Hi Chris. What does MacOs think about that change?
From: wdmaudiodev-bounce@xxxxxxxxxxxxx <wdmaudiodev-bounce@xxxxxxxxxxxxx>
Date: Wednesday, April 21, 2021 at 5:23 AM
To: wdmaudiodev@xxxxxxxxxxxxx <wdmaudiodev@xxxxxxxxxxxxx>
Subject: [wdmaudiodev] Re: Asynchronous sink feedback question
Thanks Wade but I must be missing something because 5.12 seems fairly clear to
me that Ff on a high speed endpoint should be samples per microframe?
The standard says (5.12 Special Considerations for Isochronous Transfers):
"Note: The examples in this section describe USB for an example involving
full-speed endpoints. The
general example details are also appropriate for high-speed endpoints when
corresponding changes are
made; for example, frame replaced with microframe, 1 ms replaced with 125 μ s,
rate adjustments made
between full-speed and high-speed, etc."
Then every reference to frame in the Feedback section is written as (micro)frame
"Ff is expressed in number of samples per (micro)frame. The Ff value consists
of an integer part that
represents the (integer) number of samples per (micro)frame and a fractional
part that represents the
“fraction” of a sample that would be needed to match the sampling frequency Fs
to a resolution of 1 Hz or
better."
I read the section on implicit feedback for asynchronous sinks
(5.12.4.3<http://5.12.4.3> Implicit Feedback):
"One or more asynchronous sink endpoints are accompanied by an asynchronous
source endpoint. The
data rate on the source endpoint can be used as implicit feedback information
to adjust the data rate on
the sink endpoint(s)."
I have an asynchronous sink endpoint and an asynchronous source endpoint in the
same interface so I simply removed the explicit feedback endpoint:
[1]0004.0108::04/21/2021-08:35:06.229 [USBAudio2](0x0101): AS interface with
bInterfaceNumber=0x01 bAlternateSetting=0x01 uses asynch synchronization but
does not implement a feedback endpoint
[1]0004.0108::04/21/2021-08:35:06.229 [USBAudio2](0x01): Create failed
NTSTATUS=C0440025
That suggests usbaudio2.sys does not look to implement implicit feedback. Is
that right?
Regards
Chris
On 20/04/2021 17:42, Wade Dawson wrote:
I’ve been confused by that as well. The fraction is relative to frame (1ms)
not microframe (125uS), so 48 is correct. I’m fairly certain the Windows UAC2
driver will do implicit feedback, no? I.e., no feedback EP? The osx driver
does for sure.
-Wade.
From: wdmaudiodev-bounce@xxxxxxxxxxxxx<mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx>
<wdmaudiodev-bounce@xxxxxxxxxxxxx><mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx>
Date: Tuesday, April 20, 2021 at 10:09 AM
To: wdmaudiodev@xxxxxxxxxxxxx<mailto:wdmaudiodev@xxxxxxxxxxxxx>
<wdmaudiodev@xxxxxxxxxxxxx><mailto:wdmaudiodev@xxxxxxxxxxxxx>
Subject: [wdmaudiodev] Asynchronous sink feedback question
My understanding of the USB 2.0 spec (section 5.12.4.2
Feedback)<http://sdpha2.ucsd.edu/Lab_Equip_Manuals/usb_20.pdf> for asynchronous
sinks was that the sink in high speed mode should provide feedback of Ff
formatted as a 16.16 number where Ff is the number of samples per _micro_ frame
(125us period).
A 48kHz sink will then return values close to 6.0 (0x00060000 in 16.16 format).
We implemented this and tested some time ago on Windows 10 1903 (or similar).
Testing with Windows 10 20 2H we're seeing audio glitches.
Event logs tell us that the driver is ignoring the feedback values because
they're out of range:
[0]0004.01C4::04/20/2021-13:36:16.321 [USBAudio2]feedback value 0x00062000 is
out of range [0x002f0000,0x00310000], ignoring value
[0]0004.01C4::04/20/2021-13:36:16.321 [USBAudio2]feedback value 0x0005e000 is
out of range [0x002f0000,0x00310000], ignoring value
[0]0004.01C4::04/20/2021-13:36:16.321 [USBAudio2]feedback value 0x00062000 is
out of range [0x002f0000,0x00310000], ignoring value
[0]0004.01C4::04/20/2021-13:36:16.321 [USBAudio2]feedback value 0x00062000 is
out of range [0x002f0000,0x00310000], ignoring value
It appears the driver wants a value close to 48.0 which would be samples per
frame instead of samples per micro frame.
Have I misinterpreted the spec?
I didn't investigate to this detail on the previous release of Windows. I can
see this is a new release of usbaudio2.sys. Is this a new check?
I have tried reporting samples per frame and the glitches stop on Windows 10
but MacOS then glitches.
Any hints gratefully received!
Regards
ChrisHi Chris.
