SkeyeExPlayer(Windows)开发之框架讲解

SkeyeExPlayer for Windows是基于ffmpeg进行开发的全功能播放器，开发过程中参考了很多开源的播放器，诸如vlc和ffplay等，其中最强大的莫过于vlc，但是鉴于vlc框架过于庞大而其中仍存在诸多问题而舍弃了，而其他的更倾向于演示demo，只能提供部分借鉴意义；故而，SkeyeExPlayer 一贯秉承Skeye系列小而精，接口简单功能强大的宗旨从新设计了一套框架，该套框架能适应多线程调用以及多个播放实例同时运行，和SkeyePlayer一样Skeye; 当然，在此也郑重的感谢各大开源播放器以及ffmpeg的作者的无私奉献。

SkeyeExPlayer分为三大模块：打开模块，读取流数据模块，解码模块和渲染模块，其中：

(1) 打开模块

打开流模块很简单，教科书式的调用方法：

代码语言：txt复制

	player->avformat_context = avformat_alloc_context();
	player->avformat_context->interrupt_callback.callback = interrupt_cb;
	player->avformat_context->interrupt_callback.opaque = player;

	// open input file
	AVDictionary *options = NULL;
	//av_dict_set(&options, "rtsp_transport", "udp", 0);
	if (avformat_open_input(&player->avformat_context, url, fmt, &options) != 0) 
	{
		goto error_handler;
	}

	// find stream info
	if (avformat_find_stream_info(player->avformat_context, NULL) < 0) 
	{
		goto error_handler;
	}

	// set current audio & video stream
	for (i=0,idx=-1,cur=-1; i<(int)player->avformat_context->nb_streams; i  ) {
switch (type) {
	case AVMEDIA_TYPE_AUDIO:
		// get last codec context
		if (player->acodec_context) {
			lastctxt = player->acodec_context;
		}

		// get new acodec_context & astream_timebase
		player->acodec_context   = player->avformat_context->streams[idx]->codec;
		player->astream_timebase = player->avformat_context->streams[idx]->time_base;

		// reopen codec
		if (lastctxt) avcodec_close(lastctxt);
		decoder = avcodec_find_decoder(player->acodec_context->codec_id);
		if (decoder && avcodec_open2(player->acodec_context, decoder, NULL) == 0) {
			player->astream_index = idx;
		}
		else {
			av_log(NULL, AV_LOG_WARNING, "failed to find or open decoder for audio !n");
			player->astream_index = -1;
		}
		break;

	case AVMEDIA_TYPE_VIDEO:
		// get last codec context
		if (player->vcodec_context) {
			lastctxt = player->vcodec_context;
		}

		// get new vcodec_context & vstream_timebase
		player->vcodec_context   = player->avformat_context->streams[idx]->codec;
		player->vstream_timebase = player->avformat_context->streams[idx]->time_base;

		// reopen codec
		if (lastctxt) avcodec_close(lastctxt);
		decoder = avcodec_find_decoder(player->vcodec_context->codec_id);
		if (decoder && avcodec_open2(player->vcodec_context, decoder, NULL) == 0) {
			player->vstream_index = idx;
		}
		else {
			av_log(NULL, AV_LOG_WARNING, "failed to find or open decoder for video !n");
			player->vstream_index = -1;
		}
		break;

	case AVMEDIA_TYPE_SUBTITLE:
		return -1; // todo...
		}
	}
	if (idx == -1) return -1;
	// for audio
	if (player->astream_index != -1)
	{
		arate   = player->acodec_context->sample_rate;
		aformat = player->acodec_context->sample_fmt;
		alayout = player->acodec_context->channel_layout;
		//   fix audio channel layout issue
		if (alayout == 0) {
			alayout = av_get_default_channel_layout(player->acodec_context->channels);
		}
		//-- fix audio channel layout issue
	}

	// for video
	if (player->vstream_index != -1) {
		vrate = player->avformat_context->streams[player->vstream_index]->r_frame_rate;
		if (vrate.num / vrate.den >= 100) {
			vrate.num = 25;
			vrate.den = 1;
		}
		player->vcodec_context->pix_fmt = vformat;
		width   = player->vcodec_context->width;
		height  = player->vcodec_context->height;
	}

首先，avformat_open_input打开一个流，为了避免在打开流的时候出现阻塞，我们创建一个线程来执行，同时，为了防止ffmpeg内部出现持久行的阻塞，我们传入阻塞回调函数，在关闭流或者其他必要的时候解除阻塞；avformat_find_stream_info获取流的解码信息，根据音视频以及字幕的解码信息初始化解码器；

(2) 读取流数据模块

代码语言：txt复制

		retv = av_read_frame(player->avformat_context, packet);
		//   play completed   //
		if (retv < 0)
		{
			if (player->avformat_context->pb && player->avformat_context->pb->error)
			{		
				//告知播放实时流中断
				player->error_flag = 1;
				//创建断线重连错误检测线程
				//  [9/4/2017 swordtwelve]
				break;
			}
			player->player_status |= PS_D_PAUSE;
			pktqueue_write_post_i(player->pktqueue, packet);
			usleep(20*1000); 
			continue;
		}
		//-- play completed --//
		player->error_flag = 0;//-1=初始化 0=正常 1-n错误代码

		// audio
		if (packet->stream_index == player->astream_index)
		{
			pktqueue_write_post_a(player->pktqueue, packet);
		}

		// video
		if (packet->stream_index == player->vstream_index)
		{
			pktqueue_write_post_v(player->pktqueue, packet);
		}

		if (  packet->stream_index != player->astream_index
			&& packet->stream_index != player->vstream_index )
		{
			av_packet_unref(packet); // free packet
			pktqueue_write_post_i(player->pktqueue, packet);
		}
	}

读取数据模块超级简单，创建一个线程循环执行av_read_frame，读取到一帧就将其放入队列，这里采用了ffplay的阻塞的方式来处理队列的消费者和生产者的问题，这块有待优化，后续将改成无锁循环队列模式，如SkeyePlayer。

(3) 解码模块

解码模块分为音频和视频解码模块，音视频的解码流程非常相似，

主要分为三步：

a. 从队列中读取音视频编码数据；

b. 音视频分别采用avcodec_decode_audio4和avcodec_decode_video2进行解码；

c. 音视频渲染；

这里着重讲解视频的解码后的过程，其中涉及到解码后的原始图像数据进行处理，解码出一帧图像以后，我们需要对其进行字幕和图像或者其他的视频图像的叠加，借助ffmpeg强大的图像转换和缩放能力，借助VFX库我们很容易实现：

代码语言：txt复制

			consumed = avcodec_decode_video2(player->vcodec_context, vframe, &gotvideo, packet);
			if (consumed < 0) {
				av_log(NULL, AV_LOG_WARNING, "an error occurred during decoding video.n");
				break;
			}

			if (gotvideo) 
			{
				// 解码视频帧添加特技处理 [9/7/2017 dingshuai]
				// 1. 叠加图片
				// 2. 叠加字母
				// 3. 画框...
				// 对解码帧进行特技处理（字符，图片叠加，添加特效） [Dingshuai 2017/08/07]
#if 1
				WaterMarkInfo g_waterMarkInfo = player->vfxConfigInfo.warkMarkInfo;
				if (g_waterMarkInfo.bIsUseWaterMark)
				{
					if (player->vcodec_context->width != vframe->width   || 
						player->vcodec_context->height != vframe->height || 
						player->vfxConfigInfo.warkMarkInfo.bResetWaterMark )
					{
						//初始化水印叠加
						//;表示台标位置：1 == 左上 2 == 右上 3 == 左下 4 == 右下
						//eWaterMarkPos = 3

						//;水印顶点x轴坐标，建议不小于0；不大于视频宽度
						//nLeftTopX = 0

						//;水印顶点y轴坐标，建议不小于0；不大于视频高度
						//nLeftTopY = 480

						//;水印风格：0 - 6
						//eWatermarkStyle = 3

						//;水印图像文件路径LOGO.png
						//strWMFilePath = .Reslogo.png
						switch (g_waterMarkInfo.eWaterMarkPos)
						{
						case POS_LEFT_TOP:
							g_waterMarkInfo.nLeftTopX = 0;
							g_waterMarkInfo.nLeftTopY = 0;
							break;
						case POS_RIGHT_TOP:
							g_waterMarkInfo.nLeftTopX = vframe->width;
							g_waterMarkInfo.nLeftTopY = 0;
							break;
						case POS_LEFT_BOTTOM:
							g_waterMarkInfo.nLeftTopX = 0;
							g_waterMarkInfo.nLeftTopY = vframe->height;
							break;
						case POS_RIGHT_BOTTOM:
							g_waterMarkInfo.nLeftTopX = vframe->width;
							g_waterMarkInfo.nLeftTopY = vframe->height;
							break;
						}

						player->vfxHandle->SetVideoInVideoParam( 101, 0, 0, vframe->width,
							vframe->height, 100, 100, 100);

						player->vfxHandle->SetLogoImage(g_waterMarkInfo.strWMFilePath, g_waterMarkInfo.nLeftTopX,
							g_waterMarkInfo.nLeftTopY, g_waterMarkInfo.bIsUseWaterMark, g_waterMarkInfo.eWatermarkStyle);

						player->vfxConfigInfo.warkMarkInfo.bResetWaterMark = FALSE;
					}
				}


				//初始化字幕信息
				VideoTittleInfo tittleInfo = player->vfxConfigInfo.tittleInfo;
				if(tittleInfo.bResetTittleInfo)
				{

					// 	-->1、初始化创建字幕指针,并初始化视频长宽参数		m_pVideoVfxMakerInfo->nDesWidth, m_pVideoVfxMakerInfo->nDesHeight,  m_pVideoVfxMakerInfo->strDesBytesType);
					player->vfxHandle->CreateOverlayTitle(vframe->width, vframe->height, ("YUY2"));

					// 	-->2、设置字幕文字信息
					LOGFONTA inFont;
					inFont.lfHeight      = tittleInfo.nTittleHeight;
					inFont.lfWidth       = tittleInfo.nTittleWidth;
					inFont.lfEscapement  = 0;
					inFont.lfOrientation = 0;
					inFont.lfWeight      = tittleInfo.nFontWeight;//FW_NORMAL;
					inFont.lfItalic      = 0;
					inFont.lfUnderline   = 0;
					inFont.lfStrikeOut   = 0;
					inFont.lfCharSet        =GB2312_CHARSET;// ANSI_CHARSET;//134
					inFont.lfOutPrecision   =3;// OUT_DEFAULT_PRECIS;
					inFont.lfClipPrecision  = 2;//CLIP_DEFAULT_PRECIS;
					inFont.lfQuality        = 1;//PROOF_QUALITY;
					inFont.lfPitchAndFamily = 0;//49;//49

					strcpy(inFont.lfFaceName, tittleInfo.strFontType);//"华文新魏");//"华文隶书");"隶书"

					POINT pointTitle;

					if(tittleInfo.nMoveType==0)
					{
						pointTitle=	tittleInfo.ptStartPosition;
						if(pointTitle.x<=0) pointTitle.x=1;
						if(pointTitle.x>=vframe->width) pointTitle.x=vframe->width/2;
					}
					else if(tittleInfo.nMoveType==1)//从左往右
					{

						pointTitle.x =	-1;
						pointTitle.y = tittleInfo.ptStartPosition.y;
					}
					else if(tittleInfo.nMoveType==2)
					{
						pointTitle.x =	vframe->width 1;
						pointTitle.y = tittleInfo.ptStartPosition.y;
					}

					player->vfxHandle->SetOverlayTitleInfo(tittleInfo.strTittleContent, 
						inFont, tittleInfo.nColorR, tittleInfo.nColorG,
						tittleInfo.nColorB, pointTitle);

					//-->3、设置字幕运行抓状态
					player->vfxHandle->SetOverlayTitleState(tittleInfo.nState);

					player->vfxConfigInfo.tittleInfo.bResetTittleInfo = FALSE;
				}

				if (player->vfxHandle && (g_waterMarkInfo.bIsUseWaterMark || tittleInfo.nState))//logo-水印   字幕   ？？？
				{
					if (player->vcodec_context->width != vframe->width   || 
						player->vcodec_context->height != vframe->height )
					{
						if (pVfxBuffer)
						{
							free(pVfxBuffer);
							pVfxBuffer = NULL;
						}
					}

					int nBufSize = vframe->width*vframe->height << 1;
					if (!pVfxBuffer)
					{
						pVfxBuffer = (BYTE*)malloc(nBufSize); //缓存写入源数据 
						memset(pVfxBuffer, 0x00, nBufSize);
					}

					AVFrame src;
					av_image_fill_arrays(src.data, src.linesize, pVfxBuffer, outPixelFormat, vframe->width, vframe->height, 1);
					//YUV420 -> YUY2
					ConvertColorSpace(&src, outPixelFormat, vframe, inPixelFormat, vframe->width, vframe->height);
// 					av_image_copy_to_buffer(pVfxBuffer, nBufSize,
// 						vframe->data, vframe->linesize, AV_PIX_FMT_YUYV422,  vframe->width, vframe->height, 1);

					//水印叠加
					if(g_waterMarkInfo.bIsUseWaterMark)
						player->vfxHandle->AddWaterMask(pVfxBuffer);
					//OSD叠加
					if(tittleInfo.nState)
						player->vfxHandle->DoOverlayTitle(pVfxBuffer);

					//YUY2 -> I420
					//ConvertColorSpace(vframe, inPixelFormat, &src, outPixelFormat, vframe->width, vframe->height);
					av_image_fill_arrays(vframe->data, vframe->linesize, pVfxBuffer, outPixelFormat, vframe->width, vframe->height, 1);
					int nPixelFmt = AV_PIX_FMT_YUYV422;
					player_setparam(player, PARAM_RENDER_OUTFORMAT, &nPixelFmt); 
				}
				else
				{
					int nPixelFmt = AV_PIX_FMT_YUV420P;
					player_setparam(player, PARAM_RENDER_OUTFORMAT, &nPixelFmt); 
				}
#endif

由于视频渲染需要一定的时间，我们也将解码帧数据进入队列进行缓存，从而保证播放的流畅性；

(4) 渲染模块

渲染模块分为音频渲染和视频渲染，音频渲染即播放，使用waveOutOpen，waveOutWrite等waveout函数即可实现，下面重点说一下视频渲染，视频渲染通俗讲也就是图像绘制，Windows平台可采用D3D,DDraw, GDI，OpenGL等多种方式进行呈现，本文主要采用3种渲染方式，D3D，GDI和OpenGL；

为了保证渲染的流畅性，我们创建线程执行渲染，

a. 读取解码图像队列；

b. 音视频时间戳同步处理；

c. D3D/gdi/openGL渲染：

ffmpeg 音视频

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