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Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

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Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

PostPosted: Sat Dec 05, 2020 4:51 pm
by dfira
I do not have a listening environment at all at the moment. but I decided to test the noise floor of my Focusrite Scarlett Solo 3rd Gen with nothing plugged in,

I recorded exactly 5 seconds of audio into Audacity then used its built-in RMS analyzer plugin to measure the level.

Windows:
MME: -84.437 dB
DirectSound: -84.437 dB
WASAPI: -78.786 dB
Linux:
ALSA: -78.786 dB
JACK (computer began chirping when started): -78.786 dB

Have I done something wrong? Are MME/DirectSound applying some kind of filter or accidental filter effect is occurring? Or are they just superior sonically?

Re: Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

PostPosted: Sat Dec 05, 2020 5:32 pm
by merlyn
It's the signal to noise ratio that's important, isn't it? You'd need a test signal to be able to say what's going on.

(1) If the Focusrite control panel is involved that could be changing the gain. On ALSA the control panel isn't used. You may get some controls with alsamixer. Type this into a terminal :

Code: Select all
$ alsamixer

(2) Depending on what kernel you have there may be issues with Gen 3 Scarletts and ALSA/JACK.

Re: Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

PostPosted: Sat Dec 05, 2020 5:56 pm
by dfira
Right, I don't think any of those factors were applicable in my tests, notice how the noise under Linux is exactly the same as WASAPI, and my tests in Windows, all I did was select from the dropdown menu in Audacity. No manual changing of Gain at least. Alsamixer i'm pretty sure was at 100%

Re: Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

PostPosted: Sat Dec 05, 2020 6:18 pm
by merlyn
dfira wrote:DirectSound: -84.437 dB
WASAPI: -78.786 dB

That looks like a gain change. What are you proposing is happening? WASAPI randomly flips bits because it feels like it? :)

Re: Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

PostPosted: Sat Dec 05, 2020 8:55 pm
by dfira
Yeah lol. I was thinking maybe increased jitter, or packet loss or something.

I did send two WhatsApp voice messages with a plugged in mic from both the quieter windows and linux, and although WhatsApp compresses stuff, the noisefloor was audibly lower in the windows recordin, whilst my voice stayed the same...

But yeah maybe you're right. Without buying any external gear, what can i do to test this? Hook the output to the input and record a test signal from the computer?

Re: Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

PostPosted: Sun Dec 06, 2020 1:46 pm
by merlyn
You could try a signal generator app on your phone. What you want to do is send the computer the same signal at exactly the same level. The difference in noise is about 6dB so you should see a ~6dB change in the level of the signal too.

Re: Is MME and DirectSound on Windows Performing better than WASAPI and Linux ALSA/JACK??

PostPosted: Sun Dec 06, 2020 2:03 pm
by CS70
MME and Direct sound use 16 bit words (at least unless something's changed lately) and process the signal thru Windows audio (i.e. the windows sound mixer), which depending on the configuration, the OS version and the audio card driver, might add effects. WASAPI exclusive won't.