[wdmaudiodev] Re: Capture with USBAudio under Windows 7 noisy
- From: "Jeff Pages" <jeff@xxxxxxxxxxxxxxxx>
- To: <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Fri, 23 Jul 2010 14:34:55 +1000
Hi Frank,
I first raised it here on the 14th May 2007, and Hakon Strande replied:
>Vista RTM shipped with a float-int conversion bug where we truncate instead
of rounding.
>This could be the cause of what you are seeing. Please tests with SP1 beta
when it ships
>(no, I don't know when that is) to see if this has been addressed with
those bits. If not, please report back.
After SP1 was released, I tested it and found the problem was still
occurring, so I sent another query on the 7th December 2007. Hakon replied,
asking for more information, but for some reason his reply ended up in my
spam folder and I didn't see it until I was clearing it out some six months
later. I e-mailed him off-list then (29th May 2008) but didn't hear back.
In August 2008 Andrew Elder asked about Vista's SRC quality and on the 5th
September I replied with a link to some screen shots showing the artefacts I
was observing (the link is
http://www.innescorp.com.au/uploads/downloads/other/vistacapturesrc.pdf),
but the discussion fizzled out soon after that.
So far it hasn't been anything more than a curiosity for us, as none of our
customers have complained yet, but I keep raising it whenever the subject of
SRCs comes up in the hope that maybe eventually there'll be a solution.
Jeff
-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Frank Yerrace
Sent: Friday, 23 July 2010 2:08 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Capture with USBAudio under Windows 7 noisy
Yes you are correct about WASAPI's IAudioClient::Initialize.
Jeff- just curious- when you reported the problems, how did you go about
reporting them, and approximately when?
-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Jeff Pages
Sent: Thursday, July 22, 2010 7:18 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Capture with USBAudio under Windows 7 noisy
Doesn't the IAudioClient::Initialize function in WASAPI require in shared
mode that the sampling rate be the same as what the audio engine is set to,
or in exclusive mode be a rate that the hardware supports, so that the
Windows SRC is never invoked?
In any case, WASAPI isn't supported on XP, so the applications our customers
are using are unlikely to be using that API for a long time to come. What do
we tell them when they start complaining about capture artefacts on Windows
7?
Jeff
-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Larry Osterman
Sent: Friday, 23 July 2010 12:06 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Capture with USBAudio under Windows 7 noisy
Sure - use WASAPI for capture - that will use the same resampler as is used
for output.
DSound uses the same resampler, but when capturing mono inputs, because
DSound is primarily a game API, it tunes the resampler for performance, not
fidelity (I don't know if there are knobs to make the DSound resampler
operate at a higher fidelity).
Larry
-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Jeff Pages
Sent: Thursday, July 22, 2010 6:47 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Capture with USBAudio under Windows 7 noisy
The applications I've used include Cooledit and Adobe Audition, as well as a
spectrum analyser program I wrote which used the wave API. On XP I believe
capture always used the "best" converter regardless of API, and I don't see
the problem on that platform (all the converter artefacts are below -96dB).
Is there any way in Vista or Windows 7 to force it to use a better quality
converter on capture?
Jeff
-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Larry Osterman
Sent: Friday, 23 July 2010 11:29 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Capture with USBAudio under Windows 7 noisy
What API are you using to capture? It's possible that you're using one of
the lower quality resamplers in the box (for instance if you're using the
wave APIs, I believe you'll use the ACM resampler which is basically the
same resampler used in XP).
Larry
-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Jeff Pages
Sent: Thursday, July 22, 2010 4:20 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Capture with USBAudio under Windows 7 noisy
Tim wrote:
>The purists might disagree, but it has been my experience that the
>Windows sample rate converter is pretty good for most purposes. How
>are you detecting the noise at 4 kHz? Are you injecting a pure signal
>and doing a spectrum analysis on the result?
While the render sampling rate converter in Windows 7 is very good, the
capture converter is a different matter entirely. It has conversion
artefacts at about -65dB on a pure tone. I first noticed this back when
Vista was released and tried reporting it a couple of times but got nowhere,
and the problem has persisted into Windows 7.
Jeff
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