Subject: Re: [linux-audio-dev] USB Souncards
From: Kai Vehmanen (kai.vehmanen_AT_wakkanet.fi)
Date: Sun Jan 20 2002 - 15:25:25 EET
On 20 Jan 2002, Allan Klinbail wrote:
> I'd try and steer away from USB audio...
> Reports in magazines like Sound on Sound and Audio Technology (an
> Australian publication) don't rate any USB audio devices highly .. due
> to the low bandwidth and shared nature of the USB protocol. i.e. the
> FOstex USB Midi/audio desk (sorry can't remember the model) can't handle
> full spec MIDI and all audio processes at one time...
On the other hand USB does offer 12Mbit/s of bandwidth. In real life you
don't get the theoretical speeds, but around 5-6Mbit/s of reliable
throughput is possible even with other low-bandwidth devices connected on
the same bus. This means you can transfer 7-8 cd-quality channels. So at
least something like 4 audio channels + MIDI seems reasonable. A different
issue is whether any of the current USB audio devices can achieve this.
The biggest problem I have with USB is the USB specification itself.
Compared to simple old standards like MIDI, USB is big and complex.
There's lots of details and lots of room for interpretation, both on the
host and device side. It has taken years for the host-side implementations
to become stable. And still nowadays, whenever I plug or unplug an
USB-device, I'm waiting for something bad to happen (system halt, host
driver segfaults, handshake failures, etc, etc). These qualities are
something I don't want my audio interface to have...
But to not sound too negative, when it works, it works well. ;)
> When using laptops it is highly recommended to use a firewire hard disk
> as your recording media as the latency of the hard drive on even the
> best laptops is unacceptable under any OS (especially when multitracking
> even just on output).
I disagree with this. A properly written audio application can take care
of this. As a matter of fact, all apps should take care of this, as even
on desktop systems, harddrive latencies are often unacceptable for any
realtime use (not necessarily because of hw, but because of operating
system buffering).
-- http://www.eca.cx Audio software for Linux!
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