[PATCH v2] ALSA: usb-audio: Fix microphone sound on HD webcam.

[Takashi Iwai]

On Thu, 18 Jul 2024 08:07:56 +0200,
wangdicheng wrote:
> 
> I own an external usb Webcam, HD webcam, which had low mic volume and
> inconsistent sound quality. Video works as expected.
> 
> (snip)
> [   95.473820][ 1] [   T73] usb 5-2.2: new high-speed USB device number 7 using xhci_hcd
> [   95.773974][ 1] [   T73] usb 5-2.2: New USB device found, idVendor=1bcf, idProduct=2281, bcdDevice= 0.05
> [   95.783445][ 1] [   T73] usb 5-2.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> [   95.791872][ 1] [   T73] usb 5-2.2: Product: HD webcam
> [   95.797001][ 1] [   T73] usb 5-2.2: Manufacturer: Sunplus IT Co
> [   95.802996][ 1] [   T73] usb 5-2.2: SerialNumber: 20200513
> [   96.092610][ 2] [ T3680] usb 5-2.2: Warning! Unlikely big volume range (=4096), cval->res is probably wrong.
> [   96.102436][ 2] [ T3680] usb 5-2.2: [5] FU [Mic Capture Volume] ch = 1, val = 0/4096/1
> 
> Set up quirk cval->res to 16 for 256 levels,
> Set GET_SAMPLE_RATE quirk flag to stop trying to get the sample rate.
> Confirmed that happened anyway later due to the backoff mechanism,
> After 3 failures.
> 
> All audio stream on device interfaces share the same values,
> apart from wMaxPacketSize and tSamFreq :
> 
>       bLength                 9
>       bDescriptorType         4
>       bInterfaceNumber        3
>       bAlternateSetting       4
>       bNumEndpoints           1
>       bInterfaceClass         1 Audio
> 
> Interface Descriptor:
>   bLength                 9
>   bDescriptorType         4
>   bInterfaceNumber        3
>   bAlternateSetting       4
>   bNumEndpoints           1
>   bInterfaceClass         1 Audio
>   bInterfaceSubClass      2 Streaming
>   bInterfaceProtocol      0
>   iInterface              0
>   AudioStreaming Interface Descriptor:
>     bLength                 7
>     bDescriptorType        36
>     bDescriptorSubtype      1 (AS_GENERAL)
>     bTerminalLink           3
>     bDelay                  1 frames
>     wFormatTag         0x0001 PCM
>   AudioStreaming Interface Descriptor:
>     bLength                11
>     bDescriptorType        36
>     bDescriptorSubtype      2 (FORMAT_TYPE)
>     bFormatType             1 (FORMAT_TYPE_I)
>     bNrChannels             1
>     bSubframeSize           2
>     bBitResolution         16
>     bSamFreqType            1 Discrete
>     tSamFreq[ 0]        48000
>   Endpoint Descriptor:
>     bLength                 9
>     bDescriptorType         5
>     bEndpointAddress     0x86  EP 6 IN
>     bmAttributes            5
>       Transfer Type            Isochronous
>       Synch Type               Asynchronous
>       Usage Type               Data
>     wMaxPacketSize     0x0064  1x 100 bytes
>     bInterval               4
>     bRefresh                0
>     bSynchAddress           0
>     AudioStreaming Endpoint Descriptor:
>       bLength                 7
>       bDescriptorType        37
>       bDescriptorSubtype      1 (EP_GENERAL)
>       bmAttributes         0x01
>         Sampling Frequency
>       bLockDelayUnits         0 Undefined
>       wLockDelay         0x0000
> (snip)
> 
> Testing patch provides consistent good sound recording quality and volume range.
> 
> (snip)
> [   95.473820][ 1] [   T73] usb 5-2.2: new high-speed USB device number 7 using xhci_hcd
> [   95.773974][ 1] [   T73] usb 5-2.2: New USB device found, idVendor=1bcf, idProduct=2281, bcdDevice= 0.05
> [   95.783445][ 1] [   T73] usb 5-2.2: New USB device strings: Mfr=1, Product=2, SerialNumber=3
> [   95.791872][ 1] [   T73] usb 5-2.2: Product: HD webcam
> [   95.797001][ 1] [   T73] usb 5-2.2: Manufacturer: Sunplus IT Co
> [   95.802996][ 1] [   T73] usb 5-2.2: SerialNumber: 20200513
> [   96.110630][ 3] [ T3680] usbcore: registered new interface driver snd-usb-audio
> [   96.114329][ 7] [ T3677] usb 5-2.2: Found UVC 1.00 device HD webcam (1bcf:2281)
> [   96.167555][ 7] [ T3677] usbcore: registered new interface driver uvcvideo
> 
> Signed-off-by: wangdicheng <wangdicheng at kylinos.cn>
> ---
> V1 -> V2: align the space,Update code to v6.8-rc3,and make modifications based on it

Just one minor issue: the mail address of your Signed-off-by is
different from the From address.  Try to make them consistent.


thanks,

Takashi