ffmpeg封装和解封装介绍-（8）解封装和封装重构

头文件：

xformat.h


#pragma once/// 封装和解封装基类#include <mutex>
struct AVFormatContext;
struct AVCodecParameters;
struct AVPacket;
struct XRational
{int num; ///< Numeratorint den; ///< Denominator
};
class XFormat
{
public:/// <summary>/// 复制参数 线程安全/// </summary>/// <param name="stream_index">对应c_->streams 下标</param>/// <param name="dst">输出参数</param>/// <returns>是否成功</returns>bool CopyPara(int stream_index, AVCodecParameters* dst);/// <summary>/// 设置上下文，并且清理上次的设置的值，如果传递NULL，相当于关闭上下文3/// 线程安全/// </summary>/// <param name="c"></param>void set_c(AVFormatContext* c);int audio_index() { return audio_index_; }int video_index() { return video_index_; }XRational video_time_base(){ return video_time_base_; }XRational audio_time_base() { return audio_time_base_; }
protected:AVFormatContext* c_ = nullptr;  //封装解封装上下文std::mutex mux_;                //c_ 资源互斥int video_index_ = 0;//video和audio在stream中索引int audio_index_ = 1;XRational video_time_base_ = {1,25};XRational audio_time_base_ = {1,9000};
};

xdemux.h

#pragma once
#include "xformat.h"
class XDemux :public XFormat
{
public:/// <summary>/// 打开解封装/// </summary>/// <param name="url">解封装地址 支持rtsp</param>/// <returns>失败返回nullptr</returns>static AVFormatContext* Open(const char* url);/// <summary>/// 读取一帧数据/// </summary>/// <param name="pkt">输出数据</param>/// <returns>是否成功</returns>bool Read(AVPacket* pkt);
};

xmux.h


#pragma once
#include "xformat.h"
//
/// 媒体封装class XMux :public XFormat
{
public://打开封装static AVFormatContext* Open(const char* url);bool WriteHead();bool Write(AVPacket* pkt);bool WriteEnd();
};

源文件：

main.cpp


#include <iostream>
#include <thread>
#include "xdemux.h"
#include "xmux.h"
using namespace std;
extern "C" { //指定函数是c语言函数，函数名不包含重载标注
//引用ffmpeg头文件
#include <libavformat/avformat.h>
}
//预处理指令导入库
#pragma comment(lib,"avformat.lib")
#pragma comment(lib,"avutil.lib")
#pragma comment(lib,"avcodec.lib")
void PrintErr(int err)
{char buf[1024] = { 0 };av_strerror(err, buf, sizeof(buf) - 1);cerr << endl;
}
#define CERR(err) if(err!=0){ PrintErr(err);getchar();return -1;}int main(int argc, char* argv[])
{//打开媒体文件const char* url = "v1080.mp4";/// 解封装//解封装输入上下文XDemux demux;auto demux_c = demux.Open(url);demux.set_c(demux_c);/// 封装//编码器上下文const char* out_url = "test_mux.mp4";XMux mux;auto mux_c = mux.Open(out_url);mux.set_c(mux_c);auto mvs = mux_c->streams[mux.video_index()]; //视频流信息auto mas = mux_c->streams[mux.audio_index()]; //视频流信息//有视频if (demux.video_index() >= 0){mvs->time_base.num = demux.video_time_base().num;mvs->time_base.den = demux.video_time_base().den;//复制视频参数demux.CopyPara(demux.video_index(), mvs->codecpar);}//有音频if (demux.audio_index() >= 0){mas->time_base.num = demux.audio_time_base().num;mas->time_base.den = demux.audio_time_base().den;//复制音频参数demux.CopyPara(demux.audio_index(), mas->codecpar);}mux.WriteHead();/// 截取10 ~ 20 秒之间的音频视频 取多不取少// 假定 9 11秒有关键帧 我们取第9秒double begin_sec = 10.0;    //截取开始时间double end_sec = 20.0;      //截取结束时间long long begin_pts = 0;long long begin_audio_pts = 0;  //音频的开始时间long long end_pts = 0;AVPacket pkt;for (;;){if (!demux.Read(&pkt)){break;}pkt.pos = -1;//写入音视频帧 会清理pktmux.Write(&pkt);}//写入结尾 包含文件偏移索引mux.WriteEnd();/*re = av_write_trailer(ec);if (re != 0)PrintErr(re);*///avformat_close_input(&ic);demux.set_c(nullptr);mux.set_c(nullptr);getchar();return 0;
}

xformat.cpp

#include "xformat.h"
#include <iostream>
#include <thread>
using namespace std;
extern "C" { //指定函数是c语言函数，函数名不包含重载标注
//引用ffmpeg头文件
#include <libavformat/avformat.h>
}
//预处理指令导入库
#pragma comment(lib,"avformat.lib")
#pragma comment(lib,"avutil.lib")
using namespace std;
void XFormat::set_c(AVFormatContext* c)
{unique_lock<mutex> lock(mux_);if (c_) //清理原值{if (c_->oformat) //输出上下文{if (c_->pb)avio_closep(&c_->pb);avformat_free_context(c_);}else if (c_->iformat)  //输入上下文{avformat_close_input(&c_);}else{avformat_free_context(c_);}}c_ = c;if (!c_)return;//用于区分是否有音频或者视频流audio_index_ = -1;video_index_ = -1;//区分音视频stream 索引for (int i = 0; i < c->nb_streams; i++){//音频if (c->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_AUDIO){audio_index_ = i;audio_time_base_.den = c->streams[i]->time_base.den;audio_time_base_.num = c->streams[i]->time_base.num;}else if (c->streams[i]->codecpar->codec_type == AVMEDIA_TYPE_VIDEO){video_index_ = i;video_time_base_.den = c->streams[i]->time_base.den;video_time_base_.num = c->streams[i]->time_base.num;}}
}/// <summary>
/// 复制参数 线程安全
/// </summary>
/// <param name="stream_index">对应c_->streams 下标</param>
/// <param name="dst">输出参数</param>
/// <returns>是否成功</returns>
bool XFormat::CopyPara(int stream_index, AVCodecParameters* dst)
{unique_lock<mutex> lock(mux_);if (!c_){return false;}if (stream_index<0 || stream_index>c_->nb_streams)return false;auto re = avcodec_parameters_copy(dst, c_->streams[stream_index]->codecpar);if (re < 0){return false;}return true;
}

xdemux.cpp

#include "xdemux.h"
#include <iostream>
#include <thread>
using namespace std;
extern "C" { //指定函数是c语言函数，函数名不包含重载标注
//引用ffmpeg头文件
#include <libavformat/avformat.h>
}
static void PrintErr(int err)
{char buf[1024] = { 0 };av_strerror(err, buf, sizeof(buf) - 1);cerr << buf << endl;
}
#define BERR(err) if(err!= 0){PrintErr(err);return 0;}
AVFormatContext* XDemux::Open(const char* url)
{AVFormatContext* c = nullptr;//打开封装上下文auto re = avformat_open_input(&c, url, nullptr, nullptr);BERR(re);//获取媒体信息re = avformat_find_stream_info(c, nullptr);BERR(re);//打印输入封装信息av_dump_format(c, 0, url, 0);return c;
}bool XDemux::Read(AVPacket* pkt)
{unique_lock<mutex> lock(mux_);if (!c_)return false;auto re = av_read_frame(c_, pkt);BERR(re);return true;
}

xmux.cpp


#include "xmux.h"#include <iostream>
#include <thread>
using namespace std;
extern "C" { //指定函数是c语言函数，函数名不包含重载标注
//引用ffmpeg头文件
#include <libavformat/avformat.h>
}
static void PrintErr(int err)
{char buf[1024] = { 0 };av_strerror(err, buf, sizeof(buf) - 1);cerr << buf << endl;
}
#define BERR(err) if(err!= 0){PrintErr(err);return 0;}//打开封装
AVFormatContext* XMux::Open(const char* url)
{AVFormatContext* c = nullptr;//创建上下文auto re = avformat_alloc_output_context2(&c, NULL, NULL, url);BERR(re);//添加视频音频流auto vs = avformat_new_stream(c, NULL);   //视频流vs->codecpar->codec_type = AVMEDIA_TYPE_VIDEO;auto as = avformat_new_stream(c, NULL);   //音频流as->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;//打开IOre = avio_open(&c->pb, url, AVIO_FLAG_WRITE);BERR(re);return c;
}
bool XMux::Write(AVPacket* pkt)
{unique_lock<mutex> lock(mux_);if (!c_)return false;//写入一帧数据，内部缓冲排序dts，通过pkt=null 可以写入缓冲auto re = av_interleaved_write_frame(c_,pkt);BERR(re);return true;
}bool XMux::WriteEnd()
{unique_lock<mutex> lock(mux_);if (!c_)return false;av_interleaved_write_frame(c_, nullptr);//写入排序缓冲auto re = av_write_trailer(c_);BERR(re);return true;
}
bool XMux::WriteHead()
{unique_lock<mutex> lock(mux_);if (!c_)return false;auto re = avformat_write_header(c_, nullptr);BERR(re);//打印输出上下文av_dump_format(c_, 0, c_->url, 1);return true;
}