Brian, I think you rushed to judgment...I said "that vDSP function"—not my job to find him another vDSP function, but I did tell him why it might not be best, so the OP could do that himself.
You misunderstood my performance/optimization comments. The purpose of vDSP is clearly optimization, which I noted was not an issue here. The inline comment was an aside, as a comparison to vDSP, but again I noted it only mattered in situations where performance was an issue—not this case. And not that it matters because I pointed him to existing code—clearly I did not expecting him to be coding and debugging such code, as you implied. I also have the bias that I want at least the option of building a Windows version, so the vDSP solution looks especially bad to me for such a trivial thing as a biquad. The OP can pick his poison, but he already said he was looking at the vDSP solution and saying he expected the implementation to be challenging. I don't know if he was referring to the complicated calling convention or not, but it looks confusing to me. ;-) > On Dec 24, 2016, at 2:16 PM, Brian Willoughby <[email protected]> wrote: > > In response to the first complaint, the vDSP_biquadD() function is double > precision. If vDSP_biquad() is inadequate due to its single precision, then > substituting vDSP_biquadD() is rather trivial. > > In response to the second complaint; the OP has already identified as a > novice, so writing and debugging inline code will be much more challenging > than using Apple's tested version. I'm sure there are a few programmers who > can produce a better implementation than Apple, but why worry about > optimization when it's not yet proven to be an issue? At the very least, > start with Apple's vDSP_biquadD() and then benchmark it against inline code. > > Brian Willoughby > > >> On Dec 23, 2016, at 8:49 PM, Nigel Redmon <[email protected]> wrote: >> 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. > > _______________________________________________ > 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] _______________________________________________ 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/archive%40mail-archive.com This email sent to [email protected]
