Hackers wanted for Ethernet DAC team project.

[peufeu]

What I want to do

Build the ultimate PC audio solution : a no-compromise DAC which handles multichannel audio up to 24-192, custom upsampling filters, volume control, brutefir active XO in the PC, easy to use, appears like a soundcard to a Linux JACK system, press Play on the media player and it just works.

How

* FPGA module connected to PC through 100Base-T Ethernet :
- provides packetized audio streaming ability.
- FPGA contains a Microblaze CPU and peripherals.
- 4-8 megabytes of SDRAM on board.
- FPGA can do signal processing including 4-8x oversampling from 44.1k.

* DAC module
- onboard low-jitter master clocks for 44.1k and 48k based sample rates
- no ASRC
- FPGA module and PC are slaved to this master clock
- DAC, I/V
- and volume control (probably LDR) controlled by PC

* PC software
- Linux JACK driver to appear as a soundcard
- standard JACK-aware media player application, user choice

Current status

- Working prototype with Suzaku FPGA module connected to my old DAC
- no JACK driver
- oversampling with sox
- it works and sounds good
- URL : http://audio.peufeu.com

In development

Version 2 with a new, improved FPGA module should be done and working by October 15. FPGA module has LAN9117 with magnetics, Spartan 3E-500 and 32-bit fast SDRAM. All available FPGA IOs will be routed to a Hirose connector.

What you can do

I will build the FPGA modules, do the embedded coding and HDL, to get a fully functioning ethernet audio streaming system. I will publish the UDP protocol specs and pinouts.

I would like to create a team to work on this project. Things that have to be done are :

- write a driver for JACK (needs C/C++ and linux programming skills)
- write a driver for Windows
- build DACs and experiment
- software to display the songs titles on a LCD
- replay gain handling with onboard volume control
- remote control
- etc.

If you are interested, please post.

Project timeline

Phase 1 (up to end of October 2007) :

I build a FPGA module prototype and make it work.

Phase 2 :

Gather a team of motivated people. FPGA module group buy. I will handle the manufacturing, since this is likely to involve some pretty funky SMD soldering. So, I will build the stuff and sell the modules at parts cost (about $100).

I would like to gather maybe 3-5 people, everyone having the same module and hacking. You probably all have some DAC boards somewhere to connect to it

Phase 3 :

Design of a DAC mainboard and plugin modules for various DACs, I/Vs, volume controls, etc. The idea is to get an experimental platform to try many DAC chips, IV design candidates. Once common connector pinouts are decided, anyone can build plug-ins, listen, mail them to buddies for other listening tests, etc. This should be pretty interesting !

Phase 4 :

Decide the best plug-ins, make a one-board DAC, and go !




Who's in ?

[dwk123]

I'm in, and have indicated to peufeu that I'll start looking into the Jack driver.

I think this stands to be the coolest project I've run across in a long time.

[ezkcdude]

Peufeu, you need to track down the 8-year-old kid from this article:

http://www.eetimes.com/news/latest/s...printable=true

[TriLithium]

This project sounds great, I always was very excited with your V1 board with the Suzuka.
If there is any way you could use a down-to-earth hardware guy then I would be participating also.
Lot of experimenting to be done as it seems, Great!

[ejaouen]

I would love to be in to.
but I fear I will not be much useful to you as I have not anywhere near your knowledge.
Do you accept me peufeu ?

In fact I would like to buy a soldered FPGA module from you (at about cost price would be great).
That way I could try it on my computer and tell you if the module is working !!

Also count me in for the future DAC and plugin boards test and chip I/V comparisons.

This project is exactly what I need and what I was dreaming of !

Eric, France

[soundcheck]

Hi peufeu.

I tried Jack. It really made my sound worse compared to my tweaked ALSA USB audio
driver.
So better be careful not to waste too much time on Jack drivers if you really want to go for the ultimate PC solution.

Using a standard player is IMO also the questionable path here if you're after best sound.
The no-frill apporach is to my experience a must for best sound. Why don't you just use brutefir as a player as I am doing it.

I am still wondering if the whole FGPA thing is worth the effort. The other day Takashi Iwai form ALSA was mentioning something about an externally
clocked USB bus. That would be really cool, if that ever comes to life!

However. Good luck with your project.

Cheers
Klaus

[peufeu]

Thanks for your interest

There is no point in building several copies of the device before the first FPGA board is working, thoroughly tested, including full ethernet bandwidth etc. I'd hate to screw up and have a few non-working PCBs, considering the price of 4 layer prototypes.

So, the only help I would need right now is proof-reading the FPGA design and PCB to check if I screwed up. Or, if you own a PCB fab, or digikey I have to rethink the layout a bit, again...

When the first one works, now, we can talk, and hack

soundcheck :

- did you make the "bit exact test" ? (ie play something, record it, check for differences, by looping back SPDIF output to input). For instance some sample rate conversion, or truncation, may slip in in unexpected places, and you can detect that.

[soundcheck]

Originally posted by peufeu
Thanks for your interest

soundcheck :

- did you make the "bit exact test" ? (ie play something, record it, check for differences, by looping back SPDIF output to input). For instance some sample rate conversion, or truncation, may slip in in unexpected places, and you can detect that.

Bit-Perfection: Always a nice issue to discuss!

My PCM2707 wouldn't even support looping the stream.
However. I do not have dmix in the loop. Nothing will be resampled.

I also read quite some people done the "Bit-Perfect-Looping-Test" on setups you
wouldn't expect bit-perfection if you listen to them.
Assuming a bit-perfect stream, what I do - and I really dont know how to test this in my setup, it IMO won't tell you anything on the induced non-lineartieries and/or jitter, thus sound quality.


Cheers

[peufeu]

Sure, it doesn't guarantee good sound, but bit-perfect test avoids some turd-polishing

Like, especially on windows when some unexpected processing is added without the user's knowledge. Or CD players that mess with the data.

You removed all the fluff from your system, so you should be safe

It's mandatory anyway for DIY (I looped back my I2S output to I2S input to test), cause it's easy to slip a bit or get the shift registers wrong and end up with 15-bit audio.

[dwk123]

Originally posted by soundcheck
Hi peufeu.


I am still wondering if the whole FGPA thing is worth the effort.

When you get 8 channels of 24/96 playback from your approach with NO sensitivity to activity on the PC, then go ahead and wonder. Considering the degree of effort you seem to have spent on getting 2 channel 16/44.1 working and yet STILL have a very high degree of sensitivity to system activity, I fail to see why you would 'wonder' about this approach.

I'm with peufeu on this - if the playback quality on your system is sensitive to software activity on the system, that is a flaw. It is NOT a sign of transparency or quality.

I tried Jack. It really made my sound worse compared to my tweaked ALSA USB audio
driver.
So better be careful not to waste too much time on Jack drivers if you really want to go for the ultimate PC solution.

If the only way to get decent audio out of a PC is to throw away all the cool software that makes a PC better than a CD player in the first place, why bother? Really, what you seem to have done is moved away from a CD player to a PC, and then spent a whole lot of time and effort trying to turn the PC back into a CD player again, simply because your clock is overly sensitive to external influence.

The answer seems simple - use a clock architecture that is immune to influence from the PC. Once that is done, then you can use the PC with all the cool software available without having to worry one bit about audio quality. This is the primary point of peufeu's design.