Re: kern/55687: Slowed down/noisy recording with audio(4) (probably incorrect sample rate)

[Tetsuya Isaki <isaki%pastel-flower.jp@localhost>]

The following reply was made to PR kern/55687; it has been noted by GNATS.

From: Tetsuya Isaki <isaki%pastel-flower.jp@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: kern-bug-people%netbsd.org@localhost,
	gnats-admin%netbsd.org@localhost,
	netbsd-bugs%netbsd.org@localhost
Subject: Re: kern/55687: Slowed down/noisy recording with audio(4) (probably incorrect sample rate) 
Date: Thu, 01 Oct 2020 21:10:09 +0900

 Thank you for detailed report.
 
 This uploaded WAV file appears to have four channels data like as
 L,R,0,0, L,R,0,0, ... in 48kHz, despite WAV file header says two
 channels 48kHz.
 
 I found that this is because of record source has two inputs at
 the same time on mixerctl.  You will solve it by selecting one
 recording source:
 
  # mixerctl -w record.source={ADC01|ADC02}
 
 I could reproduce it on NetBSD 9.0 and 7.1 hdafg on my laptop,
 so this is not a new problem.
 (And I agree that mixerctl is not user-friendly...)
 
 
 For details:
 In device attachment phase, MD driver(hdafg) reports supported
 hardware formats (including number of channels or frequencies)
 to MI audio layer.  MI layer and MD driver agree it with each
 other.  In this case, MI and MD agree to record on stereo 48kHz.
 But since there are two recording sources on mixerctl, hdafg
 actually transferred four channels 48kHz of data during recording.
 Although I don't know that what benefit or functionality does
 multiple record source selection have, at least hdafg should be
 fixed not to transfer unreported (and not agreed each other)
 format data.
 
 I'm not sure but... should hdafg (or mixerctl?) be able to select
 only one record source at the same time?
 
 Thanks,
 ---
 Tetsuya Isaki <isaki%pastel-flower.jp@localhost / isaki%NetBSD.org@localhost>