linux下ffmpeg采集音视频设备，

Linux下查看音视频设备

1、视频输入设备：
命令查看：ls /sys/class/video4linux/
执行结果如下：

如果系统存在video4linux文件夹说明已安装过视频驱动，video4linux目录下每个链接文件代表一个视频设备
查看video0下有哪些文件：ls /sys/class/video4linux/video0
执行结果如下：

读取name文件信息：USB 2.0 CAMERA 为video0视频设备的名称

2、音频输入设备：
命令查看音频输入设备：cat /proc/asound/cards

转载下：
https://blog.csdn.net/tang_chuanlin/article/details/86081102
https://www.cnblogs.com/rushoutasia/p/6409639.html

ffmpeg采集音视频设备

1、采集视频设备USB 2.0 CAMERA：

linux: is->filename="/dev/video0"
windows: is->filename="video=USB 2.0 CAMERA"

补充：

通过SDL2.0渲染YUV420p：

int rtp_playinit(){
    avdevice_register_all();
    av_register_all();
#if USED_NETWORK
    avformat_network_init();
#endif
    SDL_SetMainReady();
    if (SDL_Init (SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER))
    {
        av_log(NULL, AV_LOG_FATAL, "Could not initialize SDL - %s\n", SDL_GetError());
#if USED_NETWORK
        avformat_network_deinit();
#endif
        return -1;
    }
    return 0;
}
static int sdl_window_init(rtpVideoState *is){
    int videoWidth=is->video_ctx->width;
    int videoHeight=is->video_ctx->height;
    int access=SDL_TEXTUREACCESS_STREAMING;//SDL_TEXTUREACCESS_STREAMING
    Uint32 format=SDL_PIXELFORMAT_YV12;
    if(is->hwnd==NULL){
        return -1;
    }
    is->sdl_Window=SDL_CreateWindowFrom(is->hwnd);
    if(is->sdl_Window){
        SDL_ShowWindow(is->sdl_Window);
        fprintf(stdout,"SDL_CreateWindow OK\n");
        fflush(stdout);
    }else{
        fprintf(stdout,"SDL_CreateWindow failed\n");
        fflush(stdout);
        return -1;
    }
    is->sdl_Render = SDL_CreateRenderer(is->sdl_Window,-1,0);
    if(is->sdl_Render==NULL){
        fprintf(stdout,"SDL_CreateRenderer: failed\n");
        fflush(stdout);
        return -1;
    }
    is->sdl_Texture = SDL_CreateTexture(is->sdl_Render, format, access,videoWidth,videoHeight);
    if(is->sdl_Texture==NULL){
        fprintf(stdout,"SDL_CreateTexture: failed\n");
        fflush(stdout);
        return -1;
    }
    return 0;
}
static void sdl_window_deinit(rtpVideoState *is){
    if(is->sdl_Texture){
        SDL_DestroyTexture(is->sdl_Texture);
        is->sdl_Texture=NULL;
    }
    if(is->sdl_Render){
        SDL_DestroyRenderer(is->sdl_Render);
        is->sdl_Render=NULL;
    }
    if(is->sdl_Window){
        SDL_DestroyWindow(is->sdl_Window);
        is->sdl_Window=NULL;
    }
}

渲染部分代码：

SDL_UpdateYUVTexture(decoder->sdl_Texture, NULL, pFrameYUV->data[0], pFrameYUV->linesize[0],pFrameYUV->data[1], pFrameYUV->linesize[1],pFrameYUV->data[2], pFrameYUV->linesize[2]);
            // SDL_UpdateTexture(decoder->sdl_Texture, NULL,pFrameYUV->data[0],pFrameYUV->linesize[0]);
            SDL_RenderClear(decoder->sdl_Render);
            SDL_RenderCopy(decoder->sdl_Render,decoder->sdl_Texture, NULL,NULL);
            SDL_RenderPresent(decoder->sdl_Render );

注：SDL_ShowWindow(is->sdl_Window); 缺少这一行，第二次用同句柄初始化将黑屏，画面不出来。

单做下笔记，如有不对请打脸！！！