On Friday, January 7, 2011 2:42:19 AM UTC-5, hamkanen wrote:
> Hi, Jason, Rick and Jerry, thanks for your responses

You're welcome.

> Since the task is resampling, so i'll need output to be same shape with
> input signal. Because there are "beginning" and "ending" transient response
> , so i think to remove it. So, here is my scheme

Be careful: there's as subtle problem here. The start and end transients are _each_ as long as the FIR filter. If you remove both, the signal that remains will be shorter than the original by as much as the entire filter output is longer. One way or another, you must deal with that.

> i try one period of sinusoidal as input signal
> 
> 1. Upsampling by 3 , (number of array = 2 x 3000 = 6000)
> 2. Filtering (with conv()) with 73-taps filter (number of array = 6000 + 72
> = 6072)
> 3. Remove 36 sample in the beginning and ending --> 6072 - 36 -36 =6000 
> 4. Downsampling by 2 (number of array = 6000 : 2 = 3000)
> 
> the output has same shape with input signal with sample rate changing. Is
> the transient in beginning and the ending, always half of number of FIR
> coeefficient?

Not half, the whole number. The transient arises because the filter's delay line is only partly full.

Jerry