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87 lines
2.2 KiB
Go
87 lines
2.2 KiB
Go
// Copyright 2020, Chef. All rights reserved.
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// https://github.com/q191201771/lal
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//
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// Use of this source code is governed by a MIT-style license
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// that can be found in the License file.
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//
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// Author: Chef (191201771@qq.com)
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package mpegts
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import (
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"github.com/q191201771/naza/pkg/nazabits"
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)
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// -----------------------------------------------------------
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// <iso13818-1.pdf>
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// <2.4.3.6 PES packet> <page 49/174>
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// <Table E.1 - PES packet header example> <page 142/174>
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// <F.0.2 PES packet> <page 144/174>
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// packet_start_code_prefix [24b] *** always 0x00, 0x00, 0x01
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// stream_id [8b] *
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// PES_packet_length [16b] **
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// '10' [2b]
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// PES_scrambling_control [2b]
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// PES_priority [1b]
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// data_alignment_indicator [1b]
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// copyright [1b]
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// original_or_copy [1b] *
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// PTS_DTS_flags [2b]
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// ESCR_flag [1b]
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// ES_rate_flag [1b]
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// DSM_trick_mode_flag [1b]
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// additional_copy_info_flag [1b]
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// PES_CRC_flag [1b]
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// PES_extension_flag [1b] *
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// PES_header_data_length [8b] *
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// -----------------------------------------------------------
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type PES struct {
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pscp uint32
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sid uint8
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ppl uint16
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pad1 uint8
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ptsDtsFlag uint8
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pad2 uint8
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phdl uint8
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pts uint64
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dts uint64
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}
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func ParsePES(b []byte) (pes PES, length int) {
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br := nazabits.NewBitReader(b)
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pes.pscp, _ = br.ReadBits32(24)
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pes.sid, _ = br.ReadBits8(8)
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pes.ppl, _ = br.ReadBits16(16)
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pes.pad1, _ = br.ReadBits8(8)
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pes.ptsDtsFlag, _ = br.ReadBits8(2)
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pes.pad2, _ = br.ReadBits8(6)
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pes.phdl, _ = br.ReadBits8(8)
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_, _ = br.ReadBytes(uint(pes.phdl))
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length = 9 + int(pes.phdl)
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// 处理得不是特别标准
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if pes.ptsDtsFlag&0x2 != 0 {
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_, pes.pts = readPTS(b[9:])
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}
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if pes.ptsDtsFlag&0x1 != 0 {
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_, pes.dts = readPTS(b[14:])
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} else {
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pes.dts = pes.pts
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}
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//pes.pts = (pes.pts - delay) / 90
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//pes.dts = (pes.dts - delay) / 90
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return
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}
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// read pts or dts
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func readPTS(b []byte) (fb uint8, pts uint64) {
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fb = b[0] >> 4
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pts |= uint64((b[0]>>1)&0x07) << 30
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pts |= (uint64(b[1])<<8 | uint64(b[2])) >> 1 << 15
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pts |= (uint64(b[3])<<8 | uint64(b[4])) >> 1
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return
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}
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