Re: [PATCH] ALSA: usb-audio: Add quirk for inverted sample rates on NUX NAI-24

[Takashi Iwai <tiwai@suse.de>]

On Sun, 20 Sep 2026 14:26:53 +0200,
Darren Chang wrote:
> 
> The NUX NAI-24 (USB 3703:2000) has a UAC2 clock source that reports
> bmAttributes = 0x01 (internal fixed clock) and bmControls = 0x07, so the
> driver treats its sample rate as programmable.  When the driver sends
> SET_CUR(SAMPLING_FREQ_CONTROL), the firmware acknowledges the request and
> then runs the clock on the opposite base-rate family: asking for 44100 Hz
> makes the device run at 48000 Hz, and asking for 48000 Hz makes it run at
> 44100 Hz.
> 
> The result is playback that is about 8.8% fast, or 8.4% slow with heavy
> static on the 48000 Hz family.  macOS and Windows ignore bmControls, treat
> the clock as fixed and resample, so they are unaffected.
> 
> Work around it by sending the partner rate in SET_CUR for this device, so
> the device runs at the requested rate.  A new QUIRK_FLAG_SWAP_RATES flag
> controls this, applied through the quirk flags table.
> 
> Only the 44.1/48 kHz pair has been verified on hardware; the 88.2/96 kHz
> and 176.4/192 kHz pairs are untested but follow the same pattern.
> 
> Testing: the equivalent change ran on the device as a locally built
> module (44100 Hz PCM, device clock 44100 Hz, no xruns, correct tempo, no
> static).  This upstream form compiles for sound/usb without warnings and
> passes checkpatch, but has not been built in a full kernel tree or
> load-tested.
> 
> Assisted-by: LLM
> Signed-off-by: Darren Chang <darrenchangjr01@gmail.com>

Applied to for-next branch now.  Thanks.


Takashi