[alsa-devel] snd-usb-audio issues??

[Takashi Iwai]

At Mon, 14 Apr 2014 15:26:45 +0200,
Clemens Ladisch wrote:
> 
> Richard Storer wrote:
> >         bTerminalID             4
> >         wTerminalType      0x0603 Line Connector
> 
> >         bDescriptorSubtype      6 (FEATURE_UNIT)
> >         bUnitID                 5
> >         bSourceID               4
> >         bmaControls( 0)      0x02
> >           Volume Control
> 
> That single capture mixer control controls the line input.
> (I don't know why it's labelled as "Mic", or how the device
> switches between mic and line signal levels.)

It comes from live24ext_map[] in mixer_maps.c, introduced via commit
69b1f1e8337fc94a7ea0730588960e82676dc2dc, reading below:

    Author: Timofei Bondarenko <tim at ipi.ac.ru>
    Date:   Tue Oct 30 15:28:14 2007 +0100

    [ALSA] usb-audio - SB Live24-External better handling
    
    This patch improves support for 'SB Live 24-bit Extarnal' USB card.
    1) This card can go into muted state when a headphones connected or
    disconnected. So notify mixer about changes in headphone jack.
    2) Add LED controls and procfs support just as in similar Audigy 2 NX card.
    3) Rename 'PCM Capture' conrol to 'Mic Capture' to reflect reality:
    the card may adjust microphone input level only.


Takashi