ffmpeg 视频使用滤镜

ffmpeg 中滤镜的实现其实并不高明，但是功能强大，先给出过滤镜的代码，再翻译我认为有的玩的滤镜。

一帧通过滤镜的函数：

int Filter_One_Frame(FilterArgs *filter_args,AVFrame *frame, AVFrame *filt_frame,const char * filter_descr)
{
    int ret;
    avcodec_register_all();
    av_register_all();
    avfilter_register_all();//注册，假如没有调用会报出不能创建滤镜链

    if (filter_args == NULL || filter_descr == NULL ||frame == NULL ||filt_frame == NULL )
    {    
        printf("%s\nLine %d:%s : input_mp4 == NULL or filter_descr == NULL\n", __FILE__, __LINE__,__func__);
         goto end;
    }
    if ((ret = init_filters(filter_descr,filter_args)) < 0)//初始化滤镜链
        goto end;

        frame->pts = av_frame_get_best_effort_timestamp(frame);        
        /* push the decoded frame into the filtergraph */
        if (av_buffersrc_add_frame(buffersrc_ctx, frame) < 0)
    {
                av_log(NULL, AV_LOG_ERROR, "Error while feeding the filtergraph\n");
            goto end;
    }
        /* pull filtered pictures from the filtergraph */
     while (1)
    {
                ret = av_buffersink_get_frame(buffersink_ctx, filt_frame);//过滤镜
                if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
                    break;
                if (ret < 0)
                    goto end;        
       }
     ret = 0;
end:

    if (filter_graph != NULL)
        avfilter_graph_free(&filter_graph);//释放
    if (ret < 0 && ret != AVERROR_EOF) {
        char buf[1024];
        av_strerror(ret, buf, sizeof(buf));
        fprintf(stderr, "Error occurred: %s\n", buf);
        return -1;
    }
        return 0;
}

FilterArgs 一个结构体：

typedef struct Filter_Args
{
    int width;
    int height;
     enum AVPixelFormat pix_fmt;
    AVRational time_base;
    AVRational sample_aspect_ratio;
}FilterArgs;

这些参数在创建滤镜得时候比较重要，假如和过滤镜得帧不符和，或者参数不合法会导致通过滤镜失败。假如帧的yuv不是从视频中解码出来，也就是没有time_base 和sample_aspect_ratio，那么我一般会设置成{1,20};

函数init_filters:

int init_filters(const char *filters_descr,FilterArgs *filter_args)

{

	char args[512];

	int ret = 0;

	AVFilter *buffersrc  = avfilter_get_by_name("buffer");
	AVFilter *buffersink = avfilter_get_by_name("buffersink");
	AVFilterInOut *outputs = avfilter_inout_alloc();
	AVFilterInOut *inputs  = avfilter_inout_alloc();

	enum AVPixelFormat pix_fmts[] = {AV_PIX_FMT_YUV420P, AV_PIX_FMT_NONE };//modify by elesos.com ?OEAE????oe??????
	if (filters_descr == NULL )
	{	
		printf("%s\nLine %d:%s : filter_args == NULL or filter_descr == NULL\n", __FILE__, __LINE__,__func__);
		 goto end;
	}
	filter_graph = avfilter_graph_alloc();
	if (!outputs || !inputs || !filter_graph )
	{
	    ret = AVERROR(ENOMEM);
	    goto end;
	}
    /* buffer video source: the decoded frames from the decoder will be inserted here. */
	if (filter_args)
	{
		  snprintf(args, sizeof(args),
		            "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
		            filter_args->width, filter_args->height, filter_args->pix_fmt,
		            filter_args->time_base.num, filter_args->time_base.den,
		            filter_args->sample_aspect_ratio.num, filter_args->sample_aspect_ratio.den);
	}
	else
	{
		  snprintf(args, sizeof(args),
		            "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d",
		            pCodecCtx->width, pCodecCtx->height, pCodecCtx->pix_fmt,
		            pCodecCtx->time_base.num, pCodecCtx->time_base.den,
		            pCodecCtx->sample_aspect_ratio.num, pCodecCtx->sample_aspect_ratio.den);
	}
	puts(args);
	ret = avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "in",

	                                   args, NULL, filter_graph);
	if (ret < 0) {

	    av_log(NULL, AV_LOG_ERROR, "Cannot create buffer source\n");

	    goto end;

	}
	 /* buffer video sink: to terminate the filter chain. */
	ret = avfilter_graph_create_filter(&buffersink_ctx, buffersink, "out",
	                                 NULL, NULL, filter_graph);
	if (ret < 0) {
	    av_log(NULL, AV_LOG_ERROR, "Cannot create buffer sink\n");
	    goto end;

	}
	ret = av_opt_set_int_list(buffersink_ctx, "pix_fmts", pix_fmts,AV_PIX_FMT_NONE, AV_OPT_SEARCH_CHILDREN);
	if (ret < 0) {
	    av_log(NULL, AV_LOG_ERROR, "Cannot set output pixel format\n");
	    goto end;
	}

	/* 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;

	if ((ret = avfilter_graph_parse_ptr(filter_graph, filters_descr,&inputs, &outputs, NULL)) < 0)
	  		  goto end;

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

	    goto end;
	end:
	avfilter_inout_free(&inputs);
	avfilter_inout_free(&outputs);
	return ret;

}

下篇给出我尝试过的滤镜及其效果：http://blog.csdn.net/dangxw_/article/details/49001413