[sdiy] IR Reverb

Martin Klang mars at pingdynasty.com
Tue Feb 20 14:19:56 CET 2018

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...


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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