能ffmpeg 的请进！

while(av_read_frame(pDlg->pFormatCtx, &pDlg->packet) >= 0) 
	{
		// Is this a packet from the video stream?
		if(pDlg->packet.stream_index == pDlg->videoStream) 
		{
			// Decode video frame
			avcodec_decode_video(pDlg->pCodecCtx, pDlg->pFrame, &pDlg->frameFinished,
				pDlg->packet.data, pDlg->packet.size);

			// Did we get a video frame?
			if(pDlg->frameFinished) 
			{
				AVPicture pict;

				// Convert the image from its native format to RGB

				struct SwsContext *img_convert_ctx;
				img_convert_ctx = sws_getContext(pDlg->pCodecCtx->width,pDlg->pCodecCtx->height, pDlg->pCodecCtx->pix_fmt,
					pDlg->pCodecCtx->width,pDlg->pCodecCtx->height,PIX_FMT_YUVJ420P,SWS_BICUBIC, NULL,NULL,NULL);      
				if(img_convert_ctx == NULL)
				{
					fprintf(stderr, "Cannot initialize the conversion context!\n");
					getchar();
				}

				// 将图片转换为RGB格式
				sws_scale(img_convert_ctx,pDlg->pFrame->data,pDlg->pFrame->linesize,0,
					pDlg->pCodecCtx->height,pict.data,pict.linesize);

				//pDlg->ShowVido(RGBbuf);
				
				Sleep(50);
			}
		}
		// Free the packet that was allocated by av_read_frame
		av_free_packet(&pDlg->packet);
	}