[LAU] jack2 set to realtime / soft mode, normal kernel ?

[david]

Arnold Krille wrote:
> Hi,
> 
> On Saturday 10 July 2010 23:16:40 Harry Van Haaren wrote:
>> Advantages of firewire approach:
>> 1. Bus design. Internally, the firewire chip doesnt have to ask the CPU to
>> copy data
>> to its port, it just does it, while USB devices use the CPU for this task.
>> 2. On cheap laptops (and unfortunat others) the IRQ's between USB &
>> something else
>> collide. This means worse performance. (I'm aware that Firewire IRQ's can
>> collide too,
>> but I've never seen that phenomena before.)
>> 3. Firewire daisy chaining does still exist, at least for the Echo
>> Audiofire devices that I have.
>> 4. I run a laptop (so PCI / PCI-E and a lot of other options are out. )
>> 5. From my experiences, Firewire devices seem to be more geared towards
>> professional use,
>> while USB targets the "pro-sumer" market. (No flame bait intended here..)
> 
> Here are more firewire-advantages:
> 
> 6. Synchronous transport for streaming data. Also streaming stuff is initiated 
> by the device, not by the cpu.
> 6.5 This results in a bus-wide clock to sync devices which enables the daisy-
> chain usage of multiple devices.
> 7. Guaranteed bandwidth and latency (up to a certain maximum), devices will 
> not steal each others time as with usb.

On either of my laptops, if I plug my UCA-202 USB1 card into its own 
USB2 port, I get smooth audio performance (24-bit/48kHz).

If I try to daisy chain it through my external USB2 hub, I get choppy 
audio (and a noticeable hum, that could simply be the hub's ungrounded 
external power supply or poor shielding).

My church uses an Echo AudioFire 12 to record our services. We used to 
record 12-tracks 24-bit/48kHz to an old IBM Thinkpad via a Firewire 
card. It recorded skip free on old equipment that could only do Firewire 
400 speeds.

So even though NOMINALLY the USB port is FASTER - Firewire gives better 
sustained throughput. That's why Firewire is still the preferred method 
for connecting pro digital video - sustained throughput.

As long as any device on the USB bus (like a mouse or computer keyboard) 
can interrupt another device's data transfer, I don't think USB is ready 
for serious audio work even if your PC hardware supports enough USB host 
controllers to give your audio device its own USB port.

-- 
David
gnome at hawaii.rr.com
authenticity, honesty, community