mirror of
https://github.com/cnotch/ipchub.git
synced 2025-09-26 19:41:18 +08:00
127 lines
3.5 KiB
Go
127 lines
3.5 KiB
Go
// Copyright (c) 2019,CAOHONGJU All rights reserved.
|
||
// Use of this source code is governed by a MIT-style
|
||
// license that can be found in the LICENSE file.
|
||
|
||
package rtp
|
||
|
||
import (
|
||
"fmt"
|
||
|
||
"github.com/cnotch/tomatox/av/aac"
|
||
)
|
||
|
||
type mpesFrameExtractor struct {
|
||
w FrameWriter
|
||
sizeLength int
|
||
indexLength int
|
||
extractFunc func(packet *Packet) error
|
||
}
|
||
|
||
// NewMPESFrameExtractor 实例化 MPES 帧提取器
|
||
func NewMPESFrameExtractor(w FrameWriter, sizeLength, indexLength int) FrameExtractor {
|
||
fe := &mpesFrameExtractor{
|
||
w: w,
|
||
sizeLength: sizeLength,
|
||
indexLength: indexLength,
|
||
}
|
||
switch sizeLength + indexLength {
|
||
case 8:
|
||
fe.extractFunc = fe.extractFor1ByteAUHeader
|
||
case 16:
|
||
fe.extractFunc = fe.extractFor2ByteAUHeader
|
||
default:
|
||
panic(fmt.Sprintf("not supported au_header size(%d,%d)", sizeLength, indexLength))
|
||
}
|
||
return fe
|
||
}
|
||
|
||
// 以下是当 sizelength=13;indexlength=3;indexdeltalength=3 时
|
||
// Au-header = 13+3 bits(2byte) 的示意图
|
||
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
|
||
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|
||
// | AU-headers-length |
|
||
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|
||
// | AU-header(1) |
|
||
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|
||
// | AU-header(2) |
|
||
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|
||
// | ... |
|
||
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|
||
// | AU-header(n) |
|
||
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|
||
// | pading bits |
|
||
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|
|
||
// 当 sizelength=6;indexlength=2;indexdeltalength=2 时
|
||
// 单帧封装时，rtp payload的长度 = AU-header-lengths(两个字节) + AU-header(6+2) + AU的长度
|
||
func (fe *mpesFrameExtractor) Extract(packet *Packet) (err error) {
|
||
return fe.extractFunc(packet)
|
||
}
|
||
|
||
func (fe *mpesFrameExtractor) extractFor2ByteAUHeader(packet *Packet) (err error) {
|
||
payload := packet.Payload()
|
||
|
||
// AU-headers-length 2bytes
|
||
auHeadersLength := uint16(0) | (uint16(payload[0]) << 8) | uint16(payload[1])
|
||
// AU-headers-length / 16
|
||
auHeadersCount := auHeadersLength >> 4
|
||
// AU 帧数据偏移位置
|
||
framesPayloadOffset := 2 + int(auHeadersCount)<<1
|
||
|
||
auHeaders := payload[2:framesPayloadOffset]
|
||
framesPayload := payload[framesPayloadOffset:]
|
||
frameTimeStamp := packet.Timestamp
|
||
for i := 0; i < int(auHeadersCount); i++ {
|
||
auHeader := uint16(0) | (uint16(payload[0]) << 8) | uint16(payload[1])
|
||
frameSize := auHeader >> fe.indexLength
|
||
frame := &Frame{
|
||
FrameAudio,
|
||
frameTimeStamp,
|
||
framesPayload[:frameSize],
|
||
}
|
||
if err = fe.w.Write(frame); err != nil {
|
||
return
|
||
}
|
||
|
||
// 下一帧
|
||
auHeaders = auHeaders[2:]
|
||
framesPayload = framesPayload[frameSize:]
|
||
frameTimeStamp += aac.SamplesPerFrame // 每帧采样数
|
||
}
|
||
|
||
return
|
||
}
|
||
|
||
func (fe *mpesFrameExtractor) extractFor1ByteAUHeader(packet *Packet) (err error) {
|
||
payload := packet.Payload()
|
||
|
||
// AU-headers-length 2bytes
|
||
auHeadersLength := uint16(0) | (uint16(payload[0]) << 8) | uint16(payload[1])
|
||
// AU-headers-length / 16
|
||
auHeadersCount := auHeadersLength >> 4
|
||
// AU 帧数据偏移位置
|
||
framesPayloadOffset := 2 + int(auHeadersCount)
|
||
|
||
auHeaders := payload[2:framesPayloadOffset]
|
||
framesPayload := payload[framesPayloadOffset:]
|
||
frameTimeStamp := packet.Timestamp
|
||
for i := 0; i < int(auHeadersCount); i++ {
|
||
auHeader := payload[0]
|
||
frameSize := auHeader >> fe.indexLength
|
||
frame := &Frame{
|
||
FrameAudio,
|
||
frameTimeStamp,
|
||
framesPayload[:frameSize],
|
||
}
|
||
if err = fe.w.Write(frame); err != nil {
|
||
return
|
||
}
|
||
|
||
// 下一帧
|
||
auHeaders = auHeaders[1:]
|
||
framesPayload = framesPayload[frameSize:]
|
||
frameTimeStamp += aac.SamplesPerFrame // 每帧采样数
|
||
}
|
||
|
||
return
|
||
}
|