pmt.go

// Copyright 2020, Chef.  All rights reserved.
// https://github.com/q191201771/lal
//
// Use of this source code is governed by a MIT-style license
// that can be found in the License file.
//
// Author: Chef (191201771@qq.com)

package mpegts

import (
	"github.com/q191201771/lal/pkg/base"
	"github.com/q191201771/naza/pkg/nazabits"
)

// Pmt
//
// ----------------------------------------
// Program Map Table
// <iso13818-1.pdf> <2.4.4.8> <page 64/174>
// table_id                 [8b]  *
// section_syntax_indicator [1b]
// 0                        [1b]
// reserved                 [2b]
// section_length           [12b] **
// program_number           [16b] **
// reserved                 [2b]
// version_number           [5b]
// current_next_indicator   [1b]  *
// section_number           [8b]  *
// last_section_number      [8b]  *
// reserved                 [3b]
// PCR_PID                  [13b] **
// reserved                 [4b]
// program_info_length      [12b] **
// -----loop-----
// stream_type              [8b]  *
// reserved                 [3b]
// elementary_PID           [13b] **
// reserved                 [4b]
// ES_info_length_length    [12b] **
// --------------
// CRC32                    [32b] ****
// ----------------------------------------
type Pmt struct {
	tid             uint8
	ssi             uint8
	sl              uint16
	pn              uint16
	vn              uint8
	cni             uint8
	sn              uint8
	lsn             uint8
	pp              uint16
	pil             uint16
	ProgramElements []PmtProgramElement
	crc32           uint32
}

type PmtProgramElement struct {
	StreamType  uint8
	Pid         uint16
	Length      uint16
	Descriptors []Descriptor
}

func ParsePmt(b []byte) (pmt Pmt) {
	br := nazabits.NewBitReader(b)
	pmt.tid, _ = br.ReadBits8(8)
	pmt.ssi, _ = br.ReadBits8(1)
	_, _ = br.ReadBits8(3)
	pmt.sl, _ = br.ReadBits16(12)
	length := pmt.sl - 13
	pmt.pn, _ = br.ReadBits16(16)
	_, _ = br.ReadBits8(2)
	pmt.vn, _ = br.ReadBits8(5)
	pmt.cni, _ = br.ReadBits8(1)
	pmt.sn, _ = br.ReadBits8(8)
	pmt.lsn, _ = br.ReadBits8(8)
	_, _ = br.ReadBits8(3)
	pmt.pp, _ = br.ReadBits16(13)
	_, _ = br.ReadBits8(4)
	pmt.pil, _ = br.ReadBits16(12)
	if pmt.pil != 0 {
		Log.Warn(pmt.pil)
		_, _ = br.ReadBytes(uint(pmt.pil))
	}

	for i := uint16(0); i < length; i += 5 {
		var ppe PmtProgramElement
		ppe.StreamType, _ = br.ReadBits8(8)
		_, _ = br.ReadBits8(3)
		ppe.Pid, _ = br.ReadBits16(13)
		_, _ = br.ReadBits8(4)
		ppe.Length, _ = br.ReadBits16(12)
		if ppe.Length != 0 {
			Log.Warn(ppe.Length)
			_, _ = br.ReadBits32(uint(ppe.Length))
		}
		pmt.ProgramElements = append(pmt.ProgramElements, ppe)
	}

	return
}

func (pmt *Pmt) SearchPid(pid uint16) *PmtProgramElement {
	for _, ppe := range pmt.ProgramElements {
		if ppe.Pid == pid {
			return &ppe
		}
	}
	return nil
}

func PackPmt(videoCodecId, audioCodecId int) []byte {
	ts := make([]byte, 188)
	tsheader := []byte{0x47, 0x50, 0x01, 0x10}
	copy(ts, tsheader)

	psi := NewPsi()
	psi.sectionData.header.tableId = TsPsiIdPms
	psi.sectionData.header.sectionSyntaxIndicator = 1
	psi.sectionData.section.tableIdExtension = 1
	psi.sectionData.section.currentNextIndicator = 1
	psi.sectionData.pmtData.pcrPid = 0x100

	videoStreamType := StreamTypeUnknown
	if videoCodecId == int(base.RtmpCodecIdAvc) {
		videoStreamType = StreamTypeAvc
	} else if videoCodecId == int(base.RtmpCodecIdHevc) {
		videoStreamType = StreamTypeHevc
	}

	if videoStreamType != StreamTypeUnknown {
		psi.sectionData.pmtData.pes = append(psi.sectionData.pmtData.pes, PmtProgramElement{
			StreamType: videoStreamType,
			Pid:        PidVideo,
		})
	}

	audioStreamType := StreamTypeUnknown
	if audioCodecId == int(base.RtmpSoundFormatAac) {
		audioStreamType = StreamTypeAac
	} else if audioCodecId == int(base.RtmpSoundFormatOpus) {
		audioStreamType = StreamTypePrivate
	}

	if audioStreamType != StreamTypeUnknown {
		pmtEle := PmtProgramElement{
			StreamType: audioStreamType,
			Pid:        PidAudio,
		}

		if audioCodecId == int(base.RtmpSoundFormatOpus) {
			descriptor := []Descriptor{
				{
					Length: 4,
					Tag:    DescriptorTagRegistration,
					Registration: DescriptorRegistration{
						FormatIdentifier: opusIdentifier,
					},
				},
				{
					Length: 2,
					Tag:    DescriptorTagExtension,
					Extension: DescriptorExtension{
						Tag:     0x80,
						Unknown: []uint8{0x02},
					},
				},
			}

			pmtEle.Descriptors = append(pmtEle.Descriptors, descriptor...)
		}

		psi.sectionData.pmtData.pes = append(psi.sectionData.pmtData.pes, pmtEle)
	}

	psilen, psiData := psi.Pack()
	copy(ts[4:], psiData)

	stuffinglen := 188 - 4 - psilen
	for i := 0; i < stuffinglen; i++ {
		ts[4+psilen+i] = 0xff
	}

	return ts
}