ffmpeg系列：使用C++类封装ffmpeg，封装视频帧缩放转换rgb功能ToRGB()方法

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我是靠谱客的博主纯真皮卡丘，最近开发中收集的这篇文章主要介绍ffmpeg系列：使用C++类封装ffmpeg，封装视频帧缩放转换rgb功能ToRGB()方法，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

新增bool ToRGB(const AVFrame *yuv,char *out,int outWidth,int outHeight)方法

MyFFmpeg.h文件：

#pragma once
extern "C"{
#include <libavformat/avformat.h>
#include <libswscale/swscale.h>
}
#include <string>
#include <QMutex>
class MyFFmpeg
{
public:
	/*设置成为单件模式*/
	static MyFFmpeg *Get()
	{
		static MyFFmpeg ff;
		return &ff;
	}

	/**
	 *打开指定路径的视频文件，如果已有打开的视频文件则先关闭
	 */
	bool Open(const char *path);

	//关闭之前打开的视频文件
	void Close();

	//读取视频帧
	AVPacket Read();
	//解码功能
	AVFrame *Decode(const AVPacket *pkt);
	//缩放转换为RGB
	bool ToRGB(const AVFrame *yuv,char *out,int outWidth,int outHeight);
	/*获取相关错误信息*/
	std::string GetError();

	/*类析构函数*/
	virtual ~MyFFmpeg();

	/*视频文件总的毫秒数*/
	int totalMs = 0;
	int videoStream = 0;
protected:
	
	/*相关错误信息*/
	char errorbuf[1024];

	//应对多线程访问时的同步锁
	QMutex mutex;

	AVFormatContext *ac = NULL;
	AVFrame *yuv = NULL;
	//转换器
	SwsContext *cCtx = NULL;
	/*设置成为单件模式，所以要把构造函数设置为私有*/
	MyFFmpeg();
};

MyFFmpeg.cpp文件:

#include "MyFFmpeg.h"
#pragma comment(lib,"avformat.lib")
#pragma comment(lib,"avutil.lib")
#pragma comment(lib,"avcodec.lib")
#pragma comment(lib,"swscale.lib")
bool MyFFmpeg::Open(const char *path){
	Close();
	mutex.lock();
	int re = avformat_open_input(&ac, path, 0, 0);
	if (re != 0){//打开文件失败
		mutex.unlock();
		av_strerror(re, errorbuf, sizeof(errorbuf));
		return false;
	}
	//得到视频总时长的毫秒数
	totalMs = ((ac->duration / AV_TIME_BASE)*1000);
	for (int i = 0; i < ac->nb_streams; i++)
	{
		AVCodecContext *enc = ac->streams[i]->codec;
		
		if (enc->codec_type == AVMEDIA_TYPE_VIDEO){
			videoStream = i;
			AVCodec *codec = avcodec_find_decoder(enc->codec_id);
			if (!codec){
				mutex.unlock();
				printf("无法解码此视频文件n");
				return false;
			}
			int err = avcodec_open2(enc, codec, NULL);
			if (err != 0){
				mutex.unlock();
				char buf[1024] = { 0 };
				av_strerror(err, buf, sizeof(buf));
				printf(buf);
				return false;
			}
			printf("n");
			printf("成功打开视频编码流n");
		}
	}
	mutex.unlock();
	return true;
}
void MyFFmpeg::Close(){
	mutex.lock();
	if (ac) avformat_close_input(&ac);
	if (yuv) av_frame_free(&yuv);
	if (cCtx){
		sws_freeContext(cCtx);
		cCtx = NULL;
	}
	mutex.unlock();
}
std::string MyFFmpeg::GetError(){
	mutex.lock();
	std::string re = this->errorbuf;
	mutex.unlock();
	return re;
}

AVPacket MyFFmpeg::Read(){
	AVPacket pkt;
	memset(&pkt, 0, sizeof(AVPacket));
	mutex.lock();
	if (!ac){
		mutex.unlock();
		return pkt;
	}
	int err = av_read_frame(ac, &pkt);
	if (err != 0){//读取失败
		av_strerror(err, errorbuf, sizeof(errorbuf));
	}
	mutex.unlock();
	return pkt;
}
AVFrame * MyFFmpeg::Decode(const AVPacket *pkt){
	mutex.lock();
	if (!ac){
		mutex.unlock();
		return NULL;
	}
	if (yuv == NULL){
		yuv = av_frame_alloc();
	}
	int re = avcodec_send_packet(ac->streams[pkt->stream_index]->codec, pkt);
	if (re != 0){//失败
		mutex.unlock();
		return NULL;
	}
	re = avcodec_receive_frame(ac->streams[pkt->stream_index]->codec, yuv);
	if (re != 0){//失败
		mutex.unlock();
		return NULL;
	}
	mutex.unlock();
	return yuv;
}
bool MyFFmpeg::ToRGB(const AVFrame *yuv, char *out, int outWidth, int outHeight){
	mutex.lock();
	if (!ac){
		mutex.unlock();
		return false;
	}
	AVCodecContext *videoCtx = ac->streams[this->videoStream]->codec;
	//打开ffmpeg格式转换和缩放器
		cCtx = sws_getCachedContext(cCtx, videoCtx->width, videoCtx->height, videoCtx->pix_fmt,
			outWidth, outHeight, AV_PIX_FMT_BGRA, SWS_BICUBIC,
			NULL, NULL, NULL);
		if (!cCtx){
			mutex.unlock();
			printf("sws_getCachedContext failed!n");
			return false;
		}
		uint8_t *data[AV_NUM_DATA_POINTERS] = {0};
		data[0] = (uint8_t *)out;
		int linesize[AV_NUM_DATA_POINTERS] = { 0 };
		linesize[0] = outWidth * 4;
		int h = sws_scale(cCtx, yuv->data, yuv->linesize, 0, videoCtx->height, data, linesize);
		if (h > 0){
			printf("(%d)", h);
		}
	mutex.unlock();
	return true;
}

MyFFmpeg::MyFFmpeg()
{
	errorbuf[0] = '';
	av_register_all();
}


MyFFmpeg::~MyFFmpeg()
{
}

main.cpp调用：

#include "myplayer.h"
#include <QtWidgets/QApplication>
#include "MyFFmpeg.h"
int main(int argc, char *argv[])
{
	char path[1024] = "test.mp4";
	if (MyFFmpeg::Get()->Open(path)){
		printf("文件[%s]打开成功",path);
	}
	else
	{
		printf("n文件[%s]打开失败；错误信息：%s", path,MyFFmpeg::Get()->GetError().c_str());
		getchar();
		return -1;
	}
	char *rgb = new char[800 * 600 * 4];
	for (;;){
		AVPacket pkt = MyFFmpeg::Get()->Read();
		if (pkt.size == 0){
			break;
		}
		printf("pts = %lldn",pkt.pts);
		if (pkt.stream_index != MyFFmpeg::Get()->videoStream){
			av_packet_unref(&pkt);
			continue;
		}
		AVFrame *yuv = MyFFmpeg::Get()->Decode(&pkt);
		if (yuv){
			printf("解码成功 --- ");
			MyFFmpeg::Get()->ToRGB(yuv, rgb, 800, 600);
		}
		
		//释放空间
		av_packet_unref(&pkt);
	}
	
	QApplication a(argc, argv);
	MyPlayer w;
	w.show();
	return a.exec();
}

运行结果：