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TOPIC: Re: Method of FIR filter development

Method of FIR filter development 10 years 3 months ago #338

  • Mpoes
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I know you have mentioned offering an FIR plugin at some point, but that it would require advanced knowledge to utilize. Since the primary purpose of FIR for most will be impulse response correct (ie linear phase response), would it be possible to create a system that could integrate with many of the softwares capable of doing this for us.
Phase Arbitrator For instance this software is capable of creating a correction file from an impulse response, which would turn a speaker into a linear phase speaker.

Your DSP device with just this function could be utilized with normal passive speakers, creating a linear phase response from the speaker, and offering a type of correction currently not readily available to most speakers. Most people in the DSP world seem to agree that, when it comes to speaker crossovers, a hybrid approach between IIR and FIR makes far more sense. If you do offer the FIR option, I would also encourage you to handle it this way. FIR filters below say 300hz become too big and processor heavy, as well as having too high a latency. The FIR filters above that are more reasonable, but again, ripple is a common issue. Instead, if 2 IIR filters and 1 FIR filter could be implemented (as a minimum), you would have a very useful and unique device for speaker design.


That particular software is designed for computer use with a convolver and is based around ASIO or VST interfaces, so I don't believe it could be made to communicate with your DSP very easily. However, possibly by talking with the company, or developing your own, we could have very good results. There are numerous FIR development tools out there, including some directly from TI. One that would let you import an impulse response and create a correction from there would be very useful.
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Re:Method of FIR filter development 10 years 3 months ago #340

  • devteam
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Hello,

Very good of you to bring this topic to the table since it's something that we're going to have to worry about in the next few weeks to come! :-)

FIR powered plug-in is indeed on the timeline, but to be honest, we haven't had a chance yet to look at its implementation challenges, already being very busy with other tasks. Your main point of not trying to re-invent the wheel and leveraging existing package is dead on. We're definitely planning to try to become as compatible as possible with other packages, who already perform these.

The IIR + FIR approach is indeed the path we were planning on taking for the same reasons as highlighted in your thread. How we would have these 3rd party software feed data that is compatible (in a table format maybe) with our plug-ins is more where the question comes in. The communication and control with our DSP is not something we want to get into because that would involve a lot of time (investment) to communicate with 3rd party programmers on how to control our board. We don't have the time and energy to go that path, besides the fact that it would open another can of worms with having to support new software platforms.
However, the copy and paste or "Export to miniDSP compatible format" or "export to text file" which our software could easily parse is something that 1) can easily be implemented 2) will still give our software control of our platform, therefore more easily manage bug/revision control.

I'll have a look in the next few weeks at suggested platforms to see how that could potentially work. Any other good suggestions like the one you just made are all welcome!

Time to brainstorm! :-)
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Last Edit: 10 years 3 months ago by devteam.
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Re:Method of FIR filter development 9 years 3 months ago #2522

  • diyjb01
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Hi,
As a year has passed since saying FIR is on the timeline, I'm just wondering if there is any update regarding a FIR powered plug-in.

IMHO this would be a pretty major game changer for DIY, and I'll be literally ordering a pile of MiniDSP's if you can do it.

Even a fairly simple FIR implementation with just linear phase brickwall filters would be fantastic, though of course the ability to input custom FIR blocks would be ideal.

Anything to report? Still on the timeline?
Last Edit: 9 years 3 months ago by diyjb01.
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Re: Method of FIR filter development 9 years 3 months ago #2556

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The new 2x8 platform supposedly has enough power for 'some' FIR filtering. I'd like to echo the 1st post here, and suggest it would be great to combine the IIR and FIR approaches. A single stereo FIR filter on the input channels for phase correction of the whole system, with IIR filters for all EQ and XO.



devteam, there's an open source FIR filter generator here: drc-fir.sourceforge.net/

Perhaps it would be possible to use this to generate miniDSP parameters.

Ideally though, you could build on your existing relationship with REW - it would be great to have measurement/XO/EQ/FIR all in one program.
Last Edit: 9 years 3 months ago by fb.
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Re: Method of FIR filter development 9 years 3 months ago #2566

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FIR implementation is indeed something we've considered but the problem being how "DSP resource" hungry FIR filters are... That's the problem we're faced with..

So at this point of time, a FIR based solution would mean very limited taps and removing processing elsewhere...

But there is always another solution... We'll see if that solution works.. It's a work in progress and not something we'll advertise for now though. :-)

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Re: Method of FIR filter development 9 years 2 months ago #2637

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I actually thought my advanced 2.1 plugin could handle FIR filters. I guess i can't? I havent tried it yet, but it would be sad if it can't handle FIR filters. I just need one at 250-300 Hz.

I have read about faselinear IIR filter in the old days. Here is an old discussion

music.columbia.edu/pipermail/music-dsp/1...November/054289.html

I would love to try linear phase, and don't mind if it's IIR or FIR it's the resulat that matters.
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Re: Method of FIR filter development 9 years 2 months ago #2641

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@Kjeldsen,

As you may already know, FIR is different to IIR. What the miniDSP can do using the Advanced plug-in is the ability to input some custom "biquad" filters (IIR). So nothing related to FIR.

An FIR filter capability would imply the ability to input some "tap coefficients" which are typically very memory intensive and therefore not possible with the current processing on the miniDSP.

Hoping this clarifies a bit,

DevTeam.
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