mirror of https://bitbucket.org/ausocean/av.git
300 lines
7.2 KiB
Go
300 lines
7.2 KiB
Go
/*
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NAME
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psi.go
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DESCRIPTION
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See Readme.md
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AUTHOR
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Saxon Milton <saxon@ausocean.org>
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LICENSE
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psi.go is Copyright (C) 2018 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 psi
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// Lengths of section definitions
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const (
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ESSDDefLen = 5
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DescDefLen = 2
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PMTDefLen = 4
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PATLen = 4
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TSSDefLen = 5
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PSIDefLen = 3
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)
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// Table Type IDs
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const (
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PATTableID = 0x00
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PMTTableID = 0x02
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)
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// Consts relating to time description
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const (
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timeDescTag = 234
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timeTagIndx = 13
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timeDataIndx = 15
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timeDataSize = 8 // bytes, because time is stored in uint64
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)
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// Consts relating to location description
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const (
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locationDescTag = 235
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locationTagIndx = 23
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locationDataIndx = 25
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locationDataSize = 32 // bytes
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)
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// Program specific information
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type PSI struct {
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Pf byte // Point field
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Pfb []byte // Pointer filler bytes
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Tid byte // Table ID
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Ssi bool // Section syntax indicator (1 for PAT, PMT, CAT)
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Pb bool // Private bit (0 for PAT, PMT, CAT)
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Sl uint16 // Section length
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Tss *TSS // Table syntax section (length defined by SL) if length 0 then nil
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Crc uint32 // crc32 of entire table excluding pointer field, pointer filler bytes and the trailing CRC32
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}
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// Table syntax section
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type TSS struct {
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Tide uint16 // Table ID extension
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V byte // Version number
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Cni bool // Current/next indicator
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Sn byte // Section number
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Lsn byte // Last section number
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Sd SpecificData // Specific data PAT/PMT
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}
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// Specific Data, (could be PAT or PMT)
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type SpecificData interface {
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Bytes() []byte
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}
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// Program association table, implements SpecificData
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type PAT struct {
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Pn uint16 // Program Number
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Pmpid uint16 // Program map PID
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}
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// Program mapping table, implements SpecificData
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type PMT struct {
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Pcrpid uint16 // Program clock reference pid
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Pil uint16 // Program info length
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Pd []Desc // Program descriptors
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Essd *ESSD // Elementary stream specific data
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}
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// Elementary stream specific data
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type ESSD struct {
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St byte // Stream type
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Epid uint16 // Elementary pid
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Esil uint16 // Elementary stream
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Esd []Desc // Elementary stream desriptors
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}
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// Descriptor
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type Desc struct {
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Dt byte // Descriptor tag
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Dl byte // Descriptor length
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Dd []byte // Descriptor data
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}
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// ReadPSI creates a PSI data structure from a given byte slice that represents a PSI
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func ReadPSI(data []byte) *PSI {
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psi := PSI{}
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pos := 0
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psi.Pf = data[pos]
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if psi.Pf != 0 {
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panic("No support for pointer filler bytes")
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}
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psi.Tid = data[pos]
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pos++
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psi.Ssi = data[pos]&0x80 != 0
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psi.Pb = data[pos]&0x40 != 0
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psi.Sl = uint16(data[pos]&0x03)<<8 | uint16(data[pos+1])
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pos += 2
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psi.Tss = readTSS(data[pos:], &psi)
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return &psi
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}
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// ReadTSS creates a TSS data structure from a given byte slice that represents a TSS
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func readTSS(data []byte, p *PSI) *TSS {
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tss := TSS{}
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pos := 0
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tss.Tide = uint16(data[pos])<<8 | uint16(data[pos+1])
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pos += 2
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tss.V = (data[pos] & 0x3e) >> 1
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tss.Cni = data[pos]&0x01 != 0
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pos++
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tss.Sn = data[pos]
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pos++
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tss.Lsn = data[pos]
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pos++
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switch p.Tid {
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case PATTableID:
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tss.Sd = readPAT(data[pos:], &tss)
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case PMTTableID:
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tss.Sd = readPMT(data[pos:], &tss)
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default:
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panic("Can't yet deal with tables that are not PAT or PMT")
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}
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return &tss
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}
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// readPAT creates a pat struct based on a bytes slice representing a pat
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func readPAT(data []byte, p *TSS) *PAT {
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pat := PAT{}
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pos := 0
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pat.Pn = uint16(data[pos])<<8 | uint16(data[pos+1])
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pos += 2
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pat.Pmpid = uint16(data[pos]&0x1f)<<8 | uint16(data[pos+1])
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return &pat
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}
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// readPMT creates a pmt struct based on a bytes slice that represents a pmt
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func readPMT(data []byte, p *TSS) *PAT {
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pmt := PMT{}
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pos := 0
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pmt.Pcrpid = uint16(data[pos]&0x1f)<<8 | uint16(data[pos+1])
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pos += 2
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pmt.Pil = uint16(data[pos]&0x03)<<8 | uint16(data[pos+1])
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pos += 2
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if pmt.Pil != 0 {
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pmt.Pd = readDescs(data[pos:], int(pmt.Pil))
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}
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pos += int(pmt.Pil)
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// TODO Read ES stuff
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pmt.Essd = readEssd(data[pos:])
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return nil
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}
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// readDescs reads provides a slice of Descs given a byte slice that represents Descs
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// and the no of bytes that the descs accumilate
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func readDescs(data []byte, descLen int) (o []Desc) {
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pos := 0
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o = make([]Desc, 1)
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o[0].Dt = data[pos]
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pos++
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o[0].Dl = data[pos]
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pos++
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o[0].Dd = make([]byte, o[0].Dl)
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for i := 0; i < int(o[0].Dl); i++ {
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o[0].Dd[i] = data[pos]
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pos++
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}
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if 2+len(o[0].Dd) != descLen {
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panic("No support for reading more than one descriptor")
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}
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return
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}
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// readEESD creates an ESSD struct based on a bytes slice that represents ESSD
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func readEssd(data []byte) *ESSD {
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essd := ESSD{}
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pos := 0
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essd.St = data[pos]
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pos++
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essd.Epid = uint16(data[pos]&0x1f)<<8 | uint16(data[pos+1])
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pos += 2
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essd.Esil = uint16(data[pos]&0x03)<<8 | uint16(data[pos+1])
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pos += 2
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essd.Esd = readDescs(data[pos:], int(essd.Esil))
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return &essd
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}
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// Bytes outputs a byte slice representation of the PSI
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func (p *PSI) Bytes() []byte {
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out := make([]byte, 4)
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out[0] = p.Pf
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if p.Pf != 0 {
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panic("No support for pointer filler bytes")
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}
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out[1] = p.Tid
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out[2] = 0x80 | 0x30 | (0x03 & byte(p.Sl>>8))
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out[3] = byte(p.Sl)
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out = append(out, p.Tss.Bytes()...)
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out = addCrc(out)
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return out
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}
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// Bytes outputs a byte slice representation of the TSS
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func (t *TSS) Bytes() []byte {
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out := make([]byte, TSSDefLen)
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out[0] = byte(t.Tide >> 8)
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out[1] = byte(t.Tide)
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out[2] = 0xc0 | (0x3e & (t.V << 1)) | (0x01 & asByte(t.Cni))
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out[3] = t.Sn
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out[4] = t.Lsn
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out = append(out, t.Sd.Bytes()...)
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return out
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}
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// Bytes outputs a byte slice representation of the PAT
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func (p *PAT) Bytes() []byte {
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out := make([]byte, PATLen)
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out[0] = byte(p.Pn >> 8)
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out[1] = byte(p.Pn)
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out[2] = 0xe0 | (0x1f & byte(p.Pmpid>>8))
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out[3] = byte(p.Pmpid)
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return out
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}
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// Bytes outputs a byte slice representation of the PMT
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func (p *PMT) Bytes() []byte {
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out := make([]byte, PMTDefLen)
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out[0] = 0xe0 | (0x1f & byte(p.Pcrpid>>8)) // byte 10
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out[1] = byte(p.Pcrpid)
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out[2] = 0xf0 | (0x03 & byte(p.Pil>>8))
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out[3] = byte(p.Pil)
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for _, d := range p.Pd {
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out = append(out, d.Bytes()...)
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}
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out = append(out, p.Essd.Bytes()...)
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return out
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}
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// Bytes outputs a byte slice representation of the Desc
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func (d *Desc) Bytes() []byte {
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out := make([]byte, DescDefLen)
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out[0] = d.Dt
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out[1] = d.Dl
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out = append(out, d.Dd...)
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return out
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}
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// Bytes outputs a byte slice representation of the ESSD
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func (e *ESSD) Bytes() []byte {
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out := make([]byte, ESSDDefLen)
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out[0] = e.St
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out[1] = 0xe0 | (0x1f & byte(e.Epid>>8))
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out[2] = byte(e.Epid)
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out[3] = 0xf0 | (0x03 & byte(e.Esil>>8))
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out[4] = byte(e.Esil)
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for _, d := range e.Esd {
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out = append(out, d.Bytes()...)
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}
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return out
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}
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func asByte(b bool) (o byte) {
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if b {
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o = 0x01
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}
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return
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}
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