增加一个控制FFT频繁程度的参数 frame_span ，以解决在高采样率下，FFT用于频谱显示来不及处理的问题。

解决该问题终极手段是多线程，但多线程显著增加了复杂性，让代码用于教学不再合适。因此，通过简单的设置间隔来变相解决该问题。

modules/transforms/transform_fft/function_info.cpp

@@ -24,9 +24,16 @@ const char * g_info = "{\n\
 			   \"tooltip\":\"0=Real,1=Complex\",\n\
 			   \"default\":0\n\
 			},\n\
-			\"mod:\":{\n\
+            \"frame_span\":{\n\
                \"type\":\"int\",\n\
-			   \"tooltip\":\"0=frame,1=continous\",\n\
+               \"tooltip\":\"Frame Span (count) between each fft calc. Slower CPU need larger spans.\",\n\
+                \"range\":\">=1\",\n\
+               \"default\":16\n\
+            },\n\
+            \"mod\":{\n\
+			   \"type\":\"int\",\n\
+               \"tooltip\":\"WorkingMod\",\n\
+                \"range\":\"0=Frame,1=Continous\",\n\
 			   \"default\":0\n\
 			},\n\
             \"fftsize\":{\n\

modules/transforms/transform_fft/main.cpp

@@ -76,6 +76,7 @@ int do_fftw(const cmdlineParser & args)
     unsigned int itmstamp_in  = args.toUInt("tmstamp_in",0);
 	unsigned int itmstamp_out = args.toUInt("tmstamp_out",0);
     unsigned int itypes = args.toUInt("input_type",0);//0=real,1=complex
+    const unsigned int frame_span		  = args.toInt("frame_span",1)>0?args.toInt("frame_span",1):1;
     //工作模式
     const int sptype	=	args.toInt("sptype",0);					fprintf(stderr,"sptype is %d.",sptype);
 
@@ -90,7 +91,6 @@ int do_fftw(const cmdlineParser & args)
 		fprintf(stderr,"fftsize must >16.");
 		return res;
 	}
-
     fflush(stderr);
 
 	try{
@@ -150,6 +150,9 @@ int do_fftw(const cmdlineParser & args)
 					}
                 }
 
+                if (map_tmst_inside[header.path_id]++%frame_span)
+                    continue;
+
 				const unsigned char * pdta = packagedta.data();
 				//Normalizer
 				double nmr = fftsize;
@@ -328,7 +331,6 @@ int do_fftw(const cmdlineParser & args)
 					push_subject(FFT,header.path_id,fftsize*sizeof(double)/(itypes==0?2:1),(const unsigned char *)vec_fft_abs.data());
 				if (Spec>0)
 					push_subject(Spec,header.path_id,fftsize*sizeof(double),(const unsigned char *)out);
-				++map_tmst_inside[header.path_id];
 			}
 		}
 
@@ -359,6 +361,8 @@ int do_fftw_continous(const cmdlineParser & args)
 	unsigned int FFT		  = args.toInt("FFT",0);
 	unsigned int Spec		  = args.toInt("Spec",0);
 	unsigned int itmstamp_in  = args.toUInt("tmstamp_in",0);
+    const unsigned int frame_span		  = args.toInt("frame_span",1)>0?args.toInt("frame_span",1):1;
+
 	unsigned int itypes = args.toUInt("input_type",0);//0=real,1=complex
 	//工作模式
 	const int sptype	=	args.toInt("sptype",0);					fprintf(stderr,"sptype is %d.",sptype);
@@ -394,6 +398,7 @@ int do_fftw_continous(const cmdlineParser & args)
 		//Ring buf
 		unordered_map<unsigned int, std::vector<double> > map_buf_inside;
 		unordered_map<unsigned int, long long > map_buf_pos,map_buf_deal;
+        unordered_map<unsigned int, long long > cal_cnt;
 
 		for (int i=0;i<fftsize;++i)
 			vec_fft_abs.push_back(0);
@@ -427,7 +432,10 @@ int do_fftw_continous(const cmdlineParser & args)
 					map_buf_inside[header.path_id]=std::vector<double>(2*RingSize);
 					map_buf_pos[header.path_id] = 0;
 					map_buf_deal[header.path_id] = 0;
+                    cal_cnt[header.path_id] = 0;
 				}
+                if (cal_cnt[header.path_id]++%frame_span)
+                    continue;
 
 				const unsigned char * pdta = packagedta.data();
 				//Normalizer