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根据手册中提供的Greater Than 1024-point FFT代码计算2048点FFT,奇偶序列FFT后组合的结果不对,手册中没有提供
CPLX_Mul(twiddle[k], data_odd[k])。
CPLX_Add(data_even[k], twiddle_times_data_odd, SCALE_FLAG);,
CPLX_Subtract(data_even[k], twiddle_times_data_odd, SCALE_FLAG)
这三个函数的代码。请看一下编写的这三个函数有什么问题,CPLX_Mul这个函数中两个int16的数相乘再移位会造成符号位跟着右移,请问有没有正确的代码
Int32 CPLX_Mul(Int32 op1, Int32 op2) { Int16 op1_r, op1_i, op2_r, op2_i; Int32 op1_op2_r, op1_op2_i; Int16 op1_op2_r16, op1_op2_i16; Int32 cplx_prod; // Mask data for real and imag data = (real:imag) op1_r = op1 >> 16; op1_i = op1 & 0x0000FFFF; op2_r = op2 >> 16; op2_i = op2 & 0x0000FFFF; op1_op2_i = (Int32)op1_r*op2_i + (Int32)op1_i*op2_r; op1_op2_r = (Int32)op1_r*op2_r - (Int32)op1_i*op2_i; op1_op2_i16 = (Int16)(op1_op2_i >> 15); op1_op2_r16 = (Int16)(op1_op2_r >> 15); cplx_prod = (((Int32)op1_op2_r16 & 0x0000FFFF)<< 16); cplx_prod = cplx_prod | ((Int32)op1_op2_i16 & 0x0000FFFF); return cplx_prod; } Int32 CPLX_Add(Int32 op1, Int32 op2 , Uint16 scale_flag) { Int16 op1_r, op1_i, op2_r, op2_i; Int32 op1_op2_r, op1_op2_i; Int16 op1_op2_r16, op1_op2_i16; Int32 cplx_prod; // Mask data for real and imag data = (real:imag) op1_r = op1 >> 16; op1_i = op1 & 0x0000FFFF; op2_r = op2 >> 16; op2_i = op2 & 0x0000FFFF; // Yr = 1/2 * (op1_r + op2_r), Yi = 1/2 *(op1_i + op2_i) op1_op2_i = (Int32)op1_i +(Int32)op2_i; op1_op2_r = (Int32)op1_r +(Int32)op2_r; op1_op2_i16 = (Int16)(op1_op2_i >> 1); op1_op2_r16 = (Int16)(op1_op2_r >> 1); cplx_prod = (((Int32)op1_op2_r & 0x0000FFFF)<< 16); cplx_prod = cplx_prod | ((Int32)op1_op2_i & 0x0000FFFF); return cplx_prod; } Int32 CPLX_Subtract(Int32 op1, Int32 op2 , Uint16 scale_flag) { Int16 op1_r, op1_i, op2_r, op2_i; Int32 op1_op2_r, op1_op2_i; Int16 op1_op2_r16, op1_op2_i16; Int32 cplx_prod; // Mask data for real and imag data = (real:imag) op1_r = op1 >> 16; op1_i = op1 & 0x0000FFFF; op2_r = op2 >> 16; op2_i = op2 & 0x0000FFFF; // Yr = 1/2 * (op1_r - op2_r), Yi = 1/2 *(op1_i - op2_i) op1_op2_i = (Int32)op1_i - (Int32)op2_i; op1_op2_r = (Int32)op1_r - (Int32)op2_r; op1_op2_i16 = (Int16)(op1_op2_i >> 1); op1_op2_r16 = (Int16)(op1_op2_r >> 1); cplx_prod = (((Int32)op1_op2_r & 0x0000FFFF)<< 16); cplx_prod = cplx_prod | ((Int32)op1_op2_i & 0x0000FFFF); return cplx_prod; }
关于移位导致2048结果不正确的问题已经解决,通过分离符号位后进行复数乘法运算再进行右移15位得到S16Q15的数据,代码优化程度不高,如有官方代码可否提供下。另外,我现在想实现8192点或者更高点的FFT运算,请问有可以实现的代码吗,方法还是利用1024库函数的方式。有一点疑问:(1)旋转因子是在DSP内计算还是查表的方式,如果是查表的话,感觉比较耗费资源;(2)中间过程计算也比较占用资源,有什么好的方式解决
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