Richard Smith wrote:
On 4/4/06, carmen <[EMAIL PROTECTED]> wrote:


how expensive is a firewire port ?
firewire stuff is THE niche to fill.
most newer firewire devices are not supported if if i understand
correctly.


I'll ask.  That's a fairly large difference to the current design
though.  But if there was enough interest perhaps.
For it to fit into the current model someone would have to do the VHDL
code for a firewire interface rather than PCI.  I don't think Tim is
opposed to a totally different design but there would be less reuse
from what they already have.

If you want to build a firewire soundcard, use the 1394 chipsets already available from different manufacturers. Don't start writing your own VHDL... it's not worth it. They did the $2M investment to develop the ASIC and are selling their chips for a pretty good price.

From what I understand the BridgeCo DM1500, the successor of the DM1000 that is used in e.g. the edirol FA101 etc, has a price tag that is about the same of a FPGA that can implement the same functionallity.

It should also be able to do single packet latency processing with the DM1500 (1 firewire packet equals 8 frames). This would make the roundtrip latency of the DM1500 - D/A - A/D - DM1500 about 2*8/Fs + AD/DA latency. This comes down to about 1-2ms depending on the dataconverters used.

I've recently looked at the datasheet of the DICE-II chipset, and that also handles all firewire to audio (I2S) conversion and framing for >32 channels in each direction. But I don't know how it performs.

Count some extra latency introduced by the PC host controller though. I'm sorry to say, but a PCI based system will always be intrinsically lower latency than a FW based system. This is because there is a PCI-to-FireWire bridge present (the host controller). On top of that, virtually all host controllers are OHCI compliant, with only a few vendors selling OHCI chipsets (TI, VIA, NEC, ...) upon which all card manufacturers base their designs. Apparently only TI based OHCI chipsets perform good wrt lowest latency they can handle (although I can't prove this, someone that tested them told me).

Why reinvent the wheel? If anything firewire related should be built, the best thing would be a firewire host controller that has built in support for (de)framing the firewire packets, directly into host memory. But why bother using firewire device then...

And then we're not even talking about the drivers that have to be written... The freebob project at this point consists of only 2 people, notwithstanding the fact that we do have active manufacturer support and all nescessary documentation. The hardware is out, is priced pretty good and is of quite good quality (e.g. the edirol fa-101, $500 at zzsound.com). The basic functionallity is already present for a year (demo-ed at LAC last year), and we (at least I) expected that getting that code ready in time for LAC would help us getting more people interested in helping. But alas, up till now no contributions have been made.

So I ask myself: Would anyone here pay much more than $500 for a similar device that probably won't reach the same performance as currently available devices, and where the drivers still have to be written for. Based upon my experience, I might be sceptical, but I don't think so.

My opinion: If the community wants a GPL like firewire audio device, I suggest that you base it on the DM1500 chip, and help us out with FreeBob. That way you can actually get to a decent device with a decent performance in a realistic timeframe.


Pieter Palmers
FeeBob developer

PS: Although the previous might make you think the opposite, I'm NOT on the BridgeCo payroll nor do I own any BridgeCo shares.

PPS: The FreeBob project is written in such a way that other firewire based devices can be supported too. For the moment the DM1x00 based devices are the only ones we have the nescessary info for. But there might be others soon.

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