ffmpeg avfilter 系列一 （水印处理）

ffmpeg avfilter 具有强大的处理功能，如视频水印、Overlay、视频补帧、抠图、音频流重采样等功能，是一个值得深入研究的模块。

其中最简单版本为雷霄骅提供的水印功能（https://blog.csdn.net/leixiaohua1020/article/details/29368911），因为原始的YUV数据没有时间戳的功能，需要手动的添加时间戳，这里进行补充记录下，其过程请参考上面的雷大神的原始链接。

 

 

 

int main(int argc, char *argv[])
{
	int ret;
	AVFrame *frame_in = NULL;
	AVFrame *frame_out = NULL;
	unsigned char *frame_buffer_in = NULL;
	unsigned char *frame_buffer_out = NULL;

	//
	AVFilterContext *buffersink_ctx = NULL;
	AVFilterContext *buffersrc_ctx = NULL;


	AVFilterGraph *filter_graph = NULL;

	static int video_stream_index = -1;

	//Input YUV
	FILE *fp_in = fopen("test.yuv", "rb+");
	if (fp_in == NULL) 
	{
		printf("Error open input file.\n");
		return -1;
	}
	int in_width = 832;
	int in_height = 480;

	//Output YUV
	FILE *fp_out = fopen("output.yuv", "wb+");
	if (fp_out == NULL) 
	{
		printf("Error open output file.\n");
		return -1;
	}


	//过程一：构建Filter Graph

	//步骤1：注册所有filter,后续才能通过 "buffer" 等识别到具体的Filter
	//ffmpeg4.0 不再需要提前注册
	//avfilter_register_all();

	//filter 功能描述
	//const char *filter_descr = "[in]overlay=x='if(gte(t,2), -w+(t-2)*20, NAN)':y=0[out]";
	//const char *filter_descr = "boxblur";
	//const char *filter_descr = "drawtext=fontfile=arial.ttf:fontcolor=red:fontsize=30:text='Lei Xiaohua':x=50:y=50";

	//const char *filter_descr = "scale=300:100[wm];[in][wm]overlay=50:50[out]";

	//const char *filter_descr = "[in]scale=300:100[scl];[in1][scl]overlay=25:25";
	//const char *filter_descr = "scale=832:480,transpose=cclock";

	//scale = 78:24[scl]; [scl] transpose = cclock // assumes "[in]" and "[out]" to be input output pads respectively


	//const char *filter_descr = "crop=iw/2:ih:0:0,split[left][tmp];[tmp]hflip[right]; [left]pad=iw*2[a];[a][right]overlay=w";

	//const char *filter_descr = "movie=test.jpg[wm];[in][wm]overlay=5:5[out]";

	const char *filter_descr = "movie=my_logo.png[wm];[in][wm]overlay=5:5[out]";

	//const char *filter_descr = "drawtext=fontfile = arial.ttf:x = w - tw : fontcolor = white : fontsize = 30 : text = '%{localtime\:%H\\\:%M\\\:%S";
	
	char args[512];

	//定义：特殊的filter：buffer表示filter graph中的输入filter，原始数据就往这个节点输入
	//定义：特殊的filter：buffer sink 表示filter graph中的输出filter，处理后的数据从这个节点输出

	//AVFilter **buffersrc = (AVFilter**)av_malloc( sizeof(AVFilter*));
	const AVFilter *buffersrc = avfilter_get_by_name("buffer");
	const AVFilter *buffersink = avfilter_get_by_name("buffersink");

	//输入输出端口
	AVFilterInOut *outputs = avfilter_inout_alloc();
	AVFilterInOut *inputs = avfilter_inout_alloc();


	enum AVPixelFormat pix_fmts[] = { AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };
	//定义：
	AVBufferSinkParams *buffersink_params;


	//步骤2：开辟内存空间
	filter_graph = avfilter_graph_alloc();

	/* buffer video source: the decoded frames from the decoder will be inserted here. */
	snprintf(args, sizeof(args),
		"video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
		in_width, in_height, AV_PIX_FMT_YUV420P,1, 25, 1, 1);




	ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in", args, NULL, filter_graph);
	if (ret < 0) 
	{
		printf("Cannot create buffer source\n");
		return ret;
	}

	/* buffer video sink: to terminate the filter chain. */
	buffersink_params = av_buffersink_params_alloc();
	buffersink_params->pixel_fmts = pix_fmts; //理论上是指：所支持的视频格式，但源码中，这个参数传进去没有用到

	// 创建一个滤波器实例AVFilterContext，并添加到AVFilterGraph中
	//buffersink_params 貌似没啥用
	ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",NULL, buffersink_params, filter_graph);
	//ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out", NULL, NULL, filter_graph);
	av_free(buffersink_params);
	if (ret < 0) 
	{
		printf("Cannot create buffer sink\n");
		return ret;
	}

	/* Endpoints for the filter graph. */
	outputs->name = av_strdup("in");
	outputs->filter_ctx = buffersrc_ctx;
	outputs->pad_idx = 0;
	outputs->next = NULL;

	inputs->name = av_strdup("out");
	inputs->filter_ctx = buffersink_ctx;
	inputs->pad_idx = 0;
	inputs->next = NULL;


	//将一串通过字符串描述的Graph添加到FilterGraph中
	if ((ret = avfilter_graph_parse_ptr(filter_graph, filter_descr,&inputs, &outputs, NULL)) < 0)
		return ret;

	if ((ret = avfilter_graph_config(filter_graph, NULL)) < 0)
		return ret;


	//过程二：处理数据frame
	frame_in = av_frame_alloc();
	frame_buffer_in = (unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width, in_height, 1));
	av_image_fill_arrays(frame_in->data, frame_in->linesize, frame_buffer_in,AV_PIX_FMT_YUV420P, in_width, in_height, 1);

	frame_out = av_frame_alloc();
	frame_buffer_out = (unsigned char *)av_malloc(av_image_get_buffer_size(AV_PIX_FMT_YUV420P, in_width, in_height, 1));
	av_image_fill_arrays(frame_out->data, frame_out->linesize, frame_buffer_out,AV_PIX_FMT_YUV420P, in_width, in_height, 1);

	frame_in->width = in_width;
	frame_in->height = in_height;
	frame_in->format = AV_PIX_FMT_YUV420P;



	while (1) 
	{
		if (fread(frame_buffer_in, 1, in_width*in_height * 3 / 2, fp_in) != in_width*in_height * 3 / 2)
		{
			break;
		}
		//input Y,U,V
		frame_in->data[0] = frame_buffer_in;
		frame_in->data[1] = frame_buffer_in + in_width*in_height;
		frame_in->data[2] = frame_buffer_in + in_width*in_height * 5 / 4;

		//在使用movie添加水印时需要更新frame的时间戳
		frame_in->pts++;
		frame_in->pts = frame_in->pts * 40;


		// 往源滤波器buffer中输入待处理的数据
		if (av_buffersrc_add_frame(buffersrc_ctx, frame_in) < 0) 
		{
			printf("Error while add frame.\n");
			break;
		}

		// 从目的滤波器buffersink中输出处理完的数据
		ret = av_buffersink_get_frame(buffersink_ctx, frame_out);
		if (ret < 0)
			break;

		//output Y,U,V
		if (frame_out->format == AV_PIX_FMT_YUV420P) 
		{
			for (int i = 0; iheight; i++) 
			{
				fwrite(frame_out->data[0] + frame_out->linesize[0] * i, 1, frame_out->width, fp_out);
			}
			for (int i = 0; iheight / 2; i++) 
			{
				fwrite(frame_out->data[1] + frame_out->linesize[1] * i, 1, frame_out->width / 2, fp_out);
			}
			for (int i = 0; iheight / 2; i++) 
			{
				fwrite(frame_out->data[2] + frame_out->linesize[2] * i, 1, frame_out->width / 2, fp_out);
			}
		}
		printf("Process 1 frame!\n");
		av_frame_unref(frame_out);
	}

	fclose(fp_in);
	fclose(fp_out);

	av_frame_free(&frame_in);
	av_frame_free(&frame_out);
	avfilter_graph_free(&filter_graph);

	return 0;

}