前言

介紹FFmpeg中旋轉rotate、拼接hstack、翻轉hflip、邊緣edgedetect視頻濾鏡的使用方法。

1、 旋轉濾鏡

1.1 名稱：rotate
1.2 語法：-angle:旋轉角度，-ow:輸出圖像寬度，-oh:輸出圖像高度；如："angle=0.5*PI:ow=1920:oh=1080"
1.3 其他：若需要實時旋轉圖像，則需要動態創建和銷毀濾鏡。
1.4 示例代碼

static int initFilter(AVCodecContext * codecContext0, AVCodecContext * codecContext1, double angle) {int ret = 0;const AVFilter *bufSrc = NULL;const AVFilter *rotate = NULL;const AVFilter *bufSink = NULL;AVFilterInOut *input = NULL;AVFilterInOut *output = NULL;char args[128] = {0};if(NULL == filterGraph)filterGraph = avfilter_graph_alloc();else{return true;}input = avfilter_inout_alloc();output = avfilter_inout_alloc();bufSrc = avfilter_get_by_name("buffer");rotate = avfilter_get_by_name("rotate");bufSink = avfilter_get_by_name("buffersink");if(NULL == filterGraph || NULL == input || NULL == output){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "alloc failed! :" << endl;return false;}if(NULL == bufSrc || NULL == bufSink){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_get_by_name failed! :" << endl;return false;}snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", codecContext0->width, codecContext0->height, codecContext0->pix_fmt, 1, 25, 1, 25); // cout << args << endl;// src 0ret = avfilter_graph_create_filter(&bufSrcContext[0], bufSrc, "in0", args, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// rotatesnprintf(args, sizeof(args), "angle=%f*PI:ow=%d:oh=%d", angle/double(180), codecContext0->width+20*16, codecContext0->height+40*16);cout << args << endl;ret = avfilter_graph_create_filter(&rotateContext, rotate, "rotate", args, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// sinkret = avfilter_graph_create_filter(&bufSinkContext, bufSink, "out", NULL, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}ret = avfilter_link(bufSrcContext[0], 0, rotateContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_link(rotateContext, 0, bufSinkContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_graph_config(filterGraph, NULL);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_config failed! :" << buf << endl;return false;}if(input->next) avfilter_inout_free(&input->next);if(input )avfilter_inout_free(&input);if(output) avfilter_inout_free(&output);return true; }

2、 左右拼接濾鏡

2.1 名稱：hstack
2.2 語法：-inputs:輸出源數量；如："inputs=2"
2.3 其他：1）拼接后尺寸會變大，為輸入源尺寸的和，buffer in0 + buffer in1；2）引申：上下拼接濾鏡vstack。
2.4 示例代碼

static int initFilter(AVCodecContext * codecContext0, AVCodecContext * codecContext1) {int ret = 0;const AVFilter *bufSrc = NULL;const AVFilter *hstack = NULL;const AVFilter *bufSink = NULL;AVFilterInOut *input = NULL;AVFilterInOut *output = NULL;char args[128] = {0};if(NULL == filterGraph)filterGraph = avfilter_graph_alloc();else{return true;}input = avfilter_inout_alloc();output = avfilter_inout_alloc();bufSrc = avfilter_get_by_name("buffer");hstack = avfilter_get_by_name("hstack");bufSink = avfilter_get_by_name("buffersink");if(NULL == filterGraph || NULL == input || NULL == output){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "alloc failed! :" << endl;return false;}if(NULL == bufSrc || NULL == bufSink){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_get_by_name failed! :" << endl;return false;}snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", codecContext0->width, codecContext0->height, codecContext0->pix_fmt, 1, 25, 1, 25);cout << args << endl;// src 0ret = avfilter_graph_create_filter(&bufSrcContext[0], bufSrc, "in0", args, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", codecContext0->width, codecContext0->height, codecContext0->pix_fmt, 1, 25, 1, 25);cout << args << endl;// src 1ret = avfilter_graph_create_filter(&bufSrcContext[1], bufSrc, "in1", args, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// hstackret = avfilter_graph_create_filter(&hstackContext, hstack, "hstack", "inputs=2", NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// sinkret = avfilter_graph_create_filter(&bufSinkContext, bufSink, "out", NULL, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}ret = avfilter_link(bufSrcContext[0], 0, hstackContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_link(bufSrcContext[1], 0, hstackContext, 1);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_link(hstackContext, 0, bufSinkContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_graph_config(filterGraph, NULL);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_config failed! :" << buf << endl;return false;}if(input->next) avfilter_inout_free(&input->next);if(input )avfilter_inout_free(&input);if(output) avfilter_inout_free(&output);return true; }

3、水平翻轉濾鏡

3.1 名稱：hflip
3.2 語法：無配置參數
3.3 其他：引申：垂直翻轉濾鏡vflip
3.4 示例代碼

static int initFilter(AVCodecContext * codecContext0, AVCodecContext * codecContext1) {int ret = 0;const AVFilter *bufSrc = NULL;const AVFilter *hflip = NULL;const AVFilter *bufSink = NULL;AVFilterInOut *input = NULL;AVFilterInOut *output = NULL;char args[128] = {0};if(NULL == filterGraph)filterGraph = avfilter_graph_alloc();else{return true;}input = avfilter_inout_alloc();output = avfilter_inout_alloc();bufSrc = avfilter_get_by_name("buffer");hflip = avfilter_get_by_name("hflip");bufSink = avfilter_get_by_name("buffersink");if(NULL == filterGraph || NULL == input || NULL == output){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "alloc failed! :" << endl;return false;}if(NULL == bufSrc || NULL == bufSink){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_get_by_name failed! :" << endl;return false;}snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", codecContext0->width, codecContext0->height, codecContext0->pix_fmt, 1, 25, 1, 25);cout << args << endl;// src 0ret = avfilter_graph_create_filter(&bufSrcContext[0], bufSrc, "in0", args, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// hflipret = avfilter_graph_create_filter(&hflipContext, hflip, "hflip", NULL, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// sinkret = avfilter_graph_create_filter(&bufSinkContext, bufSink, "out", NULL, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}ret = avfilter_link(bufSrcContext[0], 0, hflipContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_link(hflipContext, 0, bufSinkContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_graph_config(filterGraph, NULL);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_config failed! :" << buf << endl;return false;}if(input->next) avfilter_inout_free(&input->next);if(input )avfilter_inout_free(&input);if(output) avfilter_inout_free(&output);return true; }

4、邊緣檢測濾鏡

4.1 名稱：edgedetect
4.2 語法： -low:低閾值；-high:高閾值；必須在[0,1]范圍內選擇低閾值和高閾值，低閾值應小于或等于高閾值。-mode:定義繪圖模式,‘wires’:黑白;‘colormix’:類似油畫效果，卡通效果；默認值為wires。舉例："mode=colormix:low=0.1:high=0.4"
4.3 其他：注意濾鏡輸出格式為GRAY8(wires)、GBR24P(colormix)而非YUV。
4.4 示例代碼

static int initFilter(AVCodecContext * codecContext0, AVCodecContext * codecContext1) {int ret = 0;const AVFilter *bufSrc = NULL;const AVFilter *edgedetect = NULL;const AVFilter *bufSink = NULL;AVFilterInOut *input = NULL;AVFilterInOut *output = NULL;char args[128] = {0};if(NULL == filterGraph)filterGraph = avfilter_graph_alloc();else{return true;}input = avfilter_inout_alloc();output = avfilter_inout_alloc();bufSrc = avfilter_get_by_name("buffer");edgedetect = avfilter_get_by_name("edgedetect");bufSink = avfilter_get_by_name("buffersink");if(NULL == filterGraph || NULL == input || NULL == output){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "alloc failed! :" << endl;return false;}if(NULL == bufSrc || NULL == bufSink){cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_get_by_name failed! :" << endl;return false;}snprintf(args, sizeof(args), "video_size=%dx%d:pix_fmt=%d:time_base=%d/%d:pixel_aspect=%d/%d", codecContext0->width, codecContext0->height, codecContext0->pix_fmt, 1, 25, 1, 25);cout << args << endl;// src 0ret = avfilter_graph_create_filter(&bufSrcContext[0], bufSrc, "in0", args, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// edgedetectret = avfilter_graph_create_filter(&edgedetectContext, edgedetect, "edgedetect", "mode=colormix:low=0.1:high=0.4", NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}// sinkret = avfilter_graph_create_filter(&bufSinkContext, bufSink, "out", NULL, NULL, filterGraph);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_create_filter failed! :" << buf << endl;return false;}ret = avfilter_link(bufSrcContext[0], 0, edgedetectContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_link(edgedetectContext, 0, bufSinkContext, 0);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_link failed! :" << buf << endl;return false;}ret = avfilter_graph_config(filterGraph, NULL);if(0 > ret){char buf[1024] = { 0 };av_strerror(ret, buf, sizeof(buf) - 1);cout << "[" << __FILE__ << "|" << __LINE__ << "]" << "avfilter_graph_config failed! :" << buf << endl;return false;}if(input->next) avfilter_inout_free(&input->next);if(input )avfilter_inout_free(&input);if(output) avfilter_inout_free(&output);return true; }

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