14 Jan
2005
14 Jan
'05
3:07 p.m.
On Thu, 13 Jan 2005 19:57:41 -0500, Jon B wrote
Yup. Your latency is "frames per period" / sampling rate.
Recommendations so far:
1. Echo Indigo I/O
Looks good. Only thing I'm worried about is the converters being
inside the computer. Is it really well-shielded and flat noise
floor? I guess if there's some whine but it's *much* lower than a typical
sound card, I could live with that. They look pretty inexpensive,
regardless. $180 or so. Maybe I should just get one and try it.
The converters in the Indigo sit just outside the computer. The card plugs in
and the converters/amplifiers/jacks stick out about an inch from the CardBus
slot.
Here's a picture:
http://www.stereophile.com/images/archivesart/1104indigo.1.jpg
The sound quality I have found to be very quiet, even at high gain- definitely
a cut above any internal PCI sound cards I have heard.
Here's an article that talks about Indigo's sound quality:
http://www.extremetech.com/article2/0,1558,1325716,00.asp
They deliver
real-time performance at 96kHz, 24 bit
down to 32 samples.
By "down to 32 samples" are you talking buffer size? Is this what
JACK calls "frames/period"? So PCMCIA is definitely capable of low latency,
comparable to an
internal sound card? (Comparable to PCI, I guess?)
It seems to be less an issue of the bus (PCI vs PCMCIA) and more an issue of
how the hardware is configured-- IRQ assignments, DMA on disks, kernel
tweaking, etc. For me, portable low latency was the deciding factor for going
with the Indigo IO and it has paid off.
I am looking for something in between these in price
range. $300 or
so. The Indigo would probably be ok, but maybe better than that...
Is there anything with MIDI, too? I haven't learned enough about
MIDI interfaces to understand the kind of latency involved, or used
it very much with ALSA, but something that could handle both at low latencies
would be great. (Or two separate things, but I only have one PCMCIA
slot.) I have a Midisport 1x1, but it has bad latency in windows,
and I haven't bothered to figure out how to get it working in Linux.
Your latencies in MIDI are going to come mostly from the transmission protocol
itself. It uses a slow data rate, so it'll always have millisecond latency.
Good Luck,
-JP Mercury