[linux-audio-user] debugging usb audio (silence from imic)

[Anthony Baxter]

I've plugged a Griffin imic into my Dell 5150 (running FC3-ish). The machine
recognised the card and modprobe snd-usb-audio, followed by alsamixer -c 1,
showed the card. I can set and get the settings and the like all fine. The
one thing I _can't_ get out is audio. None at all. 

aplay -device=hw:1,0 foofile.wav seems to run fine, except for the bit where
it puts out sound. I've not got anything muted in alsamixer that I can see. 

This is kernel 2.6.8-1.541. (Hopefully) relevant bits from /proc/asound:

bonanza# ls
card0  cards    I82801DBICH4  oss  seq     timers
card1  devices  modules       pcm  system  version
bonanza# cat cards
0 [I82801DBICH4   ]: ICH - Intel 82801DB-ICH4
                     Intel 82801DB-ICH4 at 0xf4fff800, irq 7
1 [system         ]: USB-Audio - iMic USB audio system
                     Griffin Technology, Inc iMic USB audio system at 
usb-0000:00:1d.0-1, full speed
bonanza# cat version  
Advanced Linux Sound Architecture Driver Version 1.0.6 (Sun Aug 15 07:17:53 
2004 UTC).
Compiled on Sep  1 2004 for kernel 2.6.8-1.541.
bonanza# cd card1
bonanza# ls
id  oss_mixer  pcm0c  pcm0p  stream0  usbbus  usbid
bonanza# cat id
system
bonanza# cat stream0     # during 'aplay --device=hw:1,0 fooofile.wav'
Griffin Technology, Inc iMic USB audio system at usb-0000:00:1d.0-1, full 
speed : USB Audio

Playback:
  Status: Running
    Interface = 1
    Altset = 2
    URBs = 5 [ 4 4 4 4 4 ]
    Packet Size = 200
    Momentary freq = 44100 Hz
  Interface 1
    Altset 1
    Format: S16_LE
    Channels: 1
    Endpoint: 1 OUT (ADAPTIVE)
    Rates: 6400 - 48000 (continuous)
  Interface 1
    Altset 2
    Format: S16_LE
    Channels: 2
    Endpoint: 1 OUT (ADAPTIVE)
    Rates: 6400 - 48000 (continuous)

Capture:
  Status: Stop
  Interface 2
    Altset 1
    Format: S8
    Channels: 1
    Endpoint: 4 IN (SYNC)
    Rates: 6400 - 48000 (continuous)
  Interface 2
    Altset 2
    Format: S16_LE
    Channels: 1
    Endpoint: 4 IN (SYNC)
    Rates: 6400 - 48000 (continuous)
  Interface 2
    Altset 3
    Format: S16_LE
    Channels: 2
    Endpoint: 4 IN (SYNC)
    Rates: 6400 - 48000 (continuous)


bonanza# lsmod | egrep 'snd|sound'
snd_intel8x0           29709  0 
snd_usb_audio          55457  1 
snd_usb_lib            10305  1 snd_usb_audio
snd_ac97_codec         61329  1 snd_intel8x0
snd_pcm_oss            42361  0 
snd_mixer_oss          14529  1 snd_pcm_oss
snd_pcm                84681  3 snd_intel8x0,snd_usb_audio,snd_pcm_oss
snd_timer              25413  1 snd_pcm
gameport                3777  1 snd_intel8x0
snd_mpu401_uart         7233  1 snd_intel8x0
snd_rawmidi            21733  2 snd_usb_lib,snd_mpu401_uart
snd_seq_device          6217  1 snd_rawmidi
snd                    44709  11 
snd_intel8x0,snd_usb_audio,snd_ac97_codec,snd_pcm_oss,snd_mixer_oss,snd_pcm,snd_timer,snd_mpu401_uart,snd_rawmidi,snd_seq_device
soundcore               7457  1 snd
snd_page_alloc          6985  2 snd_intel8x0,snd_pcm


One thing I've noticed is that lsmod is telling me that the snd_usb_audio
device is being used, but it's not saying _what_ it's being used by. I can't
see any processes running that have anything in /dev/snd open. 

I'd love to get some tips on where to look next for continuing to debug this -
one of my own projects is shtoom (a voip phone) and I'm always getting
pleas for help with ALSA - it'd be excellent if I knew a bit more about what
I'm doing here so I can help them in turn <wink>

Thanks,
Anthony