http://www.soundonsound.com/sos/may02/articles/qa0502.asp
PC Music specialist Martin Walker replies: Full-duplex simply means that a soundcard can record and play back signals simultaneously. Nearly all modern soundcards are capable of doing this, although some elderly consumer models may have limitations on the sample rates or bit depths available. Similar restrictions may affect certain USB sound devices, since USB bandwidth isn't sufficient to run many 24-bit/96kHz audio channels simultaneously, for example.
I'm not surprised that there's still so much confusion about multi-client capability since, as you point out, soundcard specifications are often vague or nonexistent in this area. This is largely because it's not the soundcard that has the multi-client capability, but its driver software, so the capabilities of each soundcard model may change as new driver versions are released.
Being 'multi-client' can also mean various things: a soundcard may have multi-client drivers for its audio ports, its MIDI ports, or both, but each type is generally implemented in a very different way. For instance, if the soundcard's MIDI drivers are multi-client capable, you can send data to the same MIDI output from your MIDI+Audio sequencer and a synth editor simultaneously, which makes real-time tweaking of sounds far easier.
When it comes to audio, multi-client capability does allow you to run more than one audio application at once but, in this case, each application nearly always requires a dedicated stereo output. This may either be an additional physical output in the case of a multi-port card, or a virtual one in the case of models like the Echo Mia, where four stereo outputs are mixed internally and their combined signal sent to a single physical output. So yes, multi-client soundcards are certainly available and extremely practical, but each model may implement this feature in a different way.
The applications you use may also restrict the way you mix and match your audio I/O. For instance, if you use Cubase, it will always grab soundcard outputs 1/2, whatever driver type you choose. If other outputs exist, multi-client drivers will probably let you allocate these to other applications simultaneously, but only if you're using a different driver type. For instance,
with my Echo Mia card I can allocate ASIO channels 1/2 to Cubase, MME channels 3/4 to Wavelab, and GSIF channels 5/6 to GigaStudio.
Whenever I review a soundcard, I test out its multi-client capabilities with a variety of software, since this is often the only practical way to find out what its drivers are truly capable of, and I always report on my findings. However, new models are often launched with the promise of multi-client capability, even though this sometimes takes six months or more to appear.
I can't recommend a specific soundcard model, largely because I don't know how many inputs and outputs you need, whether or not you require digital I/O to connect up external gear and so on. However, I've written plenty of FAQs on this subject for the PC Music FAQs section of the SOS Forum at
www.soundonsound.com, and if you want to use a particular combination of audio applications, the easiest way to find out how practical this is with a particular soundcard is to post a query on the SOS Forum and see how other musicians have fared with a similar setup.
Topic: multi-client soundcards (Read 4776 times)