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Cepstrum question

Here are some questions about cepstrum ! 

Let me take a example to illustrate it.

Suppose a speech signal x(n) with length 256, n = 0--255, with fs =
8000, thus the sampling period is 1/fs = 0.0125s.

Let's take FFT tranform with 1024 length, result a symmtrical
spectrum ,also in 1024 length.Then take absolute value and log
computation, get 1024 length sqrt power spectrum in log domain.
Finally taking IFFT transform, result 1024 points symmtrical  cepstrum
c(m), m =0-1023.

1. c(m) must be a even-symmetrical vector,with a length of 1024.  The
independent variable m, which is called quefrency, is in time
sense.Then how to correspond the quefrency with the real time scale?
That is to say, how much is the sampling period of c(m)?

2.Where is the beginning of c(m)? That is to say,which point is its
real head? m = 0, or m = 1024/2 = 512?


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