Which Interface: MME, Windows DirectSound or WASAPI?

Audacity 2.0.6, .exe, Windows 7 Pro
I noticed the three interfaces. I read the FAQ and found MME gives widest compatibility. If my USB (Behringer) works OK with all three interfaces, which one is “best”? The latest? Or does it matter? Application is just recording from cassette tape. Thanks.

Or does it matter? Application is just recording from cassette tape.

I don’t think it matters unless you get a glitch and for some reason one protocol one works better than the other. I’d be very surprised if there is any difference in audio quality. WASAPI is the “latest & greatest”.

In general, the driver & software simply “capture” the data from the analog-to-digital converter and sends it to the hard drive. (The driver might also do some resampling, but unless you are doing professional recording that shouldn’t matter.)

You were supposed to complain that you couldn’t get any of them to work right.

I tried last DirectSound last night (I had previously done 3 or 4 with MME). While monitoring via Audacity / PC jack, I noticed some skipping and the occasional click. (Is that heading in the right direcion, Koz ?) However, on playback of the Audactity project, recording was fine. I’ll try WASAPI this am.

Aha! When I try WASAPI, the actual record device does not show up - just a bunch of loopbacks. So I check manual and dimly understand I have to select the computer playback device and control volume through that. However, even with vol on the PC speaked audio channel turned right down, the recorded volume is right up at the top. So back to DirectSound to see if I get the skip/click on monitor again.

In Audacity, WASAPI is for recording what is playing on your computer (that’s what the “loopback” means).

In Win Vista and later, DirectSound is not directly implemented, it is a software emulation.

Unless you have a good reason not to, I’d suggest sticking with MME for recording your cassettes.

I agree, but MME is also emulated over WASAPI as far as I know.

DirectSound was designed to have direct kernel access under XP, so tends to have more latency on Vista and later than it did on XP.


Why not try recording through a nightly Alpha build (http://gaclrecords.org.uk/win-nightly/) which has WDM+KS support with no latency? I have been using these builds for 2 months now. They work fine on my PC.

Be aware there is a small risk that WDM-KS could freeze or crash your computer. It’s mostly a problem with some Realtek devices that have HDMI inputs and outputs. That risk is the main reason WDM-KS is not in current releases.


I use it that way for recording what’s playing on the computer - but it also works well recording from my external USB soundcard - it is now my standard host-of-choice.


So when using alpha builds you prefer it to WDM-KS?

My impression is that WASAPI non-loopback is more buggy than WDM-KS non-loopback. It is perhaps easier to get error opening with WDM-KS if some other application is using the sound device.


Absolutely - that’s why I said it was my “host-of-choice” - and that’s after extensive testing - and using alpha+WASAPI for a lot of production work.

Nah, WDM-KS falls over in the dust most times on my on-board Realtek card.


That is not my experience or Robert2’s, as far as I know.

“Falls over in the dust” is not a useful bug report. I suggest you repost details to the -quality list, bearing in mind that WDM-KS lets applications take exclusive control of the sound device.


Gale, I posted a very detailed report to -quality some time back - you said you had not seen that after I posted yesterday asking in WDM-KS would be in 2.1.0 - so I then re-sent that to -quality. Have you still not seen that?


You said your report was “recent”, but it was not in the front page on Nabble.

Anyway, I see you updated your post of November 13th now, thanks.


I am not sure this will be of any use to anybody, but this thread gave me an incentive to test WDM-KS vs. WASAPI in Audacity 2.1.0 Alpha.

I first read the following articles which were enlightening to me:

Windows driver API basics
Understanding The Windows Sound System

Now, on my Windows 8.1 64-bit system with Realtek “integrated audio” (GIGABYTE Z77-DS3H), I can record any input through either WDM-KS or WASAPI: streaming online radio, CD playback, Foobar output from a local FLAC file, microphone.

A funny thing: I can deactivate the Windows “Stereo mix” device in the Windows Sound Control panel when I record through WDM-KS. But even then, I still need to select “Stereo mix” in Audacity to record real sound.

Problems arise when I want to listen to what has just been recorded using the Audacity “Play” button. If, for example, streaming online radio is paused or stopped but still potentially available, Audacity cannot playback the Project if WDM-KS is the Audio Host (“Error while opening sound device”). On the other hand, if I change the Audio Host to WASAPI, playback becomes possible. I can even listen to a mix of the Audacity Project playback and the unpaused radio stream!

Gale mentioned the fact that WDM-KS had problems with HDMI on some systems. I normally output sound to external speakers on my PC through a standard stereo jack. This time, I tried outputting audio to the monitor inbuilt speakers. They get audio through a HDMI cable. This made WDM-KS completely unusable in Audacity (“Error while opening sound device”). I could no longer record anything, not even through WASAPI. I tried deactivating the HDMI speakers and restoring the external speakers. I tried rebooting after uninstalling and reinstalling Audacity. I tried tweaking the Windows Sound settings. To no avail. In the end, I uninstalled, then reinstalled the motherboard audio driver. This did the trick: Audacity and WDM-KS could work together again.

I won’t use these HDMI speakers any more!