[sdiy] IR Reverb

Tim Ressel timr at circuitabbey.com
Wed Feb 21 00:21:22 CET 2018

Thanks for all the responses!

The 'H7 looks interesting, though expensive. I love how STM sells these 
dev boards basically at cost.

Here is another question. As i get my brain around this, with the small 
FFTs giving way to larger FFTs, I wonder- what format is the IR file? Is 
it just a time-domain recording of the reverberations of a room excited 
by an impulse? Admittedly I am getting lost in all the conversions going 
on. Its like I'm in church!???? ;-)


On 2/20/2018 1:51 PM, Mikko Helin wrote:
> STM32H7 will be killer for DSP with 400 MHz core clock frequency and 1 
> Mb of SRAM:
> http://www.st.com/en/microcontrollers/stm32h7-series.html?querycriteria=productId=SS1951
> There will be (not available yet) NUCLEO-H743ZI??dev board. Would 
> somebody please build a euro format base board with some knobs, jacks 
> and maybe an LCD for that:
> https://www.digikey.fi/product-detail/en/stmicroelectronics/NUCLEO-H743ZI/497-17786-ND/7809236
> On Tue, Feb 20, 2018 at 6:25 PM, Ben Stuyts <ben at stuyts.nl 
> <mailto:ben at stuyts.nl>> wrote:
>     Not only floating point operations, they also have DSP and SIMD
>     instructions. There???s a library of functions (CMSIS-DSP) which
>     makes these operations easy to use.
>     Ben
>>     On 20 Feb 2018, at 14:19, Martin Klang <mars at pingdynasty.com
>>     <mailto:mars at pingdynasty.com>> wrote:
>>     STMs: the F4 and F7 are Cortex M4F with single cycle floating
>>     point operations. Not sure there's much to gain from going fixed
>>     point, assuming 32bits. With 16 bits fixed point you can
>>     potentially get two operations per cycle. Or you could go 8-bit...
>>     Martin
>>     On 18/02/18 19:20, Bruno Afonso wrote:
>>>     If you're willing to go into DSP land then you could also look
>>>     at blackfin, Monome's Aleph uses open source tools for develop
>>>     it. For STMs, the only shot would be to attempt to use fixed
>>>     point, not a lot of juice for floating point stuff but like
>>>     other's mention, it may be a lot of work.. maybe more for as a
>>>     challenge? :)
>>>     b
>>>     On Sat, Feb 17, 2018 at 5:24 AM <rsdio at audiobanshee.com
>>>     <mailto:rsdio at audiobanshee.com>> wrote:
>>>         I haven???t developed for SHARC, yet, but I can say that I
>>>         shipped the Soundplane without spending much on the
>>>         compiler/assembler. That was based on the TMS320VC5506, a
>>>         member of the lowest-power C55x line. You might want to look
>>>         at the C6000 series or OMAP, such as the OMAP-L1x line. I
>>>         recall that the tools run free when you have one of the
>>>         evaluation boards connected to your computer.
>>>         What about some of the less ???fancy" SHARC DSP options, like
>>>         the ADSP-2191M used in the DSI eVoLver? For some reason, I
>>>         assume that a 16-bit DSP would cost less. Dave (and/or his
>>>         firmware programmer) managed to coax 24-bit audio out of
>>>         this 16-bit DSP by using specific features. I haven???t looked
>>>         into the tools for that chip, but maybe they???re priced lower
>>>         than the tools for the flagship chips.
>>>         Brian
>>>         On Feb 16, 2018, at 3:50 PM, Tim Ressel
>>>         <timr at circuitabbey.com <mailto:timr at circuitabbey.com>> wrote:
>>>         > I hear ya. My comment about the cost of tools referred to
>>>         the compilers. I'd love to use a Sharc, but it looks like at
>>>         least $1K for the compiler.
>>>         >
>>>         > --tr
>>>         >
>>>         > On 2/16/2018 1:48 PM, rsdio at audiobanshee.com
>>>         <mailto:rsdio at audiobanshee.com> wrote:
>>>         >> You really need a DSP for this, and not a general-purpose
>>>         CPU like ARM. Even though ARM has a DSP instruction or two,
>>>         it's a far cry from a total system designed for signal
>>>         processing. Families like the TMS320 have been evolving for
>>>         decades - literally 35 years - to optimize this sort of
>>>         thing. Literally every aspect of the chip has been tweaked
>>>         to optimize signal processing.
>>>         >>
>>>         >> Texas Instruments has cheap demo platforms with audio I/O
>>>         and the tools come free with those $50 evaluation boards.
>>>         There are a lot of open-source routines, so if you need FFT
>>>         in TMS320 assembly then it's there. You can call that from C
>>>         and keep your overall design simple.
>>>         >>
>>>         >> Texas Instruments even has chips that are dual-processor
>>>         inside - one TMS320 for DSP, plus and ARM for the higher
>>>         level stuff and maybe even some audio processing. Look for
>>>         OMAP chips. The C6000 series of DSP would be a good choice
>>>         because it supports floating point (I've worked with the
>>>         C5500 series that is fixed point, and that's a lot of tedium
>>>         but worth it if you want to run off of batteries).
>>>         >>
>>>         >> Another good option would be SHARC.
>>>         >>
>>>         >> If you choose a non-DSP chip, everything will be less
>>>         efficient. That either means loss of features or higher
>>>         temperatures and shorter battery life.
>>>         >>
>>>         >> Brian Willoughby
>>>         >> Sound Consulting
>>>         >>
>>>         >> On Feb 16, 2018, at 11:47 AM, Tim Ressel
>>>         <timr at circuitabbey.com <mailto:timr at circuitabbey.com>> wrote:
>>>         >>> I wonder if it would be possible to do a parallel
>>>         processor scheme where one proc handles the early stuff and
>>>         another to handle the longer time stuff. each proc would
>>>         output via a codec and those outputs would get summed. Hmm...
>>>         >>>
>>>         >>> On 2/16/2018 11:38 AM, Eric Brombaugh wrote:
>>>         >>>> I suspect that STM32 doesn't have the horsepower you'll
>>>         need to do a useful IR reverb. There are several fairly
>>>         efficient FFT in the CMSIS libraries from ARM but even using
>>>         those the best you can do is about a 4096 FFT running at
>>>         less than 48kHz with long latency and large overlaps.
>>>         >>>>
>>>         >>>> On 02/16/2018 12:24 PM, Tim Ressel wrote:
>>>         >>>>> Still, even with all that jigery-pokery, we're going
>>>         to need a bigger boat, er, processor. I'd like to avoid
>>>         processor choices that needs pricey tools. STM32 would be
>>>         nice. Of course some good ol' fashion assembly code, highly
>>>         optimized, would help things. Its been a while since I went
>>>         down that rabbit hole. I wonder if someone has an optimozed
>>>         FFT library for Cortex Mn??????
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--Tim Ressel
Circuit Abbey
timr at circuitabbey.com

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