Mic boost (igain) for uaudio

[Chris Billington]

On 3/11/07, Chris Billington  wrote:
> Hi,
>
> I use a USB audio device (phone handset) for VOIP on 6.2-stable.
>
> The audio from the USB device is really low level- correspondents can
> hardly hear me.
>
> The uaudio0  device appears as /dev/dsp1.0, /dev/dsp1.1, etc:
>
> /dev/dsp1.0     /dev/dsp1.2     /dev/dsp1.4
> /dev/dsp1.1     /dev/dsp1.3     /dev/dsp1.5
>
> dmesg|grep pcm:
>
> dmesg|grep pcm
>   timer: 0x000100ef therm: 0x00010000 err: 0x0001000f pcm: 0x00010000
> pcm0: <Intel ICH6 (82801FB)> port 0xe000-0xe0ff,0xe400-0xe43f mem
> 0xffe3fc00-0xffe3fdff,0xffe3f800-0xffe3f8ff irq 17 at device 30.2 on
> pci0
> pcm0: Reserved 0x200 bytes for rid 0x18 type 3 at 0xffe3fc00
> pcm0: Reserved 0x100 bytes for rid 0x1c type 3 at 0xffe3f800
> pcm0: [MPSAFE]
> pcm0: <Avance Logic ALC655 AC97 Codec (id = 0x414c4760)>
> pcm0: Codec features 5 bit master volume, no 3D Stereo Enhancement
> pcm0: Primary codec extended features reserved 1, center DAC, surround
> DAC, LFE DAC, reserved 5
> pcm0: ac97 codec dac ready count: 0
> pcm0: sndbuf_setmap 1e469000, 4000; 0xd4f49000 -> 1e469000
> pcm0: sndbuf_setmap 1e45f000, 4000; 0xd4f4d000 -> 1e45f000
> pcm0: measured ac97 link rate at 47997 Hz, will use 48000 Hz
> pcm1: <USB audio> on uaudio0
> pcm1: using a default buffer size of 16384 bytes
>
> # cat /dev/sndstat
> FreeBSD Audio Driver (newpcm)
> Installed devices:
> pcm0: <Intel ICH6 (82801FB)> at io 0xffe3fc00, 0xffe3f800 irq 17 bufsz
> 16384 kld snd_ich (1p/1r/4v channels duplex default)
> pcm1: <USB audio> at ? kld snd_uaudio (1p/1r/4v channels duplex)
>
>
> For the onboard audio I can set mic boost on (I think, looking at ac97.c) bu
> # mixer -f /dev/dsp0 igain 100
> Setting the mixer igain from 100:100 to 100:100.
>
> However for the /dev/dsp1 I get:
>
> # mixer -f /dev/dsp1 igain 100
> mixer: unknown device: igain
> usage: mixer [-f device] [-s | -S] [dev [+|-][voll[:[+|-]volr]] ...
>        mixer [-f device] [-s | -S] recsrc ...
>        mixer [-f device] [-s | -S] {^|+|-|=}rec rdev ...
>  devices: pcm, mic
>  rec devices:
>
> The usb audio device appears to mixer (and kmixer, etc) as two output
> channels pcm and mic.
>
> Is there any way to add igain (20dB mic boost) for USB audio?
>
> regards
> Chris
>

To answer my own question, probably no, since there is no such channel
on uaudio like there is in ac97.
I made a small patch to the Twinkle SIP phone app to add 20dB of gain
to the mic channel before it goes to the codec, and audio quality is
now fine.
Chris