FFmpeg + Opencv 解码和显示

利用FFmpeg开源编解码库实现解码，转换为Mat格式后，使用Opencv显示

/**
* 抽取ffmpeg中的函数接口实现视频解码
* 再通过Opencv中的函数接口播放,同时开启两个视频进行操作
*/


#define __STDC_CONSTANT_MACROS
#include <stdio.h>
#include <Windows.h>
#include <process.h>

// Opencv
#include <opencv/cv.h>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>


extern "C"
{
#include "libavutil/avutil.h"
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
	//新版里的图像转换结构需要引入的头文件
#include "libswscale/swscale.h"
};


using namespace cv;

//char* filename = "cuc_ieschool.flv";
char* filename = "video0.avi";

DWORD WINAPI ffmpeg_decoder(LPVOID pM);


HANDLE g_semphore = {NULL};

cv::Mat pCvMat;
bool g_cvShow = true; //是否显示视频

int main()
{

	g_semphore = CreateSemaphore(NULL, 0, 1, NULL);
	HANDLE handle_video = CreateThread(NULL, 0, ffmpeg_decoder, (LPVOID)filename, 0, NULL);

	//////////////////////////////////////////////////////////////////////////
#if 1
	cv::Mat pCvMatCopy = pCvMat;
	namedWindow("cvRGB", 1);
	int i = 0;
	while (g_cvShow)
	{
		cv::imshow("cvRGB", pCvMatCopy);
		printf("%d",i);
		++i;
	}
	cvDestroyWindow("cvRGB");
#endif
	/////////////////////////////////////////////////////////////////////////

	WaitForSingleObject(g_semphore, INFINITE);

	CloseHandle(g_semphore);
	CloseHandle(handle_video);

	getchar();
	return 0;
}

//ffmpeg解码
DWORD WINAPI ffmpeg_decoder(LPVOID pM)
{
	AVCodec *pCodec; //解码器指针
	AVCodecContext* pCodecCtx; //ffmpeg解码类的类成员
	AVFrame* pAvFrame; //多媒体帧，保存解码后的数据帧
	AVFormatContext* pFormatCtx; //保存视频流的信息

	av_register_all(); //注册库中所有可用的文件格式和编码器

	pFormatCtx = avformat_alloc_context();

	char *filename = (char *)pM;//convert value type
	if (avformat_open_input(&pFormatCtx, filename, NULL, NULL) != 0) { //检查文件头部
		printf("Can't find the stream!\n");
	}
	if (av_find_stream_info(pFormatCtx) < 0) { //查找流信息
		printf("Can't find the stream information !\n");
	}

	int videoindex = -1;
	for (int i=0; i < pFormatCtx->nb_streams; ++i) //遍历各个流，找到第一个视频流,并记录该流的编码信息
	{
		if (pFormatCtx->streams[i]->codec->codec_type == AVMEDIA_TYPE_VIDEO) {
			videoindex = i;
			break;
		}
	}
	if (videoindex == -1) {
		printf("Don't find a video stream !\n");
		return -1;
	}
	pCodecCtx = pFormatCtx->streams[videoindex]->codec; //得到一个指向视频流的上下文指针
	pCodec = avcodec_find_decoder(pCodecCtx->codec_id); //到该格式的解码器
	if (pCodec == NULL) {
		printf("Cant't find the decoder !\n"); //寻找解码器
		return -1;
	}
	if (avcodec_open2(pCodecCtx,pCodec,NULL) < 0) { //打开解码器
		printf("Can't open the decoder !\n");
		return -1;
	}

	pAvFrame = avcodec_alloc_frame(); //分配帧存储空间
	AVFrame* pFrameBGR = avcodec_alloc_frame(); //存储解码后转换的RGB数据


	// 保存BGR，opencv中是按BGR来保存的
	int size = avpicture_get_size(AV_PIX_FMT_BGR24, pCodecCtx->width, pCodecCtx->height);
	uint8_t *out_buffer = (uint8_t *)av_malloc(size);
	avpicture_fill((AVPicture *)pFrameBGR, out_buffer, AV_PIX_FMT_BGR24, pCodecCtx->width, pCodecCtx->height); // allocator memory for BGR buffer


	AVPacket* packet = (AVPacket*)malloc(sizeof(AVPacket)); //output the video info
	printf("-----------输出文件信息---------\n");
	av_dump_format(pFormatCtx, 0, filename, 0);
	printf("------------------------------");

	struct SwsContext *img_convert_ctx;
	img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, pCodecCtx->width, pCodecCtx->height, AV_PIX_FMT_BGR24, SWS_BICUBIC, NULL, NULL, NULL); 

	//opencv,声明Mat对象，作为局部变量
	//cv::Mat pCvMat;
	pCvMat.create(cv::Size(pCodecCtx->width, pCodecCtx->height), CV_8UC3);

	int ret;
	int got_picture;

//	cvNamedWindow("RGB", 1);
	for (;;)
	{
		if(av_read_frame(pFormatCtx, packet)>=0)
		{
			if(packet->stream_index==videoindex)
			{
				ret = avcodec_decode_video2(pCodecCtx, pAvFrame, &got_picture, packet);
				if(ret < 0)
				{
					printf("Decode Error.（解码错误）\n");
					return -1;
				}
				if (got_picture)
				{
					//YUV to RGB
					sws_scale(img_convert_ctx, (const uint8_t* const*)pAvFrame->data, pAvFrame->linesize, 0, pCodecCtx->height, pFrameBGR->data, pFrameBGR->linesize);//convert yuv to BGR24

					memcpy(pCvMat.data, out_buffer, size);
//					imshow("RGB", pCvMat);
//					waitKey(1);
				}
			}
			av_free_packet(packet);
		}
		else 
		{
			break;
		}
	}
	g_cvShow = false;
	av_free(out_buffer);
	av_free(pFrameBGR);
	av_free(pAvFrame);
	avcodec_close(pCodecCtx);
	avformat_close_input(&pFormatCtx);

	sws_freeContext(img_convert_ctx);
//	cvDestroyWindow("RGB");

	ReleaseSemaphore(g_semphore, 1, NULL);
}