使用ffmpeg实现解码并保存为yuv文件

通过ffmpeg实现解码并保存为yuv文件

/**
* 抽取ffmpeg中的函数接口实现视频解码并保存
*/


#define __STDC_CONSTANT_MACROS
#include 

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"
};


char* filename = "720p.m2v";

int main()
{
	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();
	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



	AVFrame* pFrameYUV;
	int sizeYUV = avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
	pFrameYUV = avcodec_alloc_frame();

	printf(" sizeYUV: %d\n", sizeYUV);

	uint8_t *out_yuv_buffer = (uint8_t *)av_malloc(sizeYUV);
	avpicture_fill((AVPicture *)pFrameYUV, out_yuv_buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
	FILE* fpYUV = fopen("demo.yuv", "wb+");
	if (!fpYUV)
	{
		printf("文件打开失败！\n");
		return -1;
	}


	AVPacket* packet = (AVPacket*)malloc(sizeof(AVPacket));
	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, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL); 


	int ret;
	int got_picture;

	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)
				{
					printf(" %d ", got_picture);
					sws_scale(img_convert_ctx, (const uint8_t* const*)pAvFrame->data, pAvFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);
					int size_temp;
					size_temp = pCodecCtx->height * pCodecCtx->width;
					fwrite(pFrameYUV->data[0], 1,size_temp, fpYUV);
					fwrite(pFrameYUV->data[1], 1,size_temp/4, fpYUV);
					fwrite(pFrameYUV->data[2], 1,size_temp/4, fpYUV);
				}
			}
			av_free_packet(packet);
		}
		else 
		{
			break;
		}
	}
	//FIX: Flush Frames remained in Codec
	while (1) 
	{
		ret = avcodec_decode_video2(pCodecCtx, pAvFrame, &got_picture, packet);
		if (ret < 0)
			break;
		if (!got_picture)
			break;
		sws_scale(img_convert_ctx, (const uint8_t* const*)pAvFrame->data, pAvFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);

		int y_size=pCodecCtx->width*pCodecCtx->height;  
		fwrite(pFrameYUV->data[0],1,y_size,fpYUV);    //Y 
		fwrite(pFrameYUV->data[1],1,y_size/4,fpYUV);  //U
		fwrite(pFrameYUV->data[2],1,y_size/4,fpYUV);  //V

	}

	av_free(pFrameYUV);
	av_free(pAvFrame);
	av_free(out_yuv_buffer);
	avcodec_close(pCodecCtx);
	avformat_close_input(&pFormatCtx);
	sws_freeContext(img_convert_ctx);

	fclose(fpYUV);
	return 0;
}