音视频处理FFMPeg开发实战(7) -- Filter的使用(在视频中加入一张图片)

由于在目标视频中有两路视频流合成，与在视频中加入文字稍微有所不同。

1、初始化一个Filter对象：

（1）调用avfilter_graph_alloc()函数创建一个Filter对象
（2）调用函数avfilter_graph_parse2()把描述信息加到Filter对象上。创建一个输入、一个输出 AVFilterInOut对象。
（3）调用avfilter_graph_create_filter创建媒体流输入端的filter;
（4）调用avfilter_graph_create_filter创建图片输入端的filter;
（5）调用avfilter_graph_create_filter创建输出端的filter;
（6）调用avfilter_link()把输入端和输出端连接在一起。
（7）调用avfilter_graph_config（）函数配置filter.。

2、使用Filter对象：

（1）使用av_buffersrc_add_frame_flags（）把解码的帧数据传给Filter。
（2）使用av_buffersink_get_frame（）从Filter中把处理好的数据取出。

3、实例代码：

int AddPictureToVideoStream(string fileInputMediaStream, string pictureFileName, string fileOutput)
{

	// 初始化库，加载编码器
	Init();

	// 打开媒体文件（本地或网络流文件URL）
	if (OpenMediaInputFile(&g_inputMediaStreamContext, (char *)fileInputMediaStream.c_str()) < 0)
	{
		this_thread::sleep_for(chrono::seconds(10));
		return 0;
	}

	// 打开媒体文件（图片）
	if (OpenMediaInputFile(&g_inputPictureContext, (char *)pictureFileName.c_str()) < 0)
	{
		this_thread::sleep_for(chrono::seconds(10));
		return 0;
	}
	// 打开媒体流和图片的解码器
	int ret = InitDecodeCodec();
	if (ret <0)
	{
		this_thread::sleep_for(chrono::seconds(10));
		return 0;
	}

	// 指定输出视频的高宽等各个参数，初始化视频编码器(H.264)
	ret = InitVideoEncoderCodec(g_decoderMediaStreamContext->width, g_decoderMediaStreamContext->height);
	if (ret < 0)
	{
		this_thread::sleep_for(chrono::seconds(10));
		return 0;
	}

	// 初始化过滤器
	InitFilter(g_outputEncContext);
	// Check validity and configure all the links and formats in the graph.
	ret = avfilter_graph_config(g_filter_graph, NULL);
	if (ret < 0)
	{
		return 0;
	}

	// 打开输出媒体文件
	if (OpenOutputMediaFile((char *)fileOutput.c_str()) < 0)
	{
		this_thread::sleep_for(chrono::seconds(10));
		return 0;
	}

	auto pSrcMediaStreamFrame = av_frame_alloc();
	auto pSrcPictureFrame = av_frame_alloc();
	auto  filterFrame = av_frame_alloc();
	auto pInputMediaStreamFrame = av_frame_alloc();
	auto pInputPictureFrame = av_frame_alloc();
	int got_output = 0;
	int64_t  firstPacketTime = 0;
	int64_t outLastTime = av_gettime();
	int64_t inLastTime = av_gettime();

	auto packet_picture = ReadPacketFromPictureInputStream();
	DecodePicturePacket(packet_picture.get(), pSrcPictureFrame);
	firstPacketTime = av_gettime();
	while (true)
	{
		outLastTime = av_gettime();
		auto packet = ReadPacketFromInputMediaStream();
		if (packet)
		{
			
			if (packet->stream_index == 0 && DecodeMediaStreamPacket(packet.get(), pSrcMediaStreamFrame))
			{
				// Set up a new reference to the data described by the source frame.
				// Copy frame properties from src to dst  and 
				// create a new reference for each AVBufferRef from src.
				av_frame_ref(pInputMediaStreamFrame, pSrcMediaStreamFrame);


				// 加一帧媒体流数据到buffer源，
				if (av_buffersrc_add_frame_flags(g_buffersrcMediaStreamContext, pInputMediaStreamFrame, AV_BUFFERSRC_FLAG_PUSH) >= 0)
				{
					pSrcPictureFrame->pts = pSrcMediaStreamFrame->pts;

					// 加一帧图片数据到buffer源，
					if (av_buffersrc_add_frame_flags(g_buffersrcPictureContext, pSrcPictureFrame, AV_BUFFERSRC_FLAG_PUSH) >= 0)
					{
						ret = av_buffersink_get_frame_flags(g_buffersinkContext, filterFrame, AV_BUFFERSINK_FLAG_NO_REQUEST);
						if (ret >= 0)
						{
							std::shared_ptr<AVPacket> pTmpPkt(static_cast<AVPacket*>(av_malloc(sizeof(AVPacket))), [&](AVPacket *p) { av_packet_free(&p); av_freep(&p); });
							av_init_packet(pTmpPkt.get());
							pTmpPkt->data = NULL;
							pTmpPkt->size = 0;

							// 
							// Encode a frame of video.Takes input raw video data from frame and writes the next output packet
							// if available, to avpkt.The output packet does not necessarily contain data for
							// the most recent frame, as encoders can delay and reorder input frames internally as needed.
							// 
							// got_output: set to 1 by libavcodec if the output packet is non - empty, and to 0 if it is
							//			   empty.If the function returns an error, the packet can be assumed to be invalid, and the
							//				value of got_packet_ptr is undefined and should not be used.
							//      
							//  0 on success, negative error code on failure
							ret = avcodec_encode_video2(g_outputEncContext, pTmpPkt.get(), filterFrame, &got_output);
							if (ret >= 0 && got_output)
							{
								int ret = av_write_frame(g_outputContext, pTmpPkt.get());
							}
						}
					}
				}
			}

			av_frame_unref(filterFrame); // 减少帧对象的引用数。复位其中的字段。
			av_frame_unref(pInputMediaStreamFrame);
			av_frame_unref(pSrcMediaStreamFrame);

			// 只输出10秒的数据。
			if ((outLastTime - firstPacketTime) > (10 * 1000 * 1000))
			{
				break;
			}
		}
		else break;
	}

	av_frame_free(&pInputMediaStreamFrame);
	av_frame_free(&pSrcPictureFrame);
	av_frame_free(&filterFrame);
	
	if(g_outputs)
		avfilter_inout_free(&g_outputs);
	if(g_inputs)
		avfilter_inout_free(&g_inputs);

	avfilter_graph_free(&g_filter_graph);
	av_write_trailer(g_outputContext);// 将还未输出的AVPacket输出出来。输出文件尾。

	this_thread::sleep_for(chrono::seconds(2));
	CloseInputContext();
	CloseOutputContext();
	return 0;
}

4、工程项目源文件下载：

在Debug – x86下编译运行。
项目下自带开发环境。

开载源文件