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data_pes.go
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data_pes.go
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package astits
import (
"fmt"
"github.com/pkg/errors"
)
// P-STD buffer scales
const (
PSTDBufferScale128Bytes = 0
PSTDBufferScale1024Bytes = 1
)
// PTS DTS indicator
const (
PTSDTSIndicatorBothPresent = 3
PTSDTSIndicatorIsForbidden = 1
PTSDTSIndicatorNoPTSOrDTS = 0
PTSDTSIndicatorOnlyPTS = 2
)
// Stream IDs
const (
StreamIDPrivateStream1 = 189
StreamIDPaddingStream = 190
StreamIDPrivateStream2 = 191
)
// Trick mode controls
const (
TrickModeControlFastForward = 0
TrickModeControlFastReverse = 3
TrickModeControlFreezeFrame = 2
TrickModeControlSlowMotion = 1
TrickModeControlSlowReverse = 4
)
// PESData represents a PES data
// https://en.wikipedia.org/wiki/Packetized_elementary_stream
// http://dvd.sourceforge.net/dvdinfo/pes-hdr.html
// http://happy.emu.id.au/lab/tut/dttb/dtbtut4b.htm
type PESData struct {
Data []byte
Header *PESHeader
}
// PESHeader represents a packet PES header
type PESHeader struct {
OptionalHeader *PESOptionalHeader
PacketLength uint16 // Specifies the number of bytes remaining in the packet after this field. Can be zero. If the PES packet length is set to zero, the PES packet can be of any length. A value of zero for the PES packet length can be used only when the PES packet payload is a video elementary stream.
StreamID uint8 // Examples: Audio streams (0xC0-0xDF), Video streams (0xE0-0xEF)
}
// PESOptionalHeader represents a PES optional header
type PESOptionalHeader struct {
AdditionalCopyInfo uint8
CRC uint16
DataAlignmentIndicator bool // True indicates that the PES packet header is immediately followed by the video start code or audio syncword
DSMTrickMode *DSMTrickMode
DTS *ClockReference
ESCR *ClockReference
ESRate uint32
Extension2Data []byte
Extension2Length uint8
HasAdditionalCopyInfo bool
HasCRC bool
HasDSMTrickMode bool
HasESCR bool
HasESRate bool
HasExtension bool
HasExtension2 bool
HasOptionalFields bool
HasPackHeaderField bool
HasPrivateData bool
HasProgramPacketSequenceCounter bool
HasPSTDBuffer bool
HeaderLength uint8
IsCopyrighted bool
IsOriginal bool
MarkerBits uint8
MPEG1OrMPEG2ID uint8
OriginalStuffingLength uint8
PacketSequenceCounter uint8
PackField uint8
Priority bool
PrivateData []byte
PSTDBufferScale uint8
PSTDBufferSize uint16
PTS *ClockReference
PTSDTSIndicator uint8
ScramblingControl uint8
}
// DSMTrickMode represents a DSM trick mode
// https://books.google.fr/books?id=vwUrAwAAQBAJ&pg=PT501&lpg=PT501&dq=dsm+trick+mode+control&source=bl&ots=fI-9IHXMRL&sig=PWnhxrsoMWNQcl1rMCPmJGNO9Ds&hl=fr&sa=X&ved=0ahUKEwjogafD8bjXAhVQ3KQKHeHKD5oQ6AEINDAB#v=onepage&q=dsm%20trick%20mode%20control&f=false
type DSMTrickMode struct {
FieldID uint8
FrequencyTruncation uint8
IntraSliceRefresh uint8
RepeatControl uint8
TrickModeControl uint8
}
// parsePESData parses a PES data
func parsePESData(i []byte) (d *PESData, err error) {
// Init
d = &PESData{}
// Parse header
var offset, dataStart, dataEnd = 3, 0, 0
if d.Header, dataStart, dataEnd, err = parsePESHeader(i, &offset); err != nil {
err = errors.Wrap(err, "astits: parsing PES header failed")
return
}
// Parse data
d.Data = i[dataStart:dataEnd]
return
}
// hasPESOptionalHeader checks whether the data has a PES optional header
func hasPESOptionalHeader(streamID uint8) bool {
return streamID != StreamIDPaddingStream && streamID != StreamIDPrivateStream2
}
// parsePESData parses a PES header
func parsePESHeader(i []byte, offset *int) (h *PESHeader, dataStart, dataEnd int, err error) {
// Init
h = &PESHeader{}
// Stream ID
h.StreamID = uint8(i[*offset])
*offset += 1
// Length
h.PacketLength = uint16(i[*offset])<<8 | uint16(i[*offset+1])
*offset += 2
// Data end
if h.PacketLength > 0 {
dataEnd = *offset + int(h.PacketLength)
} else {
dataEnd = len(i)
}
// Check for incomplete data
if dataEnd > len(i) {
err = fmt.Errorf("astits: pes dataEnd (%d) > len(i) (%d)", dataEnd, len(i))
return
}
// Optional header
if hasPESOptionalHeader(h.StreamID) {
h.OptionalHeader, dataStart = parsePESOptionalHeader(i, offset)
} else {
dataStart = *offset
}
return
}
// parsePESOptionalHeader parses a PES optional header
func parsePESOptionalHeader(i []byte, offset *int) (h *PESOptionalHeader, dataStart int) {
// Init
h = &PESOptionalHeader{}
// Marker bits
h.MarkerBits = uint8(i[*offset]) >> 6
// Scrambling control
h.ScramblingControl = uint8(i[*offset]) >> 4 & 0x3
// Priority
h.Priority = uint8(i[*offset])&0x8 > 0
// Data alignment indicator
h.DataAlignmentIndicator = uint8(i[*offset])&0x4 > 0
// Copyrighted
h.IsCopyrighted = uint(i[*offset])&0x2 > 0
// Original or copy
h.IsOriginal = uint8(i[*offset])&0x1 > 0
*offset += 1
// PTS DST indicator
h.PTSDTSIndicator = uint8(i[*offset]) >> 6 & 0x3
// Flags
h.HasESCR = uint8(i[*offset])&0x20 > 0
h.HasESRate = uint8(i[*offset])&0x10 > 0
h.HasDSMTrickMode = uint8(i[*offset])&0x8 > 0
h.HasAdditionalCopyInfo = uint8(i[*offset])&0x4 > 0
h.HasCRC = uint8(i[*offset])&0x2 > 0
h.HasExtension = uint8(i[*offset])&0x1 > 0
*offset += 1
// Header length
h.HeaderLength = uint8(i[*offset])
*offset += 1
// Data start
dataStart = *offset + int(h.HeaderLength)
// PTS/DTS
if h.PTSDTSIndicator == PTSDTSIndicatorOnlyPTS {
h.PTS = parsePTSOrDTS(i[*offset:])
*offset += 5
} else if h.PTSDTSIndicator == PTSDTSIndicatorBothPresent {
h.PTS = parsePTSOrDTS(i[*offset:])
*offset += 5
h.DTS = parsePTSOrDTS(i[*offset:])
*offset += 5
}
// ESCR
if h.HasESCR {
h.ESCR = parseESCR(i[*offset:])
*offset += 6
}
// ES rate
if h.HasESRate {
h.ESRate = uint32(i[*offset])&0x7f<<15 | uint32(i[*offset+1])<<7 | uint32(i[*offset+2])>>1
*offset += 3
}
// Trick mode
if h.HasDSMTrickMode {
h.DSMTrickMode = parseDSMTrickMode(i[*offset])
*offset += 1
}
// Additional copy info
if h.HasAdditionalCopyInfo {
h.AdditionalCopyInfo = i[*offset] & 0x7f
*offset += 1
}
// CRC
if h.HasCRC {
h.CRC = uint16(i[*offset])>>8 | uint16(i[*offset+1])
*offset += 2
}
// Extension
if h.HasExtension {
// Flags
h.HasPrivateData = i[*offset]&0x80 > 0
h.HasPackHeaderField = i[*offset]&0x40 > 0
h.HasProgramPacketSequenceCounter = i[*offset]&0x20 > 0
h.HasPSTDBuffer = i[*offset]&0x10 > 0
h.HasExtension2 = i[*offset]&0x1 > 0
*offset += 1
// Private data
if h.HasPrivateData {
h.PrivateData = i[*offset : *offset+16]
*offset += 16
}
// Pack field length
if h.HasPackHeaderField {
h.PackField = uint8(i[*offset])
*offset += 1
}
// Program packet sequence counter
if h.HasProgramPacketSequenceCounter {
h.PacketSequenceCounter = uint8(i[*offset]) & 0x7f
h.MPEG1OrMPEG2ID = uint8(i[*offset+1]) >> 6 & 0x1
h.OriginalStuffingLength = uint8(i[*offset+1]) & 0x3f
*offset += 2
}
// P-STD buffer
if h.HasPSTDBuffer {
h.PSTDBufferScale = i[*offset] >> 5 & 0x1
h.PSTDBufferSize = uint16(i[*offset])&0x1f<<8 | uint16(i[*offset+1])
*offset += 2
}
// Extension 2
if h.HasExtension2 {
// Length
h.Extension2Length = uint8(i[*offset]) & 0x7f
*offset += 2
// Data
h.Extension2Data = i[*offset : *offset+int(h.Extension2Length)]
*offset += int(h.Extension2Length)
}
}
return
}
// parseDSMTrickMode parses a DSM trick mode
func parseDSMTrickMode(i byte) (m *DSMTrickMode) {
m = &DSMTrickMode{}
m.TrickModeControl = i >> 5
if m.TrickModeControl == TrickModeControlFastForward || m.TrickModeControl == TrickModeControlFastReverse {
m.FieldID = i >> 3 & 0x3
m.IntraSliceRefresh = i >> 2 & 0x1
m.FrequencyTruncation = i & 0x3
} else if m.TrickModeControl == TrickModeControlFreezeFrame {
m.FieldID = i >> 3 & 0x3
} else if m.TrickModeControl == TrickModeControlSlowMotion || m.TrickModeControl == TrickModeControlSlowReverse {
m.RepeatControl = i & 0x1f
}
return
}
// parsePTSOrDTS parses a PTS or a DTS
func parsePTSOrDTS(i []byte) *ClockReference {
return newClockReference(int(uint64(i[0])>>1&0x7<<30|uint64(i[1])<<22|uint64(i[2])>>1&0x7f<<15|uint64(i[3])<<7|uint64(i[4])>>1&0x7f), 0)
}
// parseESCR parses an ESCR
func parseESCR(i []byte) *ClockReference {
var escr = uint64(i[0])>>3&0x7<<39 | uint64(i[0])&0x3<<37 | uint64(i[1])<<29 | uint64(i[2])>>3<<24 | uint64(i[2])&0x3<<22 | uint64(i[3])<<14 | uint64(i[4])>>3<<9 | uint64(i[4])&0x3<<7 | uint64(i[5])>>1
return newClockReference(int(escr>>9), int(escr&0x1ff))
}