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Old 11th December 2007, 03:38 PM   #11
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Default Taking this thread back to a non-PC solution...

Daveis: I see the ADSP-21261 is part of the Sharc family of processors which I think are used in the DCX2496. Is this why you went in that direction? Did you get anywhere? If you no longer want/have use for the development kit I'd be interested in buying it.

OzOne: The Blackfin is a superb processor. I read about one commercial Audio Processor that uses two Blackfins to get the job done. Obviously things get extremely expensive at that point. I think in order for this project to work (regarding price and development time) it will have to rely heavily on open source code and the experience of people who have already been down this road. After doing some online research I think much of the information and code is available, though some may be for a different platform. I'm still 100% interested in this project and I'll call on anyone else who has DSP experience to chime in. Even if only to give me a pat on the head

Everyone: Please post any links you know of to code or information on audio DSP. In particular for the Sharc family of processors since this is the direction I'm leaning at the moment. Before someone points it out, I'm aware a DSP developement kit alone will cost more than a Behringer DCX2496. I'm willing to absorb that to get a solution for everyone.

Time to get the ball rolling on a non-PC solution.
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Old 11th December 2007, 04:30 PM   #12
anbello is offline anbello  Italy
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Sorry slightly OT, my current PC based system to do DRC:
- old PC with 500MHz PIII with 512MB RAM, + HD + ...
- Terratec Aureon 7.1 Space (Envy24HT - spdif in and out - spdif in can be used for external synch)
- linux kernel 2.6.(don't remember - i' am at work now) recompiled for low latency
- jack
- brutefir
- DRC to calculate coefficients filter for brutefir after measuring my audio set + room.
The interesting thing about this system is that with such an old PC brutefir apply the filter with 32768 taps in realtime using only 20% of the CPU.

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Old 11th December 2007, 05:14 PM   #13
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I can certainly understand the desire for a non-PC approach to DSP, but it's never really caught on in these forums. I think there are a bunch of contributing reasons

- specialized skill set - not many high-level DSP programmers hang out here
- specialized hardware; moving beyond the use of EVM/DevKit packages is highly non-trivial
- timelines - hobby stuff moves relatively slowly, and staying current with the hardware tech can be a challenge
- horsepower. If all you want is IIR filters, modding a DCX2496 is way easier than building from scratch. OTOH, a single DSP chip will be very hard-pressed to handle high-rate multi-channel FIR filters without some serious programming (see point 1)
- you still need all the other stuff like good DACs, volume control etc

I started off years ago on Motorols DSP56k dev kits, and quite happily bailed out the day I discovered BruteFIR. IMHO the downsides of the PC approach are outweighed by the convenience and flexibility.

I do think that peufeu's ethernet/fpga/I2S project holds the promise of the best of both worlds - PC flexibility on the software side with somewhat more conventional hardware that "should" be easier to optimize than a PC approach. It seems to have stalled for the moment, though.
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Old 11th December 2007, 06:07 PM   #14
Daveis is offline Daveis  United States
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Default Re: Taking this thread back to a non-PC solution...

Originally posted by Kevin_Murray
Daveis: I see the ADSP-21261 is part of the Sharc family of processors which I think are used in the DCX2496. Is this why you went in that direction? Did you get anywhere? If you no longer want/have use for the development kit I'd be interested in buying it.

I followed a forum link about someone wanting to do audio processing with DSP. Yes, I recognized the chips as being similar to DCX2496 (which I previously used). I discussed with engineers at Dansville to see if it was in the ballpark of the processing power I needed. I think at the time I just wanted a 2-way stereo crossover.
I'll go look for the manual and board. It may take a while to find it all.

About the same time, I became aware of Voxengo Pristine Space convolver, brutefir, and Thuneau's IIR.

I went down the road of Windows PC, good sound card (RME), good external DAC's.

The cost in amps and DAC's has been significant. And I am stuck with only a stereo system that doesn't interface with my HD DVD player. (at least not without an A/D conversion) And I misuse a 6.1 multi-channel receiver as volume control. And I have cables running out to the living room littering things.

DRC by itself, however, seems a much more compelling use of DSP's.
You are talking just an FIR convolver for maybe one or two channels at a time.

I think it's when you add crossover functions into the mix that DSP becomes unwieldy due to the number of channels involved.
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Old 11th December 2007, 06:34 PM   #15
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Hi all,

@sunra - I looked into peufeu's project some time ago - it looks great, but I think the main aim of it was to separate the PC side more from the audio / DAC side to isolate noise, buffer the data etc.

@all - Although I'm still very much interested in at least working out if this project would be feasible, I can see how the costs could quickly add up etc. This has got me thinking about the PC approach again because the improvement I've had from using DRC is huge.

Atm, I don't have the PC hooked up for 7.1 due to moving rooms and upgrading the PC. The issue is that there's no easy was to use the AV amp as normal, then apply DRC to all channels (ie. I can't use the DD / DTS / PLII / THX processing on the amp, then apply DRC to the speakers.)

Then again, DRC addresses one of the main features that THX processing addresses - re-equalization. Because of this, enabling THX while using a standard house curve via DRC would probably take too much treble off.

Really, it all comes down to the practicalities of using a PC for constant listening. Also because I hate having analog connections to the amp and it would be fantastic to use I2S links directly (especially after reading Brian Brown's thread about the muxit interface.).....

High Resolution Multi-Channel Digital Interface

@anbello - how does your system handle external 5.1 / 7.1 inputs? Or do you use the PC as the DVD player? Or, are you mainly using it for 2 channel audio?

@dwk123 - if you're interested in having an I2S link to more conventional DACs, I would highly recommend modding a sound card with a muxit interface (for 2 channel and full 5.1 / 7.1). I haven't got round to testing this myself yet, but fully intend to soon. (edit: forgot you are already using equibit amps etc. I'm guessing you're way past the I2S point - ignore this part! )

@solve - I can't use asio4all because of the way I loop Windows audio through VSTHost using the Audiotrak drivers. eg....

Winamp > drivers (WDM to ASIO IN) > VSTHost > ASIO out to speakers.

...If I used asio4all, it would try to play the audio through WDM again, which is effectively already in use for the "incoming" audio from Winamp / Windows apps.

What I'm trying to get away from is having these glitch problems with the audio and chaging more towards a great project we can bolt bits onto and start programming / learning with. This would also allow people to add better DACs (if going the analog route) and add features.

(I'm pretty good with PIC chips / FPGAs, but useless with C++ / Windoze / Linux programming, so I'd personally love to mess around with DSP chips / LCD screens / I2S etc.)

We basically need a DSP guru to tell us if this project is achievable without costing more than a Beatles court case!


Edit: Almost forgot - here's another example of how expensive these things can be.....

Interestingly, to use this for DRC, you have to measure the room's response first, send the data off to the manufacturer, then have them send the correction info back - I can already do all this myself with open-source software! Again, another advantage of having our own unit.

Surely there must be many manufacturers missing out on a big market share? I'm sure plenty of people would be interested in a resonably priced DRC solution to add to their home theater / hifi setups?
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Old 11th December 2007, 07:23 PM   #16
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This is what I suspected. Fortunately this project relates to my job so in time it will happen (plus I'm stubborn). Regarding keeping current, I'm finding out just how much has changed since I've been away from DSP. There is some impressive hardware available now, though it's making choosing a platform more difficult

I expect I will be doing nothing but reading through the new year. I hadn't planned on determining a hardware configuration till the end of January. Initially I had planned on just a crossover and maybe delay added in. I think that parameteric eq wouldn't be too hard to integrate with DRC the ultimate goal. I see that some people are interested in 6-8 channel DSP which is a processing nightmare, unless going to multiple hardware paths. Maybe a feature wishlist would help to generate a block diagram which would then help determine hardware requirements?

Food for thought:
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Old 11th December 2007, 08:46 PM   #17
flshzug is offline flshzug  Antarctica
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Hello, I think you guys missed the bandwagon, there were Xilinx Virtex4 ml402 devkits on ebay for months, for laughable 200-250 usd with lvds io. Afaik the debugger for the ADSP sharc is not free like the xilinx webpack , only for x days with the Ev-kit, then restricted mode.

I have a Lynx AES -16 ( similar to RME aes-32 ) and i want to use it as digital crossover too. Basically all i want to see in relation to the pc case is xlr cables. Ive yet to plug the soundcard in, but I know it shows up as 8 2in 2 out audio drivers. The winamp -> VST route is what i want to do, and just reroute the filtered audio to a pair of XLR's. BTW, any monoblock ideas to power hi-eff (95.4 dB) JBL 15 inchers?
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Old 11th December 2007, 10:08 PM   #18
flshzug is offline flshzug  Antarctica
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forget to mention , on the ADSP sharc , you can do 96khz convolution reverb in stereo for 10 or 20 mhz I dont recall, so its quite nice as it is ^^
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Old 12th December 2007, 03:13 AM   #19
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Yes it's now free for 90 days and probably reduced function at that. I'm waiting till I'm ready to start coding to register. I also hope to convince my boss that this will be a useful addition to the company knowledgebase. ;-)

Thanks for the ebay teaser too. A**hole. ;-)

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Old 12th December 2007, 06:30 AM   #20
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I've just ordered up a Analog Devices 21262 EZ dev board. I'm a hardware & C/C++ guy looking to add DSP chops to my resume. I am looking for a good audio project to learn on. Maybe this is it. I've never worked with the AD DSP software tools. Are they any good? How about open source and freeware tools and libraries? What's out there?

Best Regards,
Carl Huff
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