I think what we can all agree on is;
1) right tool for the right job
2) right level of knowledge to use the tool
:)
there is no one magic bullet for any solution.
Paula
On 2018-07-26 21:11, robert bristow-johnson wrote:
> ---------------------------- Original Message ----------------------------
> Subject: Re: [music-dsp] Creating new sound synthesis equipment
> From: "Sound of L.A. Music and Audio" <solastu...@gmx.de>
> Date: Thu, July 26, 2018 3:16 pm
> To: music-dsp@music.columbia.edu
> --------------------------------------------------------------------------
>
>> I agree that FPGAs do offer design techniques that cannot be done with
>> DPSs. But I hardly see them being made real in music instruments. The
>> reason might be that most people switch from C++ to the FPGA world and
>> try to copy their methods to VHDL only, so they do not make use of all
>> their abilities. Another point is inspiration what one can do :-)
>>
>> What I mostly see is the usage of pure calculation power and here, the
>> advantage of FPGAs decreases and decreases. When I started with FPGAs
>> there were many more reasons to use them then nowadays.
>
> from what i have seen, the need to design synthesis using FPGAs has to do
> with polyphony of, perhaps, 100s of voices. at least many dozens.
>
> this doesn't reveal anything that hadn't been public knowledge before, but
> the approach to synthesis hardware of Kurzwiel Music Systems has been with
> dedicated ASIC chips (that are expensive to spin), but they may since have
> migrated to FPGA. but the use of either, over the choice of a DSP (TI or
> SHArC) or an ARM, is simply the number of voices. if your application is,
> say, 20 voices or less, a single DSP can do virtually any previously-used
> synthesis method, even additive. with a 245 MHz SHArC, there are 2500
> instructions per sample at Fs=96 kHz. 20 voices would leave more than 100
> instructions per sample per voice. but this needs to be traded with
> bandwidth needed to do channel effects on the mixed voices.
>
> even though i have never myself developed anything for any FPGA (i come from
> the time of PALs), i still think the non-recurring engineering costs (NRE) is
> much higher for FPGA than with an off-the-shelf CPU or DSP.
>
>> When talking to musicans I often hear that MIDI processing and knob
>> scanning can be done with a little microprocessor because MIDI was slow.
>> In return there is no need for fast MIDI since people cannot press so
>> many knobs the same time, "we" cannot hear MIDI jitter, since musicians
>> do not totally stick to the measure either and so on.
>>
>> Facts are different and again in the "non music business" no subject of
>> discussion. In the industrial field, data transmission speed, bandwidth,
>> jitter and phase noise is calculated and the design is done correctly to
>> avoid issues.
>>
>> MIDI to me appeared to be a limiter for the evolution of synthesizers as
>> soon as I recognized it and understood the needs. I had a million of
>> talks about that too. You maybe know about my self designed high speed
>> MIDI. The strange thing about that is, that the serial transmission rate
>> of simple PC UARTs already exceeded 900kb 15 years ago, while MIDI still
>> was stuck at 31kHz.
>
> if we just let MIDI be what MIDI is primarily intended for, i still think the
> slow baud rate, opto-isolators, and the mostly simple protocol will still
> service live music applications well. MIDI has an event rate of but merging
> MIDI streams from several devices will always result in issues because we're
> pushing MIDI beyond its original intent. as it is, we can do about 1500
> events per second (assuming Running Status on the MIDI channel messages) or
> about 1000 events per second without Running Status. that's not a bad sample
> rate for knobs, foot pedals, a **single** keyboard player, even the output of
> control signals for envelope or LFO (having rates of 10 Hz or less). but
> controlling a dozen devices with a single MIDI stream gets to be problematic.
>
>> Am 26.07.2018 um 12:30 schrieb pa...@synth.net:
>>>
>>> I think where FPGAs score is in their ability to do lots of things at
>>> once, something not possible with a CPU or DSP. So going from Mono to
>>> poly is often quite simply a copy/paste (ok, I'm over simplifying it).
>>>
>>> I 100% agree about off loading stuff like USB and MIDI to a CPU, which
>>> is where the ZinQ and Cyclone SoC range really come into their own.
>
> actually, for a small device, like a stomp box that takes MIDI (say for a
> continuous pedal control), MIDI events can be decoded and dispatched in the
> "foreground" process. whatever MIDI 1.0 you receive, decoding the MIDI bytes
> takes maybe a half dozen evaluate and branch instructions in the MIDI parser
> state machine (i have C code that does this, i'm sure so do others), and
> executing the MIDI instruction should take just another dozen or so
> instructions. except for Program Change, that can take a lot more.
>
> but, if it's a full-on synth with dozens and dozens of layered voices, you
> will need a central CPU anyway because the sound-generating modules (be they
> FPGA or other chips) will be busy.
>
> --
>
> r b-j r...@audioimagination.com
>
> "Imagination is more important than knowledge."
>
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