[sdiy] Hardware convolution box?

Fri Feb 10 03:26:15 CET 2017

Check out my friend Dr. Paul Beckman’s site for tools https://www.dspconcepts.com/audio-weaver <https://www.dspconcepts.com/audio-weaver>

and my friend Tony Rouget site in Hong Kong https://www.minidsp.com <https://www.minidsp.com/>

and lastly my pal Al Clark’s site https://www.danvillesignal.com <https://www.danvillesignal.com/>  https://www.danvillesignal.com/landing-pages/snowbird-audio <https://www.danvillesignal.com/landing-pages/snowbird-audio>

These are good examples of audio products that are better than the DSP Manufacture can build.

and lastly my old friend from MIT Dr. Bill Gardner

https://www.audiobuildersworkshop.com <https://www.audiobuildersworkshop.com/>

hope this helps you guys a bit more.

regards,

Terry

> On Feb 9, 2017, at 5:20 PM, cheater00 cheater00 <cheater00 at gmail.com> wrote:
> 
> That makes sense, it's also a very solid way to do things, if one manages to dot all the i's so the result is an accurate copy of the naiive method.
> 
> 
> On Fri, 10 Feb 2017 02:01 Olivier Gillet, <ol.gillet at gmail.com <mailto:ol.gillet at gmail.com>> wrote:
> I think you're vastly overestimating how much computational resources
> this requires.
> 
> A well-known trick is to partition the head of the IR into small
> blocks (say 32 samples long if you want sub ms latency at 48kHz), and
> use larger blocks for the tail of the IR (latency is not a problem for
> the tail). The whole convolution can be decomposed as a sum of
> convolutions by each of the blocks, which can be evaluated in the
> frequency domain by DFT, complex multiplication by the DFT of the IR
> block, and IFT.
> 
> I did some back of the envelope computations and arrived at the result
> of 40 MMACs for a sample rate of 48kHz and a 2s-long IR.
> 
> I found it a bit too good to be true and I got back to the source:
> 
> http://www.cs.ust.hk/mjg_lib/bibs/DPSu/DPSu.Files/Ga95.PDF <http://www.cs.ust.hk/mjg_lib/bibs/DPSu/DPSu.Files/Ga95.PDF>
> p. 132, just before the beginning of section 6:
> 
> "Thus a filter of size 128K samples will require approximately 427
> multiples per output sample".
> 
> This assumes that the DFT of all the blocks the IR is made of has been
> pre-computed; but this can be done in faster than real-time when the
> IR is loaded, assuming you've got enough RAM.
> 
> Of course there's the issue of scheduling and a lot of additional
> bookkeeping, but at the very worst the order of magnitude we're in are
> hundreds of MMACs and a couple MBytes of RAM.
> 
> On Fri, Feb 10, 2017 at 1:09 AM, cheater00 cheater00
> <cheater00 at gmail.com <mailto:cheater00 at gmail.com>> wrote:
> > Found the right spot at the TI website. I've made a somewhat large
> > survey of AD and TI chips. I've uploaded the data to Google Docs (see
> > link at the end of this email).
> >
> > For a lot of power, TI can't be beat. Their chips are as cheap as
> > $0.78/GMACS, that's on TMS320C6678CYP, a chip with 8.5MB ram and 256
> > GMACS, $200 at Mouser.
> >
> > The cheapest TMS320C is TMS320C6652CZH6 with 19.2 GMACS, 1MB ram, at
> > $41.95 at Arrow.
> >
> > For cheap chips, AD is great. Their most powerful non-obsolete
> > offering is ADSP-BF561SKBCZ-5A, 2 GMACS, 328KB ram, $32.59 at Arrow,
> > for $16.30/GMACS. Some of their unusually cheap chips include:
> > ADSP-BF525BBCZ-5A, 1.2 GMACS, 132KB, $11.79 at Newark Element14 for $9.83/GMACS
> > ADSP-BF534BBCZ-4A, 1 GMACS, 134KB, $5.88 at Newark Element14 for $5.88/GMACS
> > ADSP-BF531SBBCZ400 0.8 GMACS, 53KB, $4.44 at Avnet for $5.54/GMACS
> >
> > Those chips were noticeably (3-4x) cheaper than their close
> > counterparts, apparently Newark and Avnet have some sort of blowout.
> >
> > I stopped surveying AD chips around 1.2 GMACS. There are going to be
> > much cheaper ones than I found, I guess, but they just have so many
> > chips I'd spend 2 days figuring out the prices. It's obvious: their
> > stuff is cheap.
> >
> > AD are inexpensive, but clearly, if you need a lot of processing power
> > and/or a lot of memory the TI will be 5 to 10 times cheaper. $200
> > might not be so much if that's the majority of the cost of the box for
> > a DIY gamer.
> >
> > As far as evaluation boards go, the highest-powered AD board seems to
> > be the best value. The TMDSEVM6678L costs $399 on TI's website, has
> > 64MB Flash, 512 MB DDR3 SDRAM, gigabit ethernet, usb mini-B, 80 IO
> > header and an AMC header with PCIe, an emulator port, a small FPGA for
> > configuration and booting, etc. See features at these two links:
> > http://www.ti.com/tool/tmdsevm6678#Technical%20Documents <http://www.ti.com/tool/tmdsevm6678#Technical%20Documents>
> > http://www2.advantech.com/Support/TI-EVM/6678le_of.aspx <http://www2.advantech.com/Support/TI-EVM/6678le_of.aspx>
> >
> > I don't know if the USB can be used in host mode. Does anyone know?
> >
> > It is unclear to me which version of the chip this board has - the
> > 320GMACS one at 1.25 GHz or the 256 GMACS one at 1 GHz.
> >
> > Finally, there is a version of this board that costs $599 (50% more)
> > and it has an XDS560V2 emulation mode. I understand that's a debugger.
> > I don't know why exactly it is significant. What advantages does this
> > bring for a developer?
> > Is the emulator port shown on advantech's website only available in
> > this more expensive version? If the cheaper version also has it, what
> > can it be used for if the XDS560V2 emulation mode is not available?
> >
> > Survey data is on Google Docs. Anyone can comment:
> >
> > https://docs.google.com/spreadsheets/d/1oT-9PVh8yZMMwAkpltqGo8mhSL1NLXZJiC-LH7swsbY/edit?usp=sharing <https://docs.google.com/spreadsheets/d/1oT-9PVh8yZMMwAkpltqGo8mhSL1NLXZJiC-LH7swsbY/edit?usp=sharing>
> >
> >
> > Have fun!
> >
> > On Thu, Feb 9, 2017 at 9:02 PM, cheater00 cheater00 <cheater00 at gmail.com <mailto:cheater00 at gmail.com>> wrote:
> >> Yeah, usb host mode sounds super useful unless SD will allow faster UI
> >> interaction.
> >>
> >> Do you know which TI chips have the most MMACS? I find the website
> >> confusing.
> >>
> >>
> >> On Thu, 9 Feb 2017 20:29 , <rsdio at audiobanshee.com <mailto:rsdio at audiobanshee.com>> wrote:
> >>>
> >>> Based on your survey, I'd recommend the Analog Devices board, even though
> >>> I usually lean towards TMS320. The TMS320 family is huge, including both
> >>> fixed-point and floating-point, low-power and high-speed, old and new
> >>> designs, etc. Some of the TMS320 boards you listed are really geared more
> >>> towards motor control than audio, which is why they might be underpowered
> >>> for long impulse response convolution. I know that the AD SHARC family is
> >>> also large, and they're very popular, but I am less familiar with the
> >>> options.
> >>>
> >>> Don't forget to look at the chip manufacturer as a direct source for these
> >>> boards. I always buy directly from Texas Instruments because Digi-Key tends
> >>> to have a markup. Outside the US, maybe it's a different story due to
> >>> international availability.
> >>>
> >>> I'd recommend something like the 1MB 800 MMAC board and not worry about
> >>> external RAM. 1MB seems like plenty. I'd also recommend trying to implement
> >>> both the time domain convolution and the frequency domain version. There are
> >>> ways to reduce the latency of the frequency domain approach, and at least it
> >>> would allow for longer impulse responses to be supported. For IRs that are
> >>> short enough, the time domain approach would work. I've also seen papers on
> >>> combining the two, since LTI techniques can be run in parallel and summed.
> >>>
> >>> As for taking pairs of 16-bit samples to speed things up, be aware that
> >>> not all instructions can work that way. I think that most DSPs can do a few
> >>> simple operations on value pairs, but the most complex DSP instructions can
> >>> only handle full samples. DSP architectures have internal registers that are
> >>> much larger than the sample size, like 56-bit or higher. If you think about
> >>> all of the potential overflow when adding thousands of samples from an
> >>> impulse response, you can see why such large registers are needed. When
> >>> working in that model, its not possible to handle the overflow from two
> >>> samples that are combined in a single 32-bit input value.
> >>>
> >>> Finally, I think that nobody has made something like this because the user
> >>> interface would be rather difficult. It's a bit of a power-user effect. On
> >>> that note, some sort of SD card might be useful, so I can see why you're
> >>> looking into that. However, perhaps just a custom USB class device would be
> >>> enough of an interface to allow downloading impulse responses to the device.
> >>> At a minimum, you'll need a large Flash to store the current impulse
> >>> response, or some way to partition the program Flash to set aside room for
> >>> the data. The AD board with USB host mode could feasibly read directly from
> >>> a USB memory stick or Flash drive.
> >>>
> >>> Brian
> >>>
> >>>
> >>> On Feb 6, 2017, at 9:20 PM, cheater00 cheater00 <cheater00 at gmail.com <mailto:cheater00 at gmail.com>>
> >>> wrote:
> >>> > Brian, $50 is a steal. I've had a look at Digikey.
> >>> >
> >>> > This TI board is £24. It has ~150 KB on-chip RAM, but it has an
> >>> > integrated SDRAM interface.
> >>> >
> >>> > http://www.digikey.co.uk/product-detail/en/texas-instruments/LAUNCHXL-F28377S/296-42484-ND/5404239 <http://www.digikey.co.uk/product-detail/en/texas-instruments/LAUNCHXL-F28377S/296-42484-ND/5404239>
> >>> >
> >>> >
> >>> > This TI board is £40. It has ~384 KB on-chip RAM and an integrated
> >>> > SRAM interface and SD card support. 200 MMACS.
> >>> >
> >>> > http://www.digikey.co.uk/product-detail/en/texas-instruments/TMDX5505EZDSP/296-24965-ND/2127652 <http://www.digikey.co.uk/product-detail/en/texas-instruments/TMDX5505EZDSP/296-24965-ND/2127652>
> >>> >
> >>> > This AD board is £60. It has 1MB on-chip RAM and USB host mode, no
> >>> > idea about ram interface or SD card. 800 MMACS.
> >>> >
> >>> > http://www.digikey.co.uk/product-detail/en/analog-devices-inc/ADZS-BF706-EZMINI/ADZS-BF706-EZMINI-ND/5408943 <http://www.digikey.co.uk/product-detail/en/analog-devices-inc/ADZS-BF706-EZMINI/ADZS-BF706-EZMINI-ND/5408943>
> >>> >
> >>> > This last one sports 800 MMACS. Is this enough processing power for
> >>> > the 5-second convolution I mentioned above? It seemed to me like that
> >>> > would need 4608 MMACs. Maybe 2304 if we take pairs of 16 bit samples
> >>> > and treat them as 32 bit values. Are my numbers correct? Are there
> >>> > optimizations that can be done to lower this number, while still
> >>> > having zero latency? I understand FFT domain convolution introduces
> >>> > latency, which is not wanted in hardware. "Naive" MAC based
> >>> > convolution doesn't seem too far out of reach.
> >>> >
> >>> > This TI board is £156. It has 256 KB on-chip RAM and support for DDR2
> >>> > SDRAM. No mention of MMACs but they say 3648 MIPS and I assume a
> >>> > pipelined MAC costs one instruction, would that be correct?
> >>> >
> >>> > http://www.digikey.co.uk/product-detail/en/texas-instruments/TMDSLCDK6748/TMDSLCDK6748-ND/5213032 <http://www.digikey.co.uk/product-detail/en/texas-instruments/TMDSLCDK6748/TMDSLCDK6748-ND/5213032>
> >>> >
> >>> >
> >>> > The more expensive boards don't seem to have more powerful DSP chips.
> >>> > And those chips don't really get much more powerful either. However,
> >>> > convolution is easily parallelised. So, worst case scenario, if you
> >>> > wanted really long impulse responses you'd have to use a few chips.
> >>> > However, even the really good 800 MMACS Blackfin ones are £15 unit
> >>> > price, so that's not so bad...
> >>> >
> >>> > So, tell me, why hasn't anyone made this yet?
> >>> >
> >
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