ffmpeg滤镜创建过程

1、创建一个滤镜图

AVFilterGraph *filter_graph = avfilter_graph_alloc();

2、创建滤镜的输入和输出

AVFilterInOut *inputs = avfilter_inout_alloc();

AVFilterInOut *outputs = avfilter_inout_alloc();

3、每个滤镜创建上下文

AVFilterContext *filter1_ctx = avfilter_graph_alloc_filter(filter_graph, filter1, "filter1");

AVFilterContext *filter2_ctx = avfilter_graph_alloc_filter(filter_graph, filter2, "filter2");

4、设置滤镜参数

snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", codecContext->width, codecContext->height, codecContext->pix_fmt, codecContext->time_base.num, codecContext->time_base.den, codecContext->sample_aspect_ratio.num, codecContext->sample_aspect_ratio.den);

5、添加输入滤镜

avfilter_graph_create_filter(&buffersrc_ctx, buffersrc, "input", args, nullptr, filter_graph);

6、添加输出滤镜

avfilter_graph_create_filter(&buffersink_ctx, buffersink, "output", nullptr, nullptr, filter_graph);

7、将滤镜的输入和输出与对应的滤镜上下文关联起来

inputs->name = av_strdup("input");

inputs->filter_ctx = filter1_ctx;

inputs->pad_idx = 0;

inputs->next = NULL;

outputs->name = av_strdup("output");

outputs->filter_ctx = filter2_ctx;

outputs->pad_idx = 0;

outputs->next = NULL;

8、解析滤镜描述

avfilter_graph_parse_ptr(filter_graph, filter_descr, &inputs, &outputs, nullptr);

9、连接滤镜链接

avfilter_graph_config(filter_graph, nullptr);

10、清理资源

avfilter_inout_free(&inputs);

avfilter_inout_free(&outputs);

avfilter_graph_free(&filter_graph);