Uhm, so it’s a little bit confusing.

Another strange problem is that if i put a 0.64 value of interpolation,

and my flow graph is a file souce->fractional interpolator->file sink,

and my source file is 1GB of data, i’m expecting a 1GB*1/0.64 output

filesize. But when i run the graph i get a 800MB of output filesize,

minor than the source file. I cannot undestand this…

Thank you.

From: Marcus D. Leech

Sent: Tuesday, October 18, 2011 7:45 PM

To: [email protected]

Subject: Re: [Discuss-gnuradio] Odd behaviur of “Fractional

Interpolator”

On 18/10/11 01:38 PM, Mattia R. wrote:

I’m using gnuradio-3.3.0 with GRC.

I’ve builded a graph with a Complex cosine (8Ms/s of sample rate and 1

MHz of frequency), the fractional interpolator with 12/8 value for

interpolation and a FFT sink with 12MS/s of sample rate. (throttle block

included).

I’m expecting to see a 1MHz cosine with the FFT, but i see a 2.25MHz

cosine. If i put 8/12 (the inverse) i see the (correct) 1MHz cosine.

Why?

If i use the Rational resampler, with interpolation 12 and decimation

8, i see the correct 1MHz cosine. What’s wrong with fractional

interpolator block?

Discuss-gnuradio mailing list

[email protected]

https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

Because the fractional interpolator takes the *inverse* as the desired

fraction–think of it as a decimation

ratio.

–

Principal Investigator

Shirleys Bay Radio Astronomy Consortium

Sorry, the filesize is my mistake. All okay now. Thank you.

From: Mattia R.

Sent: Tuesday, October 18, 2011 8:12 PM

To: gnu radio

Subject: Fw: [Discuss-gnuradio] Odd behaviur of “Fractional

Interpolator”

Uhm, so it’s a little bit confusing.

Another strange problem is that if i put a 0.64 value of interpolation,

and my flow graph is a file souce->fractional interpolator->file sink,

and my source file is 1GB of data, i’m expecting a 1GB*1/0.64 output

filesize. But when i run the graph i get a 800MB of output filesize,

minor than the source file. I cannot undestand this…

Thank you.

From: Marcus D. Leech

Sent: Tuesday, October 18, 2011 7:45 PM

To: [email protected]

Subject: Re: [Discuss-gnuradio] Odd behaviur of “Fractional

Interpolator”

On 18/10/11 01:38 PM, Mattia R. wrote:

I’m using gnuradio-3.3.0 with GRC.

I’ve builded a graph with a Complex cosine (8Ms/s of sample rate and 1

MHz of frequency), the fractional interpolator with 12/8 value for

interpolation and a FFT sink with 12MS/s of sample rate. (throttle block

included).

I’m expecting to see a 1MHz cosine with the FFT, but i see a 2.25MHz

cosine. If i put 8/12 (the inverse) i see the (correct) 1MHz cosine.

Why?

If i use the Rational resampler, with interpolation 12 and decimation

8, i see the correct 1MHz cosine. What’s wrong with fractional

interpolator block?

Discuss-gnuradio mailing list

[email protected]

https://lists.gnu.org/mailman/listinfo/discuss-gnuradio

Because the fractional interpolator takes the *inverse* as the desired

fraction–think of it as a decimation

ratio.

–

Principal Investigator

Shirleys Bay Radio Astronomy Consortium