音视频面经_音视频知识解析：第五章 整合实现视频播放器

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专栏地址：音视频面经_音视频知识解析

------------下面正文开始------------

1 整合方式

• FFmpeg解码器实现了：视频文件->YUV

• SDL视频显示实现了：YUV->屏幕

• FFmpeg+SDL整合之后实现了：视频文件->YUV->屏幕

2 进阶：脱离开发环境的独立播放器

因为VS会生成可执行文件（在Debug文件夹中），利用argv参数进行视频文件的选择播放

main()函数的参数

• argc argv：全称为ARGument Counter 和 ARGument Vector。其中argv存储了来自于命令行的参数；而argc存储了参数的个数。

• 例如在命令行中输入“ffmpeg -i test.mkv test.ts ”，则argc取值为4， 而argv[]数组取值如下：

argv[0]=“ffmpeg”

argv[1]=“-i”

argv[2]=“test.mkv”

argv[3]=“test.ts”

• 动态链接库（*.dll）

动态链接库不能被编译进应用程序。因而使用应用程序的时候必须在相同目录下保存用到的动态链接库文件。

3 练习

• 修改源代码。整合《Ffmpeg视频解码器》和《SDL视频显示器》形成视频播放器，要求

▫ 可以提取并打印视频文进相关的信息

▫ 可以脱离开发环境，在命令行下播放任意一个视频文件

▫ 可以暂停/继续播放

// ffmpegSdlPlayer.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.h"

#include <stdio.h>

#define __STDC_CONSTANT_MACROS

extern "C"
{
#include "libavcodec/avcodec.h"
#include "libavformat/avformat.h"
#include "libswscale/swscale.h"
#include "SDL2/SDL.h"
};


//Refresh Event
#define SFM_REFRESH_EVENT  (SDL_USEREVENT + 1)

#define SFM_BREAK_EVENT  (SDL_USEREVENT + 2)

int thread_exit=0;

int sfp_refresh_thread(void *opaque){
	thread_exit=0;
	while (!thread_exit) {
		SDL_Event event;
		event.type = SFM_REFRESH_EVENT;
		SDL_PushEvent(&event);
		SDL_Delay(40);
	}
	thread_exit=0;
	//Break
	SDL_Event event;
	event.type = SFM_BREAK_EVENT;
	SDL_PushEvent(&event);

	return 0;
}


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

	AVFormatContext	*pFormatCtx;
	int				i, videoindex;
	AVCodecContext	*pCodecCtx;
	AVCodec			*pCodec;
	AVFrame	*pFrame,*pFrameYUV;
	uint8_t *out_buffer;
	AVPacket *packet;
	int ret, got_picture;

	//------------SDL----------------
	int screen_w,screen_h;
	SDL_Window *screen; 
	SDL_Renderer* sdlRenderer;
	SDL_Texture* sdlTexture;
	SDL_Rect sdlRect;
	SDL_Thread *video_tid;
	SDL_Event event;

	struct SwsContext *img_convert_ctx;

	char filepath[]="屌丝男士.mov";

	av_register_all();
	avformat_network_init();
	pFormatCtx = avformat_alloc_context();

	if(avformat_open_input(&pFormatCtx,filepath,NULL,NULL)!=0){
		printf("Couldn't open input stream.\n");
		return -1;
	}
	if(avformat_find_stream_info(pFormatCtx,NULL)<0){
		printf("Couldn't find stream information.\n");
		return -1;
	}
	videoindex=-1;
	for(i=0; i<pFormatCtx->nb_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.\n");
		return -1;
	}
	pCodecCtx=pFormatCtx->streams[videoindex]->codec;
	pCodec=avcodec_find_decoder(pCodecCtx->codec_id);
	if(pCodec==NULL){
		printf("Codec not found.\n");
		return -1;
	}
	if(avcodec_open2(pCodecCtx, pCodec,NULL)<0){
		printf("Could not open codec.\n");
		return -1;
	}
	pFrame=av_frame_alloc();
	pFrameYUV=av_frame_alloc();
	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);
	
	img_convert_ctx = sws_getContext(pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt, 
		pCodecCtx->width, pCodecCtx->height, PIX_FMT_YUV420P, SWS_BICUBIC, NULL, NULL, NULL); 
	

	if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_TIMER)) {  
		printf( "Could not initialize SDL - %s\n", SDL_GetError()); 
		return -1;
	} 
	//SDL 2.0 Support for multiple windows
	screen_w = pCodecCtx->width;
	screen_h = pCodecCtx->height;
	screen = SDL_CreateWindow("Simplest ffmpeg player's Window", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
		screen_w, screen_h,SDL_WINDOW_OPENGL);

	if(!screen) {  
		printf("SDL: could not create window - exiting:%s\n",SDL_GetError());  
		return -1;
	}
	sdlRenderer = SDL_CreateRenderer(screen, -1, 0);  
	//IYUV: Y + U + V  (3 planes)
	//YV12: Y + V + U  (3 planes)
	sdlTexture = SDL_CreateTexture(sdlRenderer, SDL_PIXELFORMAT_IYUV, SDL_TEXTUREACCESS_STREAMING,pCodecCtx->width,pCodecCtx->height);  

	sdlRect.x=0;
	sdlRect.y=0;
	sdlRect.w=screen_w;
	sdlRect.h=screen_h;

	packet=(AVPacket *)av_malloc(sizeof(AVPacket));

	video_tid = SDL_CreateThread(sfp_refresh_thread,NULL,NULL);
	//------------SDL End------------
	//Event Loop
	
	for (;;) {
		//Wait
		SDL_WaitEvent(&event);
		if(event.type==SFM_REFRESH_EVENT){
			//------------------------------
			if(av_read_frame(pFormatCtx, packet)>=0){
				if(packet->stream_index==videoindex){
					ret = avcodec_decode_video2(pCodecCtx, pFrame, &got_picture, packet);
					if(ret < 0){
						printf("Decode Error.\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);
						//SDL---------------------------
						SDL_UpdateTexture( sdlTexture, NULL, pFrameYUV->data[0], pFrameYUV->linesize[0] );  
						SDL_RenderClear( sdlRenderer );  
						//SDL_RenderCopy( sdlRenderer, sdlTexture, &sdlRect, &sdlRect );  
						SDL_RenderCopy( sdlRenderer, sdlTexture, NULL, NULL);  
						SDL_RenderPresent( sdlRenderer );  
						//SDL End-----------------------
					}
				}
				av_free_packet(packet);
			}else{
				//Exit Thread
				thread_exit=1;
			}
		}else if(event.type==SDL_QUIT){
			thread_exit=1;
		}else if(event.type==SFM_BREAK_EVENT){
			break;
		}

	}

	sws_freeContext(img_convert_ctx);

	SDL_Quit();
	//--------------
	av_frame_free(&pFrameYUV);
	av_frame_free(&pFrame);
	avcodec_close(pCodecCtx);
	avformat_close_input(&pFormatCtx);

	return 0;
}

本专栏会持续更新优质内容，敬请订阅，关注更新。

专栏地址：音视频面经_音视频知识解析

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