ffplayer之video

// Register all formats and codecs
av_register_all();

if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_TIMER)){
}

	// Open video file
	//这个地方为什么用ic这个简写呢？搞不明白，input context ?
	if(avformat_open_input(&ic, argv[1], NULL, NULL)!=0)
	  return -1; // Couldn't open file

	// Retrieve stream information
	if(avformat_find_stream_info(ic, NULL)<0)
	  return -1; // Couldn't find stream information

	// Dump information about file onto standard error
	av_dump_format(ic, 0, argv[1], 0);

	// Find the first video stream
	videoStream = -1;
	for(i=0; i<ic->nb_streams; i++) {
		if(AVMEDIA_TYPE_VIDEO == ic->streams[i]->codecpar->codec_type) {
			videoStream = i;
			break;
		}
	}

	if(videoStream == -1) {
		return -1; // Didn't find a video stream
	}

	// Find the decoder for the video stream
	pCodec = avcodec_find_decoder(ic->streams[videoStream]->codecpar->codec_id);
	if(pCodec == NULL) {
		fprintf(stderr, "Unsupported codec!\n");
		return -1; // Codec not found
	}

	AVCodecParameters * pCodecCtxPar = ic->streams[videoStream]->codecpar;

	pCodecCtx = avcodec_alloc_context3(pCodec);

    avcodec_parameters_to_context(pCodecCtx, pCodecCtxPar);

	// Open codec
	if(avcodec_open2(pCodecCtx, pCodec, &optionsDict)<0)
	  return -1; // Could not open codec

	// Allocate video frame
	pFrame = av_frame_alloc();

	AVFrame* pFrameYUV = av_frame_alloc();
	if( pFrameYUV == NULL )
	  return -1;

	screen = SDL_CreateWindow("My Game Window",
				SDL_WINDOWPOS_UNDEFINED,
				SDL_WINDOWPOS_UNDEFINED,
				pCodecCtx->width,  pCodecCtx->height,
				/*SDL_WINDOW_FULLSCREEN |*/ SDL_WINDOW_OPENGL);
	SDL_Renderer *renderer = SDL_CreateRenderer(screen, -1, 0);

	if(!screen) {
		fprintf(stderr, "SDL: could not set video mode - exiting\n");
		exit(1);
	}


	bmp = SDL_CreateTexture(
			renderer,
			SDL_PIXELFORMAT_YV12,
			SDL_TEXTUREACCESS_STREAMING,
			pCodecCtx->width,
			pCodecCtx->height);

	sws_ctx = sws_getContext(
			pCodecCtx->width,
			pCodecCtx->height,
			pCodecCtx->pix_fmt,
			pCodecCtx->width,
			pCodecCtx->height,
			AV_PIX_FMT_YUV420P,
			SWS_BILINEAR,
			NULL,
			NULL,
			NULL);

	int numBytes = av_p_w_picpath_get_buffer_size(AV_PIX_FMT_YUV420P, pCodecCtx->width,
				pCodecCtx->height,1);