Writing from an iPhone, won't be too eloquent... I'd skip using that vDSP function, personally. First, it's single precision. If it's a direct form II transposed implementation, it's probably adequate for most cases (but you're cascading four...possibly noise issues at low frequency settings, I guess still ok). Second, I don't think you're going to see a big performance improvement in a vectored IIR, in typical use cases. So I'd be running a plain-ol' inline IIR with doubles.
The IIR implementation itself is trivial, and very fast as an inline (otherwise the function call overhead is disproportionate, if performance is an issue). Calculating the coefficients takes a little more knowledge, but you can either use my coefficient calculator (for fixed filters), or the C++ code on my site or elsewhere to calc at runtime. Nigel > On Dec 24, 2016, at 5:29 AM, Waverly Edwards <[email protected]> wrote: > > Nigel Redmon wrote: > >>Maybe this will help? Use four biquads, each set to the same frequency, but > >>with Q set as indicated by the calculator: > >>http://www.earlevel.com/main/2016/09/29/cascading-filters/ > > Evan Balster wrote: > >>It took me a while to get my head around digital filter design algorithms. > >>You'll need to do the following steps, which I recommend you research > >>individually: > > Both of these are EXCELLENT resources. I’ve been looking into the cascading > filters options that was suggested and I’ll work on implementing that, if I > understand it correctly. > I will also look into the C++ library that was recommended as well. > > In the process of researching what both of you said, I also found references > to vDSP_biquad. > https://developer.apple.com/reference/accelerate/1450838-vdsp_biquad > It sounds like a great way to go but I just have a very surface level > understanding so implementation will be challenging. > > Thank you both very much, > > > W > > _______________________________________________ > Do not post admin requests to the list. They will be ignored. > Coreaudio-api mailing list ([email protected]) > Help/Unsubscribe/Update your Subscription: > https://lists.apple.com/mailman/options/coreaudio-api/earlevel%40earlevel.com > > This email sent to [email protected]
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