Forums

Interpolation

Started by cpshah99 March 25, 2008
On Mar 27, 12:02 pm, Randy Yates <ya...@ieee.org> wrote:
> Eric Jacobsen <eric.jacob...@ieee.org> writes: > > [...] > > Actually, it is an interpolator. > > Not according to Lyons, Crochiere and Rabiner, or Mitra.
Because of the etymology of the word "decimate", I would tend to agree more with Eric's opinion here, it's closer to an interpolator than a decimator if new samples must be created that are not equal to any of the old samples. You can get the new samples by using only an interpolation algorithm in any random order without any sequential sample processing. Textbooks don't always use words appropriately, or even consistently in some cases. IMHO. YMMV. -- rhn A.T nicholson d.0.t C-o-M
"Ron N." <rhnlogic@yahoo.com> writes:

> On Mar 27, 12:02 pm, Randy Yates <ya...@ieee.org> wrote: >> Eric Jacobsen <eric.jacob...@ieee.org> writes: >> > [...] >> > Actually, it is an interpolator. >> >> Not according to Lyons, Crochiere and Rabiner, or Mitra. > > Because of the etymology of the word "decimate", I would > tend to agree more with Eric's opinion here, it's closer > to an interpolator than a decimator if new samples must > be created that are not equal to any of the old samples. > You can get the new samples by using only an interpolation > algorithm in any random order without any sequential > sample processing.
As I've already stated, I saw Eric's point in this regard. Yes, I see that you are "interpolating" new samples. But anytime Fso < Fsi, it's called decimation by many in the industry.
> Textbooks don't always use words appropriately, or even consistently > in some cases.
Did you look these references up? Crochiere and Rabiner stand on this definition from page 3. I think you're prematurely dismissing what is standard usage and fairly well-thought-out choices. -- % Randy Yates % "Midnight, on the water... %% Fuquay-Varina, NC % I saw... the ocean's daughter." %%% 919-577-9882 % 'Can't Get It Out Of My Head' %%%% <yates@ieee.org> % *El Dorado*, Electric Light Orchestra http://www.digitalsignallabs.com
>"Ron N." <rhnlogic@yahoo.com> writes: > >> On Mar 27, 12:02 pm, Randy Yates <ya...@ieee.org> wrote: >>> Eric Jacobsen <eric.jacob...@ieee.org> writes: >>> > [...] >>> > Actually, it is an interpolator. >>> >>> Not according to Lyons, Crochiere and Rabiner, or Mitra. >> >> Because of the etymology of the word "decimate", I would >> tend to agree more with Eric's opinion here, it's closer >> to an interpolator than a decimator if new samples must >> be created that are not equal to any of the old samples. >> You can get the new samples by using only an interpolation >> algorithm in any random order without any sequential >> sample processing. > >As I've already stated, I saw Eric's point in this regard. >Yes, I see that you are "interpolating" new samples. But anytime >Fso < Fsi, it's called decimation by many in the industry. > >> Textbooks don't always use words appropriately, or even consistently >> in some cases. > >Did you look these references up? Crochiere and Rabiner stand on this >definition from page 3. I think you're prematurely dismissing what is >standard usage and fairly well-thought-out choices. >-- >% Randy Yates % "Midnight, on the water... >%% Fuquay-Varina, NC % I saw... the ocean's daughter." >%%% 919-577-9882 % 'Can't Get It Out Of My Head' >%%%% <yates@ieee.org> % *El Dorado*, Electric Light Orchestra >http://www.digitalsignallabs.com >
%%%%%% Hello Guys Please help me to understand this concept because I feel it is nice where decimation is updated for every symbol as the weights of the DFE are updated but I am not getting how to do this because in my case the feedforward length is 32 tap (i.e. 32 samples) and feedback filter length is 15 tap (i.e 15 symbol) I have the books by Crochiere and Rabiner and Vaidyanathan. Thank you. Chintan
Randy Yates wrote:

> Did you look these references up? Crochiere and Rabiner stand on this > definition from page 3. I think you're prematurely dismissing what is > standard usage and fairly well-thought-out choices.
Randy, you provided 3 references with this definition, how many others don't use it? I mean, if 3 out 4 use it, it might be OK, but if 3 out of 20 use it, then it is not really a standard. bye, -- piergiorgio
On Mar 27, 3:10 pm, "cpshah99" <cpsha...@rediffmail.com> wrote:

> > Hello Guys > > Please help me to understand this concept because I feel it is nice where > decimation is updated for every symbol as the weights of the DFE are > updated but I am not getting how to do this because in my case the > feedforward length is 32 tap (i.e. 32 samples) and feedback filter length > is 15 tap (i.e 15 symbol) > > I have the books by Crochiere and Rabiner and Vaidyanathan. > > Thank you. > > Chintan
I'm not sure I understand just what you are looking for, but... If you are interested in implementing a standalone adjustable resampling function as one of your blocks, consider the Farrow structure. You can find a description by fred harris here: http://www.signumconcepts.com/download/paper018.pdf Altera provides a detailed description of an implementation here: http://www.altera.com/literature/an/an347.pdf I hope that helps. Never mind the noise level here. In this neighborhood we really, really like to armchair philosophize and language lawyer. We do hear your questions though, even if we don't always understand them. Dale B. Dalrymple
Piergiorgio Sartor
<piergiorgio.sartor.this.should.not.be.used@nexgo.REMOVETHIS.de> writes:

> Randy Yates wrote: > >> Did you look these references up? Crochiere and Rabiner stand on this >> definition from page 3. I think you're prematurely dismissing what is >> standard usage and fairly well-thought-out choices. > > Randy, you provided 3 references with this definition, > how many others don't use it? > > I mean, if 3 out 4 use it, it might be OK, but if 3 out > of 20 use it, then it is not really a standard.
You know, I don't give a damn what you people want to call it. I've seen three extremely respectable and authoritative authors call it that and that's good enough for me. If you want a pissing contest partner on this, look elsewhere. -- % Randy Yates % "The dreamer, the unwoken fool - %% Fuquay-Varina, NC % in dreams, no pain will kiss the brow..." %%% 919-577-9882 % %%%% <yates@ieee.org> % 'Eldorado Overture', *Eldorado*, ELO http://www.digitalsignallabs.com
On Mar 27, 2:56 pm, Randy Yates <ya...@ieee.org> wrote:

>... > >> Not according to Lyons, Crochiere and Rabiner, or Mitra. > ...
> > Did you look these references up? Crochiere and Rabiner stand on this > definition from page 3. I think you're prematurely dismissing what is > standard usage and fairly well-thought-out choices. > -- > % Randy Yates % "Midnight, on the water...
Randy As I quoted above, you have misrepresented Lyons on the topic. I think there is another well thought out approach that avoids the mismatched abstractions in "interpolate" and "decimate". In "Multirate Signal Processing for Communication Systems" fred harris titles Chapter 2 "The Resampling Process". Later on in the chapter "up sampling" and "down sampling" are introduced. The presentation is soundly based on the overwhelmingly common elements of up and down sampling. It postpones the use of the term "interpolation" until an unambiguous basis for understanding and expressing concepts relating to resampling have been established. It avoids the present contention caused by sloppy usage. (But what fun would that be on comp.dsp? :) Dale B. Dalrymple
dbd <dbd@ieee.org> writes:

> On Mar 27, 2:56 pm, Randy Yates <ya...@ieee.org> wrote: > >>... >> >> Not according to Lyons, Crochiere and Rabiner, or Mitra. >> ... > >> >> Did you look these references up? Crochiere and Rabiner stand on this >> definition from page 3. I think you're prematurely dismissing what is >> standard usage and fairly well-thought-out choices. >> -- >> % Randy Yates % "Midnight, on the water... > > Randy > > As I quoted above, you have misrepresented Lyons on the topic.
Actually, I did make an error in interpreting the Lyons text. But it's not the error you state. Further, on closer reading of both Rick's book and your assertions, your interpretation isn't quite right either. My error came from reading the following sentences in section 10.1 beginning on p.382: Sampling rate changes come in two flavors: rate decreases and rate increases. Decreasing the sampling rate is known as decimation. [...] When the sampling rate is being increased, the process is known as interpolation, i.e., estimating intermediate sample values. With just a little more reading (I'm embarrassed to admit it's in the very same paragraph), we find that Rick's definitions only hold for integer values of interpolation or decimation, not fractional values. However, your intimation that Rick would call downsampling by a fractional amount "interpolation" is not supported by anything I could find in this section. He does go into "combining decimation and interpolation" in section 10.3, which is of course what the OP requires. Note that there are no such errors of interpretation of the other two sources. -- % Randy Yates % "Remember the good old 1980's, when %% Fuquay-Varina, NC % things were so uncomplicated?" %%% 919-577-9882 % 'Ticket To The Moon' %%%% <yates@ieee.org> % *Time*, Electric Light Orchestra http://www.digitalsignallabs.com
Chintan,

       First I think your problem needs to be understood well to solve
       it.

       I can help you with understanding and implementation aspects of
       your problem, specially since I have good amount of understanding
       of decimation and interpolation.

       In case if you are in Bangalore, you can come down to my office
       and we can discuss and try and come up with a solution.

       My office address and driving directions are given on our website
       www.arithos.com

       you can also email me at bharat at arithos dot com

Regards
Bharat

On Mar 27, 6:06 pm, Randy Yates <ya...@ieee.org> wrote:

> With just a little more reading (I'm embarrassed to admit it's in the > very same paragraph), we find that Rick's definitions only hold for > integer values of interpolation or decimation, not fractional values. > > However, your intimation that Rick would call downsampling by a > fractional amount "interpolation" is not supported by anything I could > find in this section. He does go into "combining decimation and > interpolation" in section 10.3, which is of course what the OP requires.
I cited p387 of section 10.2 titled "Interpolation" where, amazingly enough, he defines interpolation with no reference to upsampling, downsampling or decimation which was my point. "Decimation" and "interpolation" are not complementary sets spanning sample rate changes and it is sloppy to use them that way. I made no representation of what Lyons would call "downsampling by a fractional amount", I repeated his definition so everyone could make their own interpretation. Please don't assume that when I disagree with you it means that I agree with any others who disagree with you.
> > Note that there are no such errors of interpretation of the other two > sources.
If you represent them as well as you represent what I have posted here there is valid reason for doubt.
> -- > % Randy Yates % "Remember the good old 1980's, when
Dale B. Dalrymple