基于FFmpeg的内存播放器源码解析

FFmpeg不仅仅是对文件进行“读，写”操作，而是要对内存进行“读，写”操作。因此打算记录的就是使用FFmpeg对内存进行读写的例子。在内存中读出相应的视频帧信息，通过解码相应的内存视频帧信息，通过sdl库播放出来。

程序源代码如下：

/**
 * 最简单的基于FFmpeg的内存读写例子（内存播放器）
 * Simplest FFmpeg mem Player
 *

 *
 * 本程序实现了对内存中的视频数据的播放。
 * 是最简单的使用FFmpeg读内存的例子。
 *
 * This software play video data in memory (not a file).
 * It's the simplest example to use FFmpeg to read from memory.
 *
 */


#include 

extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
	//SDL
#include "sdl/SDL.h"
#include "sdl/SDL_thread.h"
};

//Output YUV420P 
#define OUTPUT_YUV420P 0
FILE *fp_open=NULL;

//Callback
int read_buffer(void *opaque, uint8_t *buf, int buf_size){
	if(!feof(fp_open)){
		int true_size=fread(buf,1,buf_size,fp_open);
		return true_size;
	}else{
		return -1;
	}

}


int main(int argc, char* argv[])
{

	AVFormatContext	*pFormatCtx;
	int				i, videoindex;
	AVCodecContext	*pCodecCtx;
	AVCodec			*pCodec;
	char filepath[]="ccd_receive1.ts";
	
	av_register_all();
	avformat_network_init();
	pFormatCtx = avformat_alloc_context();
	
	fp_open=fopen(filepath,"rb+");
	//AVIOContext中的缓存
	unsigned char *aviobuffer=(unsigned char *)av_malloc(32768);
	AVIOContext *avio =avio_alloc_context(aviobuffer, 32768,0,NULL,read_buffer,NULL,NULL);
	//设置相应的视频文件为内存文件
	pFormatCtx->pb=avio;
	// 打开相应的内存视频流
	if(avformat_open_input(&pFormatCtx,NULL,NULL,NULL)!=0){
		printf("Couldn't open input stream.（无法打开输入流）\n");
		return -1;
	}
	if(av_find_stream_info(pFormatCtx)<0){
		printf("Couldn't find stream information.（无法获取流信息）\n");
		return -1;
	}
	videoindex=-1;
	//查看其中是否有相应的视频文件
	for(i=0; inb_streams; i++) 
		if(pFormatCtx->streams[i]->codec->codec_type==AVMEDIA_TYPE_VIDEO){
			videoindex=i;
			break;
		}
	if(videoindex==-1){
		printf("Didn't find a video stream.（没有找到视频流）\n");
		return -1;
	}
	pCodecCtx=pFormatCtx->streams[videoindex]->codec;
	pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
	if(pCodec==NULL){
		printf("Codec not found.（没有找到解码器）\n");
		return -1;
	}
	if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){
		printf("Could not open codec.（无法打开解码器）\n");
		return -1;
	}
	AVFrame	*pFrame,*pFrameYUV;
	pFrame=avcodec_alloc_frame();
	pFrameYUV=avcodec_alloc_frame();
	uint8_t *out_buffer=(uint8_t *)av_malloc(avpicture_get_size(PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height));
	avpicture_fill((AVPicture *)pFrameYUV, out_buffer, PIX_FMT_YUV420P, pCodecCtx->width, pCodecCtx->height);
	//SDL----------------------------
	if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)) {  
		printf( "Could not initialize SDL - %s\n", SDL_GetError()); 
		return -1;
	} 

	int screen_w=0,screen_h=0;
	SDL_Surface *screen; 
	screen_w = pCodecCtx->width;
	screen_h = pCodecCtx->height;
	screen = SDL_SetVideoMode(screen_w, screen_h, 0,0);

	if(!screen) {  
		printf("SDL: could not set video mode - exiting:%s\n",SDL_GetError());  
		return -1;
	}
	SDL_Overlay *bmp; 
	//设置sdl播放器
	bmp = SDL_CreateYUVOverlay(pCodecCtx->width, pCodecCtx->height,SDL_YV12_OVERLAY, screen); 
	SDL_Rect rect;
	//SDL End------------------------
	int ret, got_picture;

	AVPacket *packet=(AVPacket *)av_malloc(sizeof(AVPacket));
	//Output Information-----------------------------
	printf("File Information---------------------------------\n");
	av_dump_format(pFormatCtx,0,filepath,0);
	printf("-------------------------------------------------\n");

#if OUTPUT_YUV420P 
    FILE *fp_yuv=fopen("output.yuv","wb+");  
#endif  

	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); 
	//------------------------------
	//获取相应的内存中的某一视频帧
	while(av_read_frame(pFormatCtx, packet)>=0){
		if(packet->stream_index==videoindex){
			//解码相应的视频帧信息到got_picture数据结构中
			ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
			if(ret < 0){
				printf("Decode Error.（解码错误）\n");
				return -1;
			}
			if(got_picture){
				sws_scale(img_convert_ctx, (const uint8_t* const*)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameYUV->data, pFrameYUV->linesize);
#if OUTPUT_YUV420P
				int y_size=pCodecCtx->width*pCodecCtx->height;  
				fwrite(pFrameYUV->data[0],1,y_size,fp_yuv);    //Y 
				fwrite(pFrameYUV->data[1],1,y_size/4,fp_yuv);  //U
				fwrite(pFrameYUV->data[2],1,y_size/4,fp_yuv);  //V
#endif
				SDL_LockYUVOverlay(bmp);
				bmp->pixels[0]=pFrameYUV->data[0];
				bmp->pixels[2]=pFrameYUV->data[1];
				bmp->pixels[1]=pFrameYUV->data[2];     
				bmp->pitches[0]=pFrameYUV->linesize[0];
				bmp->pitches[2]=pFrameYUV->linesize[1];   
				bmp->pitches[1]=pFrameYUV->linesize[2];
				SDL_UnlockYUVOverlay(bmp); 
				rect.x = 0;    
				rect.y = 0;    
				rect.w = screen_w;    
				rect.h = screen_h;  
				//显示内存中解码的相应的视频帧信息
				SDL_DisplayYUVOverlay(bmp, &rect); 
				//Delay 40ms
				SDL_Delay(40);
			}
		}
		av_free_packet(packet);
	}
	sws_freeContext(img_convert_ctx);

#if OUTPUT_YUV420P 
    fclose(fp_yuv);
#endif 

	fclose(fp_open);

	SDL_Quit();

	av_free(out_buffer);
	av_free(pFrameYUV);
	avcodec_close(pCodecCtx);
	avformat_close_input(&pFormatCtx);

	return 0;
}

可以通过代码定义的宏来确定是否将解码后的YUV420P数据输出成文件：

#define OUTPUT_YUV420P 0

结果

程序的运行结果如下。可以解码播放测试视频。

相应的代码下载地址

https://download.csdn.net/download/tigerxuchuanli/10358868