mirror of https://bitbucket.org/ausocean/av.git
129 lines
5.3 KiB
Go
129 lines
5.3 KiB
Go
/*
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NAME
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pes.go -
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DESCRIPTION
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See Readme.md
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AUTHOR
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Saxon A. Nelson-Milton <saxon.milton@gmail.com>
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LICENSE
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pes.go is Copyright (C) 2017 the Australian Ocean Lab (AusOcean)
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It is free software: you can redistribute it and/or modify them
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under the terms of the GNU General Public License as published by the
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Free Software Foundation, either version 3 of the License, or (at your
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option) any later version.
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It is distributed in the hope that it will be useful, but WITHOUT
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ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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for more details.
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You should have received a copy of the GNU General Public License
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along with revid in gpl.txt. If not, see http://www.gnu.org/licenses.
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*/
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package pes
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import "github.com/Comcast/gots"
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const MaxPesSize = 64 * 1 << 10 // 65536
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/*
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The below data struct encapsulates the fields of an PES packet. Below is
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the formatting of a PES packet for reference!
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PES Packet Formatting
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============================================================================
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| octet no | bit 0 | bit 1 | bit 2 | bit 3 | bit 4 | bit 5 | bit 6 | bit 7 |
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============================================================================
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| octet 0 | 0x00 |
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----------------------------------------------------------------------------
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| octet 1 | 0x00 |
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----------------------------------------------------------------------------
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| octet 2 | 0x01 |
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----------------------------------------------------------------------------
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| octet 3 | Stream ID (0xE0 for video) |
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----------------------------------------------------------------------------
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| octet 4 | PES Packet Length (no of bytes in packet after this field) |
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----------------------------------------------------------------------------
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| octet 5 | PES Length cont. |
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----------------------------------------------------------------------------
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| octet 6 | 0x2 | SC | Prior | DAI | Copyr | Copy |
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----------------------------------------------------------------------------
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| octet 7 | PDI | ESCRF | ESRF | DSMTMF| ACIF | CRCF | EF |
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----------------------------------------------------------------------------
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| octet 8 | PES Header Length |
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----------------------------------------------------------------------------
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| optional | optional fields (determined by flags above) (variable Length) |
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----------------------------------------------------------------------------
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| - | ... |
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----------------------------------------------------------------------------
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| optional | stuffing bytes (varible length) |
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----------------------------------------------------------------------------
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| - | ... |
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----------------------------------------------------------------------------
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| Optional | Data (variable length) |
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----------------------------------------------------------------------------
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| - | ... |
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----------------------------------------------------------------------------
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*/
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// TODO: add DSMTM, ACI, CRC, Ext fields
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type Packet struct {
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StreamID byte // Type of stream
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Length uint16 // Pes packet length in bytes after this field
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SC byte // Scrambling control
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Priority bool // Priority Indicator
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DAI bool // Data alginment indicator
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Copyright bool // Copyright indicator
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Original bool // Original data indicator
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PDI byte // PTS DTS indicator
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ESCRF bool // Elementary stream clock reference flag
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ESRF bool // Elementary stream rate reference flag
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DSMTMF bool // Dsm trick mode flag
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ACIF bool // Additional copy info flag
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CRCF bool // Not sure
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EF bool // Extension flag
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HeaderLength byte // Pes header length
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PTS uint64 // Presentation time stamp
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DTS uint64 // Decoding timestamp
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ESCR uint64 // Elementary stream clock reference
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ESR uint32 // Elementary stream rate reference
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Stuff []byte // Stuffing bytes
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Data []byte // Pes packet data
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}
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func (p *Packet) Bytes(buf []byte) []byte {
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if buf == nil || cap(buf) != MaxPesSize {
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buf = make([]byte, 0, MaxPesSize)
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}
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buf = buf[:0]
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buf = append(buf, []byte{
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0x00, 0x00, 0x01,
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p.StreamID,
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byte((p.Length & 0xFF00) >> 8),
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byte(p.Length & 0x00FF),
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(0x2<<6 | p.SC<<4 | boolByte(p.Priority)<<3 | boolByte(p.DAI)<<2 |
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boolByte(p.Copyright)<<1 | boolByte(p.Original)),
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(p.PDI<<6 | boolByte(p.ESCRF)<<5 | boolByte(p.ESRF)<<4 | boolByte(p.DSMTMF)<<3 |
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boolByte(p.ACIF)<<2 | boolByte(p.CRCF)<<1 | boolByte(p.EF)),
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p.HeaderLength,
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}...)
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if p.PDI == byte(2) {
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ptsIdx := len(buf)
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buf = buf[:ptsIdx+5]
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gots.InsertPTS(buf[ptsIdx:], p.PTS)
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}
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buf = append(buf, append(p.Stuff, p.Data...)...)
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return buf
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}
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func boolByte(b bool) byte {
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if b {
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return 1
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}
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return 0
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}
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