DSP_autocor
4.2 Correlation
DSP_autocor | AutoCorrelation | |||
Function |
| void DSP_autocor(short * restrict r, const short * restrict x, int nx, int nr) |
| |
Arguments |
| r[nr] | Output array | |
|
| x[nx+nr] | Input array. Must be | |
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| nx | Length of autocorrelation. Must be a multiple of 8. | |
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| nr | Number of lags. Must be a multiple of 4. | |
Description |
| This routine accepts an input array of length nx + nr and performs nr | ||
|
| autocorrelations each of length nx producing nr output results. This is typically | ||
|
| used in VSELP code. | ||
Algorithm |
| This is the C equivalent of the assembly code without restrictions. Note that | ||
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| the assembly code is hand optimized and restrictions may apply. | ||
void DSP_autocor(short r[ ],short x[ ], int nx, int nr)
{
int i,k,sum;
for (i = 0; i < nr; i++){ sum = 0;
for (k = nr; k < nx+nr; k++) sum += x[k] * x[k−i];
r[i] = (sum >> 15);
}
}
Special Requirements
-nx must be a multiple of 8.
-nr must be a multiple of 4.
-x[ ] must be
