323 lines
8.9 KiB
Go
323 lines
8.9 KiB
Go
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package astits
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import (
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"fmt"
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"github.com/pkg/errors"
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)
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// P-STD buffer scales
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const (
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PSTDBufferScale128Bytes = 0
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PSTDBufferScale1024Bytes = 1
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)
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// PTS DTS indicator
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const (
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PTSDTSIndicatorBothPresent = 3
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PTSDTSIndicatorIsForbidden = 1
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PTSDTSIndicatorNoPTSOrDTS = 0
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PTSDTSIndicatorOnlyPTS = 2
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)
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// Stream IDs
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const (
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StreamIDPrivateStream1 = 189
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StreamIDPaddingStream = 190
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StreamIDPrivateStream2 = 191
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)
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// Trick mode controls
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const (
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TrickModeControlFastForward = 0
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TrickModeControlFastReverse = 3
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TrickModeControlFreezeFrame = 2
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TrickModeControlSlowMotion = 1
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TrickModeControlSlowReverse = 4
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)
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// PESData represents a PES data
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// https://en.wikipedia.org/wiki/Packetized_elementary_stream
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// http://dvd.sourceforge.net/dvdinfo/pes-hdr.html
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// http://happy.emu.id.au/lab/tut/dttb/dtbtut4b.htm
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type PESData struct {
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Data []byte
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Header *PESHeader
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}
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// PESHeader represents a packet PES header
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type PESHeader struct {
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OptionalHeader *PESOptionalHeader
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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.
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StreamID uint8 // Examples: Audio streams (0xC0-0xDF), Video streams (0xE0-0xEF)
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}
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// PESOptionalHeader represents a PES optional header
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type PESOptionalHeader struct {
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AdditionalCopyInfo uint8
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CRC uint16
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DataAlignmentIndicator bool // True indicates that the PES packet header is immediately followed by the video start code or audio syncword
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DSMTrickMode *DSMTrickMode
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DTS *ClockReference
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ESCR *ClockReference
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ESRate uint32
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Extension2Data []byte
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Extension2Length uint8
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HasAdditionalCopyInfo bool
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HasCRC bool
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HasDSMTrickMode bool
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HasESCR bool
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HasESRate bool
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HasExtension bool
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HasExtension2 bool
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HasOptionalFields bool
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HasPackHeaderField bool
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HasPrivateData bool
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HasProgramPacketSequenceCounter bool
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HasPSTDBuffer bool
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HeaderLength uint8
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IsCopyrighted bool
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IsOriginal bool
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MarkerBits uint8
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MPEG1OrMPEG2ID uint8
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OriginalStuffingLength uint8
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PacketSequenceCounter uint8
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PackField uint8
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Priority bool
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PrivateData []byte
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PSTDBufferScale uint8
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PSTDBufferSize uint16
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PTS *ClockReference
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PTSDTSIndicator uint8
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ScramblingControl uint8
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}
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// DSMTrickMode represents a DSM trick mode
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// 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
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type DSMTrickMode struct {
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FieldID uint8
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FrequencyTruncation uint8
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IntraSliceRefresh uint8
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RepeatControl uint8
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TrickModeControl uint8
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}
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// parsePESData parses a PES data
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func parsePESData(i []byte) (d *PESData, err error) {
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// Init
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d = &PESData{}
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// Parse header
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var offset, dataStart, dataEnd = 3, 0, 0
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if d.Header, dataStart, dataEnd, err = parsePESHeader(i, &offset); err != nil {
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err = errors.Wrap(err, "astits: parsing PES header failed")
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return
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}
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// Parse data
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d.Data = i[dataStart:dataEnd]
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return
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}
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// hasPESOptionalHeader checks whether the data has a PES optional header
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func hasPESOptionalHeader(streamID uint8) bool {
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return streamID != StreamIDPaddingStream && streamID != StreamIDPrivateStream2
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}
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// parsePESData parses a PES header
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func parsePESHeader(i []byte, offset *int) (h *PESHeader, dataStart, dataEnd int, err error) {
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// Init
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h = &PESHeader{}
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// Stream ID
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h.StreamID = uint8(i[*offset])
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*offset += 1
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// Length
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h.PacketLength = uint16(i[*offset])<<8 | uint16(i[*offset+1])
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*offset += 2
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// Data end
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if h.PacketLength > 0 {
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dataEnd = *offset + int(h.PacketLength)
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} else {
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dataEnd = len(i)
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}
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// Check for incomplete data
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if dataEnd > len(i) {
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err = fmt.Errorf("astits: pes dataEnd (%d) > len(i) (%d)", dataEnd, len(i))
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return
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}
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// Optional header
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if hasPESOptionalHeader(h.StreamID) {
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h.OptionalHeader, dataStart = parsePESOptionalHeader(i, offset)
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} else {
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dataStart = *offset
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}
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return
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}
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// parsePESOptionalHeader parses a PES optional header
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func parsePESOptionalHeader(i []byte, offset *int) (h *PESOptionalHeader, dataStart int) {
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// Init
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h = &PESOptionalHeader{}
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// Marker bits
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h.MarkerBits = uint8(i[*offset]) >> 6
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// Scrambling control
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h.ScramblingControl = uint8(i[*offset]) >> 4 & 0x3
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// Priority
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h.Priority = uint8(i[*offset])&0x8 > 0
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// Data alignment indicator
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h.DataAlignmentIndicator = uint8(i[*offset])&0x4 > 0
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// Copyrighted
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h.IsCopyrighted = uint(i[*offset])&0x2 > 0
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// Original or copy
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h.IsOriginal = uint8(i[*offset])&0x1 > 0
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*offset += 1
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// PTS DST indicator
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h.PTSDTSIndicator = uint8(i[*offset]) >> 6 & 0x3
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// Flags
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h.HasESCR = uint8(i[*offset])&0x20 > 0
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h.HasESRate = uint8(i[*offset])&0x10 > 0
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h.HasDSMTrickMode = uint8(i[*offset])&0x8 > 0
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h.HasAdditionalCopyInfo = uint8(i[*offset])&0x4 > 0
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h.HasCRC = uint8(i[*offset])&0x2 > 0
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h.HasExtension = uint8(i[*offset])&0x1 > 0
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*offset += 1
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// Header length
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h.HeaderLength = uint8(i[*offset])
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*offset += 1
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// Data start
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dataStart = *offset + int(h.HeaderLength)
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// PTS/DTS
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if h.PTSDTSIndicator == PTSDTSIndicatorOnlyPTS {
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h.PTS = parsePTSOrDTS(i[*offset:])
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*offset += 5
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} else if h.PTSDTSIndicator == PTSDTSIndicatorBothPresent {
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h.PTS = parsePTSOrDTS(i[*offset:])
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*offset += 5
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h.DTS = parsePTSOrDTS(i[*offset:])
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*offset += 5
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}
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// ESCR
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if h.HasESCR {
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h.ESCR = parseESCR(i[*offset:])
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*offset += 6
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}
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// ES rate
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if h.HasESRate {
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h.ESRate = uint32(i[*offset])&0x7f<<15 | uint32(i[*offset+1])<<7 | uint32(i[*offset+2])>>1
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*offset += 3
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}
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// Trick mode
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if h.HasDSMTrickMode {
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h.DSMTrickMode = parseDSMTrickMode(i[*offset])
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*offset += 1
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}
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// Additional copy info
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if h.HasAdditionalCopyInfo {
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h.AdditionalCopyInfo = i[*offset] & 0x7f
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*offset += 1
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}
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// CRC
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if h.HasCRC {
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h.CRC = uint16(i[*offset])>>8 | uint16(i[*offset+1])
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*offset += 2
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}
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// Extension
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if h.HasExtension {
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// Flags
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h.HasPrivateData = i[*offset]&0x80 > 0
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h.HasPackHeaderField = i[*offset]&0x40 > 0
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h.HasProgramPacketSequenceCounter = i[*offset]&0x20 > 0
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h.HasPSTDBuffer = i[*offset]&0x10 > 0
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h.HasExtension2 = i[*offset]&0x1 > 0
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*offset += 1
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// Private data
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if h.HasPrivateData {
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h.PrivateData = i[*offset : *offset+16]
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*offset += 16
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}
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// Pack field length
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if h.HasPackHeaderField {
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h.PackField = uint8(i[*offset])
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*offset += 1
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}
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// Program packet sequence counter
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if h.HasProgramPacketSequenceCounter {
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h.PacketSequenceCounter = uint8(i[*offset]) & 0x7f
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h.MPEG1OrMPEG2ID = uint8(i[*offset+1]) >> 6 & 0x1
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h.OriginalStuffingLength = uint8(i[*offset+1]) & 0x3f
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*offset += 2
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}
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// P-STD buffer
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if h.HasPSTDBuffer {
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h.PSTDBufferScale = i[*offset] >> 5 & 0x1
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h.PSTDBufferSize = uint16(i[*offset])&0x1f<<8 | uint16(i[*offset+1])
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*offset += 2
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}
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// Extension 2
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if h.HasExtension2 {
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// Length
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h.Extension2Length = uint8(i[*offset]) & 0x7f
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*offset += 2
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// Data
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h.Extension2Data = i[*offset : *offset+int(h.Extension2Length)]
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*offset += int(h.Extension2Length)
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}
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}
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return
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}
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// parseDSMTrickMode parses a DSM trick mode
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func parseDSMTrickMode(i byte) (m *DSMTrickMode) {
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m = &DSMTrickMode{}
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m.TrickModeControl = i >> 5
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if m.TrickModeControl == TrickModeControlFastForward || m.TrickModeControl == TrickModeControlFastReverse {
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m.FieldID = i >> 3 & 0x3
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m.IntraSliceRefresh = i >> 2 & 0x1
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m.FrequencyTruncation = i & 0x3
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} else if m.TrickModeControl == TrickModeControlFreezeFrame {
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m.FieldID = i >> 3 & 0x3
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} else if m.TrickModeControl == TrickModeControlSlowMotion || m.TrickModeControl == TrickModeControlSlowReverse {
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m.RepeatControl = i & 0x1f
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}
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return
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}
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// parsePTSOrDTS parses a PTS or a DTS
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func parsePTSOrDTS(i []byte) *ClockReference {
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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)
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}
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// parseESCR parses an ESCR
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func parseESCR(i []byte) *ClockReference {
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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
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return newClockReference(int(escr>>9), int(escr&0x1ff))
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}
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