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ASIO vs. WDSM drivers?

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ASIO vs. WDSM drivers?

Postby roochero » Wed Oct 26, 2005 7:34 pm

I am informed that ASIO performs better in the latency stakes. How much of a difference are we talking?

The benifit I aim to get from WDSM is that i can run 2 soundcards simultaneously. Worth the switch or wasting my time?
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Re: ASIO vs. WDSM drivers?

Postby Jim Y » Wed Oct 26, 2005 7:52 pm

WDSM?

If you're running a Cakewalk program, there should be little advantage to switching to ASIO, but it depends on the drivers. Some are WDM drivers with an ASIO "port", some are more specialised with ASIO in mind and the WDM support is actually an add-on that often has limitations.

So it depends on the program you use and the makes of the soundcards.
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Re: ASIO vs. WDSM drivers?

Postby roochero » Wed Oct 26, 2005 7:56 pm

Program would be Tracktion 2.
Soundcards are Mackie XD-2 and DMX 6fire.
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Re: ASIO vs. WDSM drivers?

Postby Wurlitzer » Wed Oct 26, 2005 8:11 pm

I don't believe ASIO actually is better than WDM, is it? It was certainly better than the old (MME) native Windows drivers, and for that reason many people still presume it is the best. But WMD drivers are a whole new bag.

Both ASIO and WDM should be capable of unnoticeable latency on decent hardware. I'd use whatever suits your software best, and put practical considerations (such as wanting to run two soundcards) first.
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Re: ASIO vs. WDSM drivers?

Postby Jim Y » Wed Oct 26, 2005 8:36 pm

Ah, no, this is not that simple.

This is where the industry is confusing itself and everyone else by not using the proper terms.

WDM is a type of driver architecture. Audio programs don't need or want to know about that.

The programs use one or a choice of audio API's (Application programming interfaces). It's the interfaces provided by the driver that differ. There is no such API as WDM!!!!

I'm going to have to start slapping people who say "WDM driver" when they're refering to one of the following possible WDM driver "interfaces"!

ASIO = Low latency API (optional)
GSIF = Low latency API (optional)
The next three are always available in any WDM driver
MME (aka WAVE) = High latency API
DirectSound (DS) = High latency API
WDM/KS = low latency API

The last one is the clincher. The important term here is the KS = Kernal Streaming. It is an API all WDM drivers have. When speaking of it the term KS must always be used. "WDM" on its own is meaningless, because it can just as easily refer to MME or DS.

So what does Traction mean by WDM? It could be MME, DS or KS. Only KS will give you low latency and few programs actually support it. I think ASIO would turn out to be the best option, but then you can only have one soundcard driver.
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Re: ASIO vs. WDSM drivers?

Postby Stevedog » Wed Oct 26, 2005 8:39 pm

I use the ASIO Echo WDM driver with my card Echo Darla 24
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Re: ASIO vs. WDSM drivers?

Postby Sle » Wed Oct 26, 2005 10:59 pm

WDM: "Windows Driver Model".

Does anyone remember the hoo ha about changing to XP and having to have these for everything?

Back to the topic, there are a number of ASIO cards that support cascading, and most systems will get along with more than one device, if not allowing simultaneous use. My VST ASIO driver is WDM, yet has nowt to do with DirectX.
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Re: ASIO vs. WDSM drivers?

Postby Jim Y » Thu Oct 27, 2005 3:56 am

"ASIO WDM" probably refers to it being a WDM driver with an ASIO interface - as per my list above. Hopefully this knocks on the head the idea that these are neccesarily seperate entities.

However, the original question begs another one, "What does Tractions designer/s mean by WDM"? I don't know, I don't have it.

Cakewalk started all this by first supporting WDM/KS in Sonar 1.0 but called it plain WDM. They're precise about it now. Is it so hard to say "WDM/KS" or just plain "KS"?

As a matter of fact, asio4all adds ASIO to a WDM driver by acting as a translator between a host program using ASIO (eg, Cubase) and the drivers KS interface.

Designers arn't restricted to WDM drivers. Digidesign have their own driver design, to which other interfaces are "sometimes" available if you're lucky. I believe MME is only available for stereo playback?.
The E-mu ASIO driver requires you to connect a stereo MME (wave) driver to your choice of channels if you want to use that API.
RME have an MME option that's just as fast as their ASIO (allegedly). Not everybody uses WDM for the driver design.

Cubase can translate interfaces itself, providing an adapter layer for ASIO multimedia (the MME interface) and ASIO directsound (in playback only or full-duplex flavours). Neither of these two are ASIO, it's just that Cubase always uses it's ASIO protocol to communicate with the audio interface driver.

The basic latency of DirectSound and MME with a WDM driver is about 30ms. So that's one way to tell if your program is using either KS or one of those two.

Another tell-tale is that when a WDM driver is being accessed via KS, MME and Directsound can't work. WMP for example can't playback, neither can the Microsoft GS software synth be used for midi playback as it needs the DirectX api (directsound and directmusic).
Converse, while MME or Directsound are using a WDM driver, a program set to use KS can't open the driver - it's in use. Sonar users must have seen that a few times!

Yet another. If your audio interface driver control panel has the option to be locked to a particular sample-rate, then all audio files/projects with different rates to that and played using MME or Directsound will still be heard at the correct speed. Sample rate conversion is provided with these API whenever the hardware interface cannot itself adjust its clock to the required rate. WDM/KS and ASIO however, will play at the incorrect rate.
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Re: ASIO vs. WDSM drivers?

Postby Sle » Thu Oct 27, 2005 10:45 am

I may well be wrong here, but I was under the impression that all drivers on an 0S2/NT (For instance XP) system had to conform to WDM, be they graphics, sound, whatever. I believe you can make any type of sound driver from your list WDM compliant, they had to to make them XP compatible.
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Re: ASIO vs. WDSM drivers?

Postby Jim Y » Thu Oct 27, 2005 2:34 pm

Windows drivers don't have to be WDM. The original NT kernal model is still available to build a bespoke driver on. However, if they aren't WDM, some of the features of Directsound or MME may not be available or severly restricted. That's of little concern if the primary use of the audio interface is ASIO or Protools under one main DAW application.

Apart from allowing KS, WDM provides DirectX and MME with...
Multiclient support - several sources can use the driver.
Multiformat support - different bit depths and sample rates are automatically converted and mixed to match a common driver format.
Complete format support - automatic conversion from a format not supported by the hardware (eg, many AC97 chips only support 16bit/48Khz in their hardware).
Midi playback with the GS soft synth. (There are other Midi facilities available, such as time stamping of messages - Midi is included as an audio resource in the WDM system using MME or DirectMusic API.)

Multiple hardware interfaces can be used together or seperately.

All the above obviously uses CPU resources, however it's quite clever in that if the audio chip has the facility to handle these tasks in it's own hardware (samplerate conversion and mixing), the WDM system passes the seperate streams directly to the chip to do the work. AKA "Hardware Acceleration".

In a DAW, most users wouldn't want anything that might cause anything less than perfect bit-for-bit flows of audio to and from the hardware interface converters. Only API such as ASIO or WDM/KS (and whatever Digidesign use) can ensure this is so, together with an interface that doesn't employ sample-rate conversion in it's hardware. MME and DirectSound can be clean, but only if the currently available resources allow them to be (no other sounds playing and the rate required is supported by the hardware).
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Re: ASIO vs. WDSM drivers?

Postby Martin Walker » Thu Oct 27, 2005 3:40 pm

And sometimes it's been known for a low-res system sound to cause sample-rate conversion to kick in with the MME and DirectSound drivers, but then stay active behind the scenes afterwards, even when playing back sample rates that are already directly supported by the hardware - this is one reason why many people recommend that system sounds are disabled in a music PC.


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Re: ASIO vs. WDSM drivers?

Postby Jim Y » Thu Oct 27, 2005 8:03 pm

I've been experimenting with an Audiophile2496 as the sole interface in an XP pc, whatever I set it's clock rate to (but not locked), following a reboot it's always on 22khz. It would appear Windows sounds has initialised for playing even if it doesn't make a sound.
However, whatever sample-rate the audio is that I play next will switch the cards rate to the correct one, including DirectSound playback of an audio CD with Windows Media Player.

When another interface is available, such as having the onboard AC97 enabled and selected for Windows sounds, the AP2496 rate remains whatever was last set before last shutdown. This may be the best way to deal with it - give Windows sounds something harmless to play with!

Bearing all this in mind, owners of interfaces that can display the current hardware clock rate would do well to have a look at it from time to time, especially if you're relying on clean audio with a mediaplayer or an MME program like CoolEdit or Audition. Just for fun, lock the drivers rate on 8Khz and play a CD in WMP. Right pitch, crap sound!

Here's a case when Windows SRC doesn't kick in. If I have the soundcard set to slave to an external clock, and that clock source has vari-pitch (A Roland VS recorder varies pitch via sample-rate for instance), MME and DirectSound played over this interface follows the vari-pitch. WDM doesn't know the hardware sample-rate isn't correct so doesn't convert the source audio.
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Re: ASIO vs. WDSM drivers?

Postby roochero » Thu Oct 27, 2005 8:22 pm

Ta for the advice. Very much appreciated.
Being green around the gills I reckon i'll simply splash out on Tracktion 2 and stick with the single DMX 6fire soundcard. The extra inputs would have been nice, a pity as the xd-2 is bundled with T2 for only £40 more.
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Re: ASIO vs. WDSM drivers?

Postby Wigworld » Thu Oct 27, 2005 8:27 pm

The main issue I have with ASIO drivers against WDM drivers (OK, Jim, WDM/KS drivers ;)), is that ASIO drivers will only let you use one audio interface at a time. With WDM/KS, you can use multiple interfaces.
Often the differences between the two API/driver types is that functionality is different between the two e.g. the ASIO driver for the Emu range of soundcards has more functionality than the WDM/KS driver, which only allows recording from one pair of inputs at a time (ASIO allows simultaneous recording from multiple inputs).

How I miss the days when all you had to worry about was whether or not a card was full duplex!
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Re: ASIO vs. WDSM drivers?

Postby roochero » Sat Oct 29, 2005 4:38 pm

Just had response from Mackie. The driver options are ASIO or WDM/DS (direct sound). Based on the latency issues I may experience through DS I've gone and ordered Tracktion 2 on its own and will continue with the DMX 6fire. Once again, thanks for the response; saved me a few quid.
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