Taps in digital FIR filter.vi

I'm trying to use the digital fir filter.vi and while most things seem to behave in a reasonable fashion, the number of taps does not. Using the FIR filter help I implemented the vis shown in the help section with the digital FIR filter.vi and the results (magntidue) agree very well with what is asked for in terms of cut-offs and drop off rate. However, given that I'm using a unit impulse function as the input waveform, the output of the filter vi should be the coefficients of the filter. When I graph those, it is immediately apparent that it is using way more coefficients than I asked for. It quickly became apparent that it is completely ignnoring whatever number you put in for # of taps. Now to a certain extent I understand that. In order to get ever sharper cut-offs you should need more and more points. The question is, why is the number of taps an input if it is ignored or am I missing something?
The other somewhat worrying question has to do with the convolution process. If the filter is using a very large number of taps, there should be a massive delay at the start. I don't think I'm seeing that.

Hello Russo,
Your code looks like it is set up effectively. I spoke with our development team about your question regarding the Digital Filter VI. They confirmed that when Topology is FIR by Specification, the VI reads the filter specification and estimates an order. Then, it calls Parks-McClellan VI to design the filter. That is to say, #Taps is actually not used in this case. When Topology is Equi-ripple FIR or Windowed FIR, the #Taps is used for filter design. You can verify it by checking the order which is equal to #Taps - 1 in filter information output.
If you are interested in a more advanced filter design application, I would suggest you consider checking out the LabVIEW Digital Filter Design Toolkit.
Here is a link to an informative article comparing the LabVIEW Development VIs and the Toolkit VIs:
http://www.ni.com/white-paper/4851/en/#toc2
Warm Regards,
Josh

Similar Messages

Design a Filter using the Digital FIR Filter.vi

Hello,
I was working with Digital FIR Filter.vi to create a bandstand filter.
The problem I faced is regarding the FIR Filter Specification, the Frequencies given for the Upper and Lower Pass and Stop band.
For a low pass Filter, the upper Stop Band frequency is set at 0. While the Lower Stop band frequency is set at 200.
And the Lower pass band is set at 100 while the upper pass band is set at 0.
What the lower and upper frequencies actually means? As for a low pass filter, the upper cutoff frequency must be greater than lower.
So plus tell me how does it works and what frequencies should I specify for a Bandstand Filter.
Thanks v.much

Hi,
Have a look at the following example: [LabVIEW Folder]\examples\Digital Filter Design\Floating-Point Filters\Conventional\Classical Filter Design.vi .This example demonstrates how to use the DFD Classical Design VI to design a lowpass, highpass, bandpass, or bandstop filter with classical design methods.
Complete the following steps to use this VI.
1) Run the VI.
2) Change the specifications.
3) Observe the magnitude response and phase response. Notice that the magnitude response approximates the frequency specification and the phase response is nonlinear for IIR filters (Butterworth, Chebyshev, Inverse Chebyshev, and Elliptic).
4) Change the Design Method to view the ripples in the passband and stopband.
5) Observe the filter order that the VI returns automatically.
6) Click the STOP button to stop this VI.
Sev K.
Applications Engineering Specialist | CLA
National Instruments

ADjusting the sampling rate on a FIR filter?

How do I adjust the sampling rate on a digital FIR filter? Thanks in advance.
-David

You should really start a new thread instead of posting to one that is 5 years old.
To answer your question, it depends on your data. I don't use the DFD but with the filter functions in LabVIEW, if you pass a waveform data type to the function, then the waveform data type contains a dt value. So, set the DAQmx Read to return waveform data. If you are using low level filter functions where the input is a 1D DBL array, then the filter has to be configured. With the low level functions in LabVIEW, you use the various coefficients functions that have a sampling frequency input.

What kind of FIR filter in Labview SignalExpress Tektronix Edition?

I am using FIR filter in Labview SignalExpress Tektronix Edition to process signal acquired from the TDS3032B.But i dont know what kind of this filter(Window,least-squares,or equiripple...).Does any one know about this?

Check out some of NIs links:
Virtual Instrumentation Empowers Digital Signal Processing Design
http://zone.ni.com/devzone/cda/tut/p/id/4759
Designing Filters Using the NI LabVIEW Digital Filter Design Toolkit
http://zone.ni.com/devzone/cda/tut/p/id/3237
lots of information about different FIR can be found by searching on google as well.
National Instruments

FIR filter delay for multistage multirate filter

I know that a FIR filter with N taps has a delay of (N -1 ) / 2 samples.
If this filter decimates of a M factor, the decimated signal has a delay of (N - 1) / (2 * M) samples.
I used this approach several times to calculate the exact delay of a FIR filter, when I know the number of taps.
How can I calculate this delay if I design my filter using the vi "DFD NStage MRate Filter Design"?
Vix
In claris non fit interpretatio
Using LV 2013 SP1 on Win 7 64bit
Using LV 8.2.1 on WinXP SP3
Using CVI 2012 SP1 on Win 7 64bit, WinXP and WinXP Embedded
Using CVI 6.0 on Win2k, WinXP and WinXP Embedded

if I'm right, this is what is called "group delay" or "phase delay" of the filter.
Is there a LV function to get this info?
Vix
In claris non fit interpretatio
Using LV 2013 SP1 on Win 7 64bit
Using LV 8.2.1 on WinXP SP3
Using CVI 2012 SP1 on Win 7 64bit, WinXP and WinXP Embedded
Using CVI 6.0 on Win2k, WinXP and WinXP Embedded

NI5922 High Speed Digitizer - Antialiasing digital input filter

Is it possible to acquire a signal with the NI5922 board, without the antialising digital input filter?
My application doesn't require the antialias protection, and It would be useful the avilability of the full Nyquist band.
Thanks for your answers.
Natalino Roberto

There is no way to disable the alias-protection in the 5922. The
cutoff frequency of the digital input filter varies by sample rate, but
the ratio is constant (cutoff freq = .43 * sample rate). If you
need a wider bandwidth, you will need to increase the sample rate- but,
keep in mind that this may decrease your resolution, since the 5922 is
a flexible-resolution digitizer.
You can configure the type of the digital filter. Refer to the
documentation for the NISCOPE_ATTR_FLEX_FIR_ANTIALIAS_FILTER_TYPE
attribute (Vertical:Advanced:Flex FIR Antialias Filter Type in
LabVIEW). You can configure a number of different options for the
5922. However, the option with the highest bandwidth is the
default setting that I discussed above.

Looking fora camcorder that also has an s-video or rca jack input to convert my vhs tapes to digital

looking fora camcorder that also has an s-video or rca jack input to convert my vhs tapes to digital.

Hi ltcps,
Thanks for writing us!
None of Canon's current camcorders include S-Videos, RCA or other auxiliary inputs.
Did this answer your question? Please click the Accept as Solution button so that others may find the answer as well.

How to convert old VHS tapes to digital

I am hoping someone can give me an overview of what kind of equipment/software is necessary to convert VHS tapes into a digital format that could be saved in iMovie. Do I just need the right cables for the VCR or something more complicated? Thanks!

I recommend that you download the free iMovie HD6 for those with iMovie 08 who do not have a prior version of iMovie HD6. You can get it here: http://www.apple.com/support/downloads/imovieHD6.html
And, do this tutorial: http://www.apple.com/support/imovie/tutorial/
It is more capable of creative editing and you have a quite a bit more control over your iMovie with it.
+So, your method worked using just a VCR, a camcorder, and your computer? No special converters?+
Yes, I just used the AV connectors that came with my camcorder to hook the camcorder to the VCR....which was in a combo TV/VCR unit so I could see the footage on my tv, just to make it easier. The AV connector cable has a special prong that fits into the camcorder, and those white/red/yellow prongs at the VCR end. The TV/VCR is a few years old, certainly not anything fancy or new.
I didn't bother with a converter since I just used the camcorder.
My computer and that VCR are not physically close enough to try to import directly, and since I wanted the digital tapes of the original footage, recording first to the miniDV tapes worked for me. Canopus makes a couple of nice converters...they are around $150-250, I think.
Then, to connect to the computer with the camcorder you will need a 4-6 pin Firewire cable.
+I might do it sooner or I might put it off for awhile while I practice messing around with iMovie.+
The benefit of recording from VHS to miniDV tapes is that the tapes are digital, they store easily and the footage will not degrade before you get around to creating your iMovies and DVDs. iMovies can take up lots of drive space, so don't be thinking that you will just import them all and save them for editing later. You would need a huge amount of space for this. Most of my movies are just under 2 hours, and occupy between 25-40 GB each. A couple of my movies were well over 100-140GB!!!! Yes, that is correct. I have a couple of external drives that I use for my movies while I am creating them. I usually have about two or three that I am working on at the same time.
+We want to put them in a digital format that will be easier to store and play and safer from eroding over time, so I guess the end format I'm looking for is DVDs.+
Because DVDs can break/crack/warp/melt/etc, you should consider exporting your finished iMovies back to the camcorder so that you have the miniDV tapes for more permanent storage and as a backup to your DVDs.
That is one of the big reasons that I don't use iMovie 08---it does not permit exporting back to a camcorder.
Although I do not save my created iMovies on my computer after I have made the DVD and exported the edited movie back to tape, I do save all my iDVD projects as disk images. A disk image can be up to 4.7 GB--even my large movies were automatically compressed down when put into iDVD. The limitation in iDVD is the total length of the movie in TIME, not SIZE. I use single-layer DVDs, which can hold up to 2 hours of content. Creating disk images allows you to have an exact copy of your iDVD projects, self-contained so that you can delete the original iMovies and the original iDVD projects. You can use the disk image to burn your disks when you first create them, and any time in the future. It is a good backup for the entire DVD.
Enjoy being creative with your movie projects! Post back with any more questions, and feel free to email me if you want.
Regards,
Beverly

Any way to use standard VHS deck to convert VHS tape to digital file (iMac)

I use FCE/iMovie. I've had old 8mm films converted to digital files to make family movies - very costly. Is there a way to use a standard VHS deck as a source with my newer iMac to convert old VHS tapes to digital files for editing?

I purhcased the Canopus 55 - it is working well. You can't preview in iMovie, though, which is a challenge and was a comment in reviews on Canopus 55. I did buy the power source with it based on reviews.
However, I am posting a question about iMovie 08 which has quit making thumbnails & writing the video even though the import screen appears to import.

I just switch from tape to digital. The video has a little bounce when played on tv. I copyied the DVD to a folder

I just switch from tape to digital. The video has a little bounce when played on tv. I copyied the DVD to a folder, and burned it to a dvd.
I can see in bounce at the bottom of the screen.

David
Premiere Elements 11, 12, or 13 on Windows 7, 8, or 8.1 64 bit....
You could go back to the project and, in the Edit area, scale out the bouncing bottom edge. I am assuming that it will be visible there.
Then do another burn to folder, and then take the saved folder's VIDEO_TS to DVD disc with your 3rd party software, presumed ImgBurn.
If you want to scale width and height together, then leave the check mark next to Constrain Proportions in Applied Effects Tab/Applied Effects Palette/Motion Panel expanded. If you want to scale width and height separately, the remove the check mark next to Constrain Proportions in Motion Panel expanded.
Please let us know the results. We might consider the Crop Effect also. (fx Effects/Transform/Crop with edits of it int Applied Effects Tab/Applied Effects Palette/Crop Panel expanded).
Thank you.
ATR

How best to Convert, and edit video tape to digital

I want to convert, and edit VHS and Betamax video tapes to digital. My research indicates that there are a number of ways to achieve this, including:
1. A video recorder with a hard disk and DVR (Which?)
2. The "pass through" feature on a MiniDV camcorder (Discussion Sites)
3. EyeTV 250 Plus (Magazine)
4. Canopus' (ADVC300), which “cleans and stabilises analogue video before conversion so the digital is a higher quality than the original analogue” (Magazine and Discussion Sites)
Some claim that an S-video connection is essential for best results.
Can an expert advise the best solution?

I have a Canopus ADVC-300 that I use when digitizing VHS and Hi8 material.
It works quite well. The included software allows you to adjust the quality of the image as it is being converted.
Connect the tape deck to the ADVC-300 using SVHS cable and an audio RCA cable then firewire between the ADVC-300 and your mac. Turn on everything and launch iMovie to capture the playing video stream.
If you have technical questions regarding iMovie and or iDVD, each has a specific forum here on the Apple Discussions site.
Good luck,
x

Advice on converting analog Hi8mm tapes to digital

Hi,
I am looking for advice on converting some Hi8mm analog video tapes to digital. They are not my tapes but I would still prefer to obtain a good quality transfer. I may do some editing on a few of them in PRE and would like to maintain the ability to edit them in the future.
At present, I've bought a Roxio easyVHStoDVD USB converter which states it can capture in DV-AVI format but doesn't actually appear able to do so. Results so far at capturing have been finicky at best but I'm still working on it but am wary because the format captured is not DV-AVI.
I've read several people here suggesting using an ADS Pyro A/D Firewire converter. Would that be a better, less troublesome route to go? And what other tips does anyone have in doing an A/D conversion?
Thanks,
Paul

The workflow that you outline is good for archiving the material, but not so good for later editing that material. As Paul_LS states, a DVD-video will use MPEG-2 encoding. Material and quality will be forever lost. These DVD's are good for doing a backup of the material on tape, but the best quality will result from editing the Captured DV-AVI Type II material. Get an external HDD, instead, and copy those files over to it for later editing.
If you need to do much correction to the Captured material, especially color and exposure work, you might want to look into the Canopus 300, which allows one to do more at the Caputre stage with regards to color and density. The 100 will do a great job of straight Capture, but all corrections will need to be done in PE later.
For a similar Project, with 34 VHS tapes (all sorts of film rates, EP, LP and SP, I did a quick archival copy to DVD (I used my Panasonic VHS-DVD deck for this), and then did a Capture to DV-AVI Type II for all tapes, logging each with details and notes on what each scene was and where it was located, via Timecode. This was all done, while the Capture was being made, and these notes were invaluable, when it came time to actually do the edits.
Using the DV-AVI Type II files (stored on about 4 2TB external (FireWire 800) hard discs, I then Imported just what I needed to create 17 finished DVD's from the tapes. During the edit, I archived each Project to another set of external HDD's, because I will need to do extensive editing for a finished set of DVD's for the two subjects, whose lives were recorded on those 34 tapes. Again, I kept notes on these files, so I know exactly where every scene is located. I can still go back to the Captures, but as I have doine the color grading, and density correction on the next phase of files, those would be the ones that I'd want to use.
In this Project, the biggest help was my "shot sheet," that contained all details of every shot. It saved me countless hours of searching, just to locate a particular scene. If you need a "shot sheet," let me know, and I'll share a PDF of the one that worked for me.
Good luck,
Hunt

Converting/capturing old analogue tapes to digital

Can someone please outline the options and best way to convert my old tapes to digital. I have a new digital video camera and no longer use the old 8mm camera so I would like to convert the old video to digital so I can edit it and generally maintain it all in the same format, we never get to watch the old stuff. I asssume I can't use the digital camera unless it has a video-in port. Otherwise there seems to be a wide range of USB analgue to digital video converters on the market that are fairly inexpensive...do they work?
Thanks...any advice would be appreciated.

I am using the EyeTV Hybrid from ElGato. It works great for VHS. It should work for you too if your analog camcorder has either RCA jacks out (red, white, yellow) or coax cable out.
You first capture the video from analog to Mpeg2 using the EyeTV hybrid. Then you export from EyeTV in DV format so that iMovie can edit it.

Problem converting cassette tape to digital

Hi. I’m looking to convert a cassette tape to digital using my iMac, a Walkman, a male/male 3.5mm-plug cable, and Audacity. I hooked the cable up to the iMac’s line in / mic jack and the Walkman’s headphone jack, set Audacity’s input to “Built-in Input” and hit “Play” on the Walkman. Nothing.
I know the Walkman is working because I can hear the sound through headphones. I went through these troubleshooting steps:
1. Tested the iMac’s line in / mic jack with a microphone. Good signal.
2. Opened System Preferences, Sound, set the input to “Line In” and played the Walkman. No signal picked up there, either, so the problem doesn’t seem to be the settings in Audacity.
3. Tried everything using my iPhone instead of the Walkman. No signal picked up, so the problem doesn’t seem to be with the Walkman.
Other than a bad cable (it worked last time I used it, less than a year ago), anyone have any ideas about what could be going wrong?
Thanks.

Never mind -- problem solved. All I had to do was turn up the volume on the Walkman. It never occured to me that it could be too low, since it was at a comfortable level when listening with earbuds. But that was it.

USRP Frequency Translating FIR Filter

Hi,
I would like to use the USRP as a Software Defined Radio where I can sample a wide spectrum (like 20MHz) and then chose to demodulate a small part of the received spectrum. An example is to sample the whole FM radio band from 88MHz to 108MHz and then from these data FM demodulate 200kHz from a station on 103.9MHz or any other selected signal.
With GNU radio I believe this can be performed by a function called Frequency Xlating FIR Filter which can transform the zero frequency of the IQ data, add a FIR filter and then decimate the data. With LabView I have tried several filters, decimations and transformations but I never end up getting a good output.
Can anyone guide me in the right way on how I can do this?
With regards,
-Sigurd A.

Hi,
I forgot to update this post. I did not find any VI which did this but after some studying and trials I found something that seems to work OK for me. See attached picture.
The clue was to multiply the IQ data with a sinus signal with frequency equal to the frequency shift, and with same sample rate and number of samples as the IQ signal.
Then the signals can be decimated to the wanted bandwidth.
With regards,
Sigurd A.
Attachments:
image.jpg ‏176 KB

Taps in digital FIR filter.vi

Similar Messages

Maybe you are looking for