReader) (SampleGroupEntry, error)
var sgeDecoders map[string]SampleGroupEntryDecoder
func init() {
sgeDecoders = map[string]SampleGroupEntryDecoder{
"seig": DecodeSeigSampleGroupEntry,
"roll": DecodeRollSampleGroupEntry,
"rap ": DecodeRapSampleGroupEntry,
"alst": DecodeAlstSampleGroupEntry,
}
}
func decodeSampleGroupEntry(name string, length uint32, sr *SliceReader) (SampleGroupEntry, error) {
decode, ok := sgeDecoders[name]
if ok {
return decode(name, length, sr)
}
return DecodeUnknownSampleGroupEntry(name, length, sr)
}
// SeigSampleGroupEntry - CencSampleEncryptionInformationGroupEntry as defined in
// CEF ISO/IEC 23001-7 3rd edition 2016
type SeigSampleGroupEntry struct {
CryptByteBlock byte
SkipByteBlock byte
IsProtected byte
PerSampleIVSize byte
KID UUID
// ConstantIVSize byte given by len(ConstantIV)
ConstantIV []byte
}
// DecodeSeigSampleGroupEntry - decode Commone Encryption Sample Group Entry
func DecodeSeigSampleGroupEntry(name string, length uint32, sr *SliceReader) (SampleGroupEntry, error) {
s := &SeigSampleGroupEntry{}
_ = sr.ReadUint8() // Reserved
byteTwo := sr.ReadUint8()
s.CryptByteBlock = byteTwo >> 4
s.SkipByteBlock = byteTwo % 0xf
s.IsProtected = sr.ReadUint8()
s.PerSampleIVSize = sr.ReadUint8()
s.KID = UUID(sr.ReadBytes(16))
if s.IsProtected == 1 && s.PerSampleIVSize == 0 {
constantIVSize := int(sr.ReadUint8())
s.ConstantIV = sr.ReadBytes(constantIVSize)
}
if length != uint32(s.Size()) {
return nil, fmt.Errorf("seig: given length %d different from calculated size %d", length, s.Size())
}
return s, nil
}
func (s *SeigSampleGroupEntry) Type() string {
return "seig"
}
func (s *SeigSampleGroupEntry) Size() uint64 {
// reserved: 1
// cryptByteBlock + SkipByteBlock : 1
// isProtected: 1
// perSampleIVSize: 1
// KID: 16
size := 20
if s.IsProtected == 1 && s.PerSampleIVSize == 0 {
size += 1 + len(s.ConstantIV)
}
return uint64(size)
}
func (s *SeigSampleGroupEntry) Encode(sw *SliceWriter) {
sw.WriteUint8(0) // Reserved
byteTwo := s.CryptByteBlock<<4 | s.SkipByteBlock
sw.WriteUint8(byteTwo)
sw.WriteUint8(s.IsProtected)
sw.WriteUint8(s.PerSampleIVSize)
sw.WriteBytes(s.KID)
if s.IsProtected == 1 && s.PerSampleIVSize == 0 {
sw.WriteUint8(byte(len(s.ConstantIV)))
sw.WriteBytes(s.ConstantIV)
}
}
// Info - write box info to w
func (s *SeigSampleGroupEntry) Info(w io.Writer, specificBoxLevels, indent, indentStep string) (err error) {
bd := newInfoDumper(w, indent, s, -2, 0)
bd.write(" * cryptByteBlock: %d", s.CryptByteBlock)
bd.write(" * skipByteBlock: %d", s.SkipByteBlock)
bd.write(" * isProtected: %d", s.IsProtected)
bd.write(" * perSampleIVSize: %d", s.PerSampleIVSize)
bd.write(" * KID: %s", s.KID)
if s.IsProtected == 1 && s.PerSampleIVSize == 0 {
bd.write(" * constantIV: %s", hex.EncodeToString(s.ConstantIV))
}
return bd.err
}
// Unknown or not implemented SampleGroupEntry
type UnknownSampleGroupEntry struct {
Name string
Length uint32
Data []byte
}
func DecodeUnknownSampleGroupEntry(name string, length uint32, sr *SliceReader) (SampleGroupEntry, error) {
return &UnknownSampleGroupEntry{
Name: name,
Data: sr.ReadBytes(int(length)),
}, nil
}
func (s *UnknownSampleGroupEntry) Type() string {
return s.Name
}
func (s *UnknownSampleGroupEntry) Size() uint64 {
return uint64(len(s.Data))
}
func (s *UnknownSampleGroupEntry) Encode(sw *SliceWriter) {
sw.WriteBytes(s.Data)
}
// Info - write box info to w
func (s *UnknownSampleGroupEntry) Info(w io.Writer, specificBoxLevels, indent, indentStep string) (err error) {
bd := newInfoDumper(w, indent, s, -2, 0)
bd.write(" * Unknown data of length: %d", len(s.Data))
level := getInfoLevel(s, specificBoxLevels)
if level > 0 {
bd.write(" * data: %s", hex.EncodeToString(s.Data))
}
return bd.err
}
// RollSampleGroupEntry - Gradual Decoding Refresh "roll"
//
// ISO/IEC 14496-12 Ed. 6 2020 Section 10.1
//
// VisualRollRecoveryEntry / AudioRollRecoveryEntry / AudioPreRollEntry
type RollSampleGroupEntry struct {
RollDistance int16
}
func DecodeRollSampleGroupEntry(name string, length uint32, sr *SliceReader) (SampleGroupEntry, error) {
entry := &RollSampleGroupEntry{}
entry.RollDistance = sr.ReadInt16()
return entry, nil
}
func (s *RollSampleGroupEntry) Type() string {
return "roll"
}
func (s *RollSampleGroupEntry) Size() uint64 {
return 2
}
func (s *RollSampleGroupEntry) Encode(sw *SliceWriter) {
sw.WriteInt16(s.RollDistance)
}
// Info - write box info to w
func (s *RollSampleGroupEntry) Info(w io.Writer, specificBoxLevels, indent, indentStep string) (err error) {
bd := newInfoDumper(w, indent, s, -2, 0)
bd.write(" * rollDistance: %d", s.RollDistance)
return bd.err
}
// RapSampleGroupEntry - Random Access Point "rap "
//
// ISO/IEC 14496-12 Ed. 6 2020 Section 10.4 - VisualRandomAccessEntry
type RapSampleGroupEntry struct {
NumLeadingSamplesKnown uint8
NumLeadingSamples uint8
}
func DecodeRapSampleGroupEntry(name string, length uint32, sr *SliceReader) (SampleGroupEntry, error) {
entry := &RapSampleGroupEntry{}
byt := sr.ReadUint8()
entry.NumLeadingSamplesKnown = byt >> 7
entry.NumLeadingSamples = byt & 0x7F
return entry, nil
}
func (s *RapSampleGroupEntry) Type() string {
return "rap "
}
func (s *RapSampleGroupEntry) Size() uint64 {
return 1
}
func (s *RapSampleGroupEntry) Encode(sw *SliceWriter) {
var byt uint8
byt |= (s.NumLeadingSamplesKnown << 7)
byt |= (s.NumLeadingSamples)
sw.WriteUint8(byt)
}
// Info - write box info to w
func (s *RapSampleGroupEntry) Info(w io.Writer, specificBoxLevels, indent, indentStep string) (err error) {
bd := newInfoDumper(w, indent, s, -2, 0)
bd.write(" * numLeadingSamplesKnown: %d", s.NumLeadingSamplesKnown)
bd.write(" * numLeadingSamples: %d", s.NumLeadingSamples)
return bd.err
}
// AlstSampleGroupEntry - Alternative Startup Entry "alst"
//
// ISO/IEC 14496-12 Ed. 6 2020 Section 10.3 - AlternativeStartupEntry
type AlstSampleGroupEntry struct {
RollCount uint16
FirstOutputSample uint16
SampleOffset []uint32
NumOutputSamples []uint16
NumTotalSamples []uint16
}
func (s *AlstSampleGroupEntry) Type() string {
return "alst "
}
func (s *AlstSampleGroupEntry) Size() uint64 {
// RollCount: 2
// FirstOutputSample: 2
// SampleOffset: 4 * count
// NumOutputSamples: 2 * count
// NumTotalSamples: 2 * count
return uint64(4 + 4*len(s.SampleOffset) + 2*len(s.NumOutputSamples) + 2*len(s.NumTotalSamples))
}
func DecodeAlstSampleGroupEntry(name string, length uint32, sr *SliceReader) (SampleGroupEntry, error) {
entry := &AlstSampleGroupEntry{}
entry.RollCount = sr.ReadUint16()
entry.FirstOutputSample = sr.ReadUint16()
entry.SampleOffset = make([]uint32, int(entry.RollCount))
for i := 0; i < int(entry.RollCount); i++ {
entry.SampleOffset[i] = sr.ReadUint32()
}
remaining := int(length-uint32(entry.Size())) / 4
if remaining <= 0 {
return entry, nil
}
// Optional
entry.NumOutputSamples = make([]uint16, remaining)
entry.NumTotalSamples = make([]uint16, remaining)
for i := 0; i < remaining; i++ {
entry.NumOutputSamples[i] = sr.ReadUint16()
entry.NumTotalSamples[i] = sr.ReadUint16()
}
return entry, nil
}
func (s *AlstSampleGroupEntry) Encode(sw *SliceWriter) {
sw.WriteUint16(s.RollCount)
sw.WriteUint16(s.FirstOutputSample)
for _, offset := range s.SampleOffset {
sw.WriteUint32(offset)
}
for i := range s.NumOutputSamples {
sw.WriteUint16(s.NumOutputSamples[i])
sw.WriteUint16(s.NumTotalSamples[i])
}
}
// Info - write box info to w
func (s *AlstSampleGroupEntry) Info(w io.Writer, specificBoxLevels, indent, indentStep string) (err error) {
bd := newInfoDumper(w, indent, s, -2, 0)
bd.write(" * rollDistance: %d", s.RollCount)
bd.write(" * firstOutputSample: %d", s.FirstOutputSample)
level := getInfoLevel(s, specificBoxLevels)
if level > 0 {
for i, offset := range s.SampleOffset {
bd.write(" * sampleOffset[%d]: %d", i+1, offset)
}
for i := range s.NumOutputSamples {
bd.write(" * numOutputSamples[%d]: %d", i+1, s.NumOutputSamples[i])
bd.write(" * numTotalSamples[%d]: %d", i+1, s.NumTotalSamples[i])
}
}
return bd.err
}