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aac 和 h264 封装为视频流，封装为c++的Muxter类

流程

• 分配视频文件上下文
  int Init(const char *url);

• 创建流，赋值给视频的音频流和视频流
  int AddStream(AVCodecContext *codec_ctx);

• 写视频流的head
  int SendHeader();

• 写视频流的packet，需要转换packet的pts和dts , 值为 原有pts * 编码时间基/ 视频流的时间基
  int SendPacket(AVPacket *packet)

• 写视频流的trail
  int SendTrailer();

• 释放资源
  void DeInit();

api

int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const
// 时间基转换函数 , 计算结果为 a * bq / cq

核心代码

muxer.h

#ifndef MUXER_H
#define MUXER_H
#include <iostream>
extern "C"
{
#include "libavformat/avformat.h"
#include "libavcodec/avcodec.h"
}class Muxer
{
public:Muxer();~Muxer();// 输出文件 返回<0值异常// 初始化int Init(const char *url);// 资源释放void DeInit();// 创建流int AddStream(AVCodecContext *codec_ctx);// 写流int SendHeader();int SendPacket(AVPacket *packet);int SendTrailer();int Open(); // avio open
private:AVFormatContext *fmt_ctx_ = NULL;std::string url_ = "";// 编码器上下文AVCodecContext *aud_codec_ctx_= NULL;AVStream *aud_stream_ = NULL;AVCodecContext *vid_codec_ctx_= NULL;AVStream *vid_stream_ = NULL;int audio_index_ = -1;int video_index_ = -1;
};#endif // MUXER_H

muxer.cpp

 #include "muxer.h"Muxer::Muxer()
{}Muxer::~Muxer()
{}int Muxer::Init(const char *url)
{int ret = avformat_alloc_output_context2(&fmt_ctx_, NULL, NULL,url);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avformat_alloc_output_context2 failed:%s\n", ret);return -1;}url_ = url;return 0;
}void Muxer::DeInit()
{if(fmt_ctx_) {avformat_close_input(&fmt_ctx_);}url_ = "";aud_codec_ctx_ = NULL;aud_stream_ = NULL;audio_index_ = -1;vid_codec_ctx_ = NULL;vid_stream_ = NULL;video_index_ = -1;
}int Muxer::AddStream(AVCodecContext *codec_ctx)
{if(!fmt_ctx_) {printf("fmt ctx is NULL\n");return -1;}if(!codec_ctx) {printf("codec ctx is NULL\n");return -1;}AVStream *st = avformat_new_stream(fmt_ctx_, NULL);if(!st) {printf("avformat_new_stream failed\n");return -1;}//    st->codecpar->codec_tag = 0;// 从编码器上下文复制, 根据提供的编解码器的值填充参数结构avcodec_parameters_from_context(st->codecpar, codec_ctx);av_dump_format(fmt_ctx_, 0, url_.c_str(), 1);// 判断当前的是视频流还是音频流if(codec_ctx->codec_type == AVMEDIA_TYPE_AUDIO) {aud_codec_ctx_ = codec_ctx;aud_stream_ = st;audio_index_ = st->index;}  else if(codec_ctx->codec_type == AVMEDIA_TYPE_VIDEO) {vid_codec_ctx_ = codec_ctx;vid_stream_ = st;video_index_ = st->index;}return 0;
}int Muxer::SendHeader()
{if(!fmt_ctx_) {printf("fmt ctx is NULL\n");return -1;}int ret = avformat_write_header(fmt_ctx_, NULL);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avformat_write_header failed:%s\n", ret);return -1;}return 0;
}int Muxer::SendPacket(AVPacket *packet)
{int stream_index = packet->stream_index;if(!packet || packet->size <= 0 || !packet->data) {printf("packet is null\n");if(packet)av_packet_free(&packet);return -1;}AVRational src_time_base;   // 编码后的包AVRational dst_time_base;   // mp4输出文件对应流的time_baseif(vid_stream_ && vid_codec_ctx_ && stream_index == video_index_) {src_time_base = vid_codec_ctx_->time_base;dst_time_base = vid_stream_->time_base;} else if(aud_stream_ && aud_codec_ctx_ && stream_index == audio_index_) {src_time_base = aud_codec_ctx_->time_base;dst_time_base = aud_stream_->time_base;}// 时间基转换// int64_t av_rescale_q(int64_t a, AVRational bq, AVRational cq) av_const;// 时间基转换函数  a * bq / cqpacket->pts = av_rescale_q(packet->pts, src_time_base, dst_time_base);packet->dts = av_rescale_q(packet->dts, src_time_base, dst_time_base);packet->duration = av_rescale_q(packet->duration, src_time_base, dst_time_base);int ret = 0;//写packetret = av_interleaved_write_frame(fmt_ctx_, packet); // 不是立即写入文件，内部缓存，主要是对pts进行排序//    ret = av_write_frame(fmt_ctx_, packet);av_packet_free(&packet);if(ret == 0) {return 0;}else {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("avformat_write_header failed:%s\n", ret);return -1;}
}int Muxer::SendTrailer()
{if(!fmt_ctx_) {printf("fmt ctx is NULL\n");return -1;}int ret = av_write_trailer(fmt_ctx_);if(ret != 0) {char errbuf[1024] = {0};av_strerror(ret, errbuf, sizeof(errbuf) - 1);printf("av_write_trailer failed:%s\n", ret);return -1;}return 0;
}