| Signal Processing Toolbox | |
Permute data into bit-reversed order
Syntax
y = bitrevorder(x) [y,i] = bitrevorder(x)
Description
bitrevorder is useful for pre-arranging filter coefficients so that bit-reversed ordering does not have to be performed as part of an FFT or inverse FFT computation. This can improve run-time efficiency for external applications or for Simulink Blockset models. Note that MATLAB fft and ifft process linear input and output.
y = bitrevorder(x)
returns the input data in bit-reversed order in vector or matrix y. The length of x must be an integer power of 2. If x is a matrix, the bit-reversal occurs on the first dimension of x with size greater than 1. y is the same size as x.
[y,i] = bitrevorder(x)
returns the bit-reversed vector or matrix y and the bit-reversed indices i, such that y = x(i). Recall that MATLAB uses 1-based indexing, so the first index of y will be 1, not 0.
The following table shows the numbers 0 through 7, the corresponding bits and the bit-reversed numbers
| Linear Index |
Bits |
Bit- Reversed |
Bit-Reversed Index |
| 0 |
000 |
000 |
0 |
| 1 |
001 |
100 |
4 |
| 2 |
010 |
010 |
2 |
| 3 |
011 |
110 |
6 |
| 4 |
100 |
001 |
1 |
| 5 |
101 |
101 |
5 |
| 6 |
110 |
011 |
3 |
| 7 |
111 |
111 |
7 |
Example
Obtain the bit-reversed ordered output of a vector.
x=[0:7]'; % Create a column vector
[x,bitrevorder(x)]
ans =
0 0
1 4
2 2
3 6
4 1
5 5
6 3
7 7
See Also
| | bilinear | blackman | |