ffmpeg实战教程（二）用SDL播放YUV，并结合ffmpeg实现简易播放器

小鱼儿 2022-05-14 09:11 241阅读 0赞

# ffmpeg实战教程（二）用SDL播放YUV，并结合ffmpeg实现简易播放器 #

https://blog.csdn.net/King1425/article/details/71171142

## **我们先实现用SDL播放YUV数据** ##

先来了解一下基本概念

SDL基本函数：  
**\[初始化\]**  
\* SDL\_Init(): 初始化SDL。  
\* SDL\_CreateWindow(): 创建窗口（Window）。  
\* SDL\_CreateRenderer(): 基于窗口创建渲染器（Render）。  
\* SDL\_CreateTexture(): 创建纹理（Texture）。

**\[循环渲染数据\]**  
\* SDL\_UpdateTexture(): 设置纹理的数据。  
\* SDL\_RenderCopy(): 纹理复制给渲染器。  
\* SDL\_RenderPresent(): 显示。

**C中的fseek函数**  
**int fseek( FILE \*stream, long offset, int origin );**  
第一个参数stream为文件指针  
第二个参数offset为偏移量，整数表示正向偏移，负数表示负向偏移  
第三个参数origin设定从文件的哪里开始偏移,可能取值为：SEEK\_CUR、 SEEK\_END 或 SEEK\_SET  
SEEK\_SET： 文件开头  
SEEK\_CUR： 当前位置  
SEEK\_END： 文件结尾  
其中SEEK\_SET,SEEK\_CUR和SEEK\_END和依次为0，1和2.  
简言之：  
fseek(fp,100L,0);把fp指针移动到离文件开头100字节处；  
fseek(fp,100L,1);把fp指针移动到离文件当前位置100字节处；  
fseek(fp,100L,2);把fp指针退回到离文件结尾100字节处。

**下面看一下运行效果：**  
![这里写图片描述][SouthEast]

**下面看源代码 注释很详细**

#include <stdio.h>
    
    extern "C"
    {
    #include "sdl/SDL.h"
    };
    
    const int bpp=12;
    
    int screen_w=500,screen_h=500;
    const int pixel_w=1920,pixel_h=1080;
    
    unsigned char buffer[pixel_w*pixel_h*bpp/8];
    
    
    //Refresh Event
    #define REFRESH_EVENT  (SDL_USEREVENT + 1)
    
    #define BREAK_EVENT  (SDL_USEREVENT + 2)
    
    int thread_exit=0;
    
    int refresh_video(void *opaque){
        thread_exit=0;
        while (!thread_exit) {
            SDL_Event event;
            event.type = REFRESH_EVENT;
            SDL_PushEvent(&event); //发送事件 即handler
            SDL_Delay(40);
        }
        thread_exit=0;
        //Break
        SDL_Event event;//代表一个事件 声明
        event.type = BREAK_EVENT;
        SDL_PushEvent(&event);
    
        return 0;
    }
    
    int main(int argc, char* argv[])
    {
        if(SDL_Init(SDL_INIT_VIDEO)) {  //初始化SDL系统
            printf( "Could not initialize SDL - %s\n", SDL_GetError()); 
            return -1;
        } 
    
        SDL_Window *screen; 
        //SDL 2.0  创建窗口（Window）。
        screen = SDL_CreateWindow("WS Video Play SDL2", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
            screen_w, screen_h,SDL_WINDOW_OPENGL|SDL_WINDOW_RESIZABLE);
        if(!screen) {  
            printf("SDL: could not create window - exiting:%s\n",SDL_GetError());  
            return -1;
        }
        //创建基于窗口创建渲染器（Render）
        SDL_Renderer* sdlRenderer = SDL_CreateRenderer(screen, -1, 0);  
    
        Uint32 pixformat=0;
    
        //IYUV: Y + U + V  (3 planes)
        //YV12: Y + V + U  (3 planes)
        pixformat= SDL_PIXELFORMAT_IYUV;  
        //创建纹理（Texture）
        SDL_Texture* sdlTexture = SDL_CreateTexture(sdlRenderer,pixformat, SDL_TEXTUREACCESS_STREAMING,pixel_w,pixel_h);
    
        FILE *fp=NULL;
        //用我们上篇博客解码出来的yuv文件
        fp=fopen("output.yuv","rb+");
    
        if(fp==NULL){
            printf("cannot open this file\n");
            return -1;
        }
        //window 视频显示框
        SDL_Rect sdlRect;  
    
        SDL_Thread *refresh_thread = SDL_CreateThread(refresh_video,NULL,NULL);//创建线程
        SDL_Event event;
        while(1){
            //Wait等待事件 即监听
            SDL_WaitEvent(&event);
            if(event.type==REFRESH_EVENT){
                if (fread(buffer, 1, pixel_w*pixel_h*bpp/8, fp) != pixel_w*pixel_h*bpp/8){
                    // Loop
                    fseek(fp, 0, SEEK_SET);
                    fread(buffer, 1, pixel_w*pixel_h*bpp/8, fp);
                }
                //设置纹理的数据
                SDL_UpdateTexture( sdlTexture, NULL, buffer, pixel_w);  
    
                //FIX: If window is resize
                sdlRect.x = 0;  
                sdlRect.y = 0;  
                sdlRect.w = screen_w;  
                sdlRect.h = screen_h;  
    
                SDL_RenderClear( sdlRenderer ); 
                //将纹理的数据拷贝给渲染器
                SDL_RenderCopy( sdlRenderer, sdlTexture, NULL, &sdlRect);  
                //显示
                SDL_RenderPresent( sdlRenderer );  
    
            }else if(event.type==SDL_WINDOWEVENT){
                //If Resize SDL_WINDOWEVENT事件 可以拉伸播放器界面
                SDL_GetWindowSize(screen,&screen_w,&screen_h);
            }else if(event.type==SDL_QUIT){
                thread_exit=1;
            }else if(event.type==BREAK_EVENT){
                break;
            }
        }
        SDL_Quit();//退出系统
        return 0;
    }

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我们把上篇博客解码出来的YUV数据拷贝到项目跟目录，然后编译运行即可  
**配置环境以及编译运行部分看 此系列的实战（一）**  
[http://blog.csdn.net/king1425/article/details/71160339][http_blog.csdn.net_king1425_article_details_71160339]

## **下面我们结合上篇博客 把MP4解码为YUV，然后在SDL上播放。这样一个简易版的视频播放器就出现了** ##

我们把一个MP4文件拷贝到项目跟目录 命名为ws.mp4  
然后运行源码文件  
看效果图：  
![这里写图片描述][SouthEast 1]

#include <stdio.h>
    
    #define __STDC_CONSTANT_MACROS
    
    #ifdef _WIN32
    //Windows
    extern "C"
    {
    #include "libavcodec/avcodec.h"
    #include "libavformat/avformat.h"
    #include "libswscale/swscale.h"
    #include "SDL2/SDL.h"
    };
    #else
    //Linux...
    #ifdef __cplusplus
    extern "C"
    {
    #endif
    #include <libavcodec/avcodec.h>
    #include <libavformat/avformat.h>
    #include <libswscale/swscale.h>
    #include <SDL2/SDL.h>
    #ifdef __cplusplus
    };
    #endif
    #endif
    
    //Refresh Event
    #define SFM_REFRESH_EVENT  (SDL_USEREVENT + 1)
    
    #define SFM_BREAK_EVENT  (SDL_USEREVENT + 2)
    
    int thread_exit=0;
    int thread_pause=0;
    
    int sfp_refresh_thread(void *opaque){
        thread_exit=0;
        thread_pause=0;
    
        while (!thread_exit) {
            if(!thread_pause){
                SDL_Event event;
                event.type = SFM_REFRESH_EVENT;
                SDL_PushEvent(&event);
            }
            SDL_Delay(40);
        }
        thread_exit=0;
        thread_pause=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[]="ws.mp4";
    
        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);
    
        //Output Info-----------------------------
        printf("---------------- File Information ---------------\n");
        av_dump_format(pFormatCtx,0,filepath,0);
        printf("-------------------------------------------------\n");
    
        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_AUDIO | 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("WS ffmpeg player", SDL_WINDOWPOS_UNDEFINED, SDL_WINDOWPOS_UNDEFINED,
            500, 500,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_KEYDOWN){
                //Pause
                if(event.key.keysym.sym==SDLK_SPACE)
                    thread_pause=!thread_pause;
            }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;
    }

[SouthEast]: /images/20220514/0ebeea435f9c4fb8a22e8ab62fabea3e.png
[http_blog.csdn.net_king1425_article_details_71160339]: http://blog.csdn.net/king1425/article/details/71160339
[SouthEast 1]: /images/20220514/ef2f1474c2e04bc993bd2155235e392e.png