[alsa-devel] [PATCH 2/2] Add "cval->res = 384" quirk for Logitech Webcam C600

[Raymond Yau]

2011/3/10 Alexey Fisher <bug-track at fisher-privat.net>

> One more affected devices: Logitech Webcam C600 (046d:0808)
>
> Volume range before quirk is 6400, after (also real) is 16.
>
> Signed-off-by: Alexey Fisher <bug-track at fisher-privat.net>
> ---
>  sound/usb/mixer.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
>
> diff --git a/sound/usb/mixer.c b/sound/usb/mixer.c
> index eba8ae8..c549522 100644
> --- a/sound/usb/mixer.c
> +++ b/sound/usb/mixer.c
> @@ -1122,6 +1122,7 @@ static void build_feature_ctl(struct mixer_build
> *state, void *raw_desc,
>                }
>                break;
>
> +       case USB_ID(0x046d, 0x0808):
>        case USB_ID(0x046d, 0x0809):
>        case USB_ID(0x046d, 0x0991):
>        /* Most audio usb devices lie about volume resolution.
> --
> 1.7.1
>
>
It is because each step of usb audio is 1/256dB  , so 384 step is 1.5dB

Is there any way to verify the resolution is 1.5dB ?

since alsamixertest does not check the capture volume (only check the
playback volume)

And mindB +18dB and maxdB +30dB  ,  It can still record sound using audacity
at +18dB , so it seem break the pulseaudio developer 's assumption that 0%
is -infinite dB


state.U0x46d0x992 {
    control.1 {
        iface MIXER
        name 'Mic Capture Switch'
        value false
        comment {
            access 'read write'
            type BOOLEAN
            count 1
        }
    }
    control.2 {
        iface MIXER
        name 'Mic Capture Volume'
        value 3072
        comment {
            access 'read write'
            type INTEGER
            count 1
            range '0 - 3072'
            dbmin 1800
            dbmax 3000
            dbvalue.0 3000
        }
    }
}