[arch-general] [alsa][hda-intel] Not able to loopback sound between line-in (mic) and speakers / line-out (head phones).

Javier Vasquez j.e.vasquez.v at gmail.com
Sun Jul 1 13:31:20 EDT 2012


I'm using a HP EliteBook 8540w laptop.  It comes with following audio card:

00:1b.0 Audio device: Intel Corporation 5 Series/3400 Series Chipset
High Definition Audio (rev 05)
        Subsystem: Hewlett-Packard Company Device 1521
        Flags: bus master, fast devsel, latency 0, IRQ 54
        Memory at d7520000 (64-bit, non-prefetchable) [size=16K]
        Capabilities: <access denied>
        Kernel driver in use: snd_hda_intel

Udev automatically loads the following modules for this card:

% lsmod | 'grep' snd
snd_hda_codec_hdmi     23672  4
snd_hda_codec_idt      55508  1
snd_hda_intel          24053  7
snd_hda_codec          94273  3
snd_hwdep               6300  1 snd_hda_codec
snd_pcm                74958  5 snd_hda_codec_hdmi,snd_hda_codec,snd_hda_intel
snd_page_alloc          7217  2 snd_pcm,snd_hda_intel
snd_timer              18966  3 snd_pcm
snd                    58997  17
soundcore               5410  1 snd

I use plain alsa to handle audio.  Alsa offers for this card
(alsamixer -V all) the following controls:

*  Master                   (unmuted  -  42)
*  Headphone           (unmuted  -  84)
*  Speaker                 (unmuted  -  84)
*  PCM                       (unmuted  -  85)
*  Mic Jack Mode      (Line In)
*  Beep                       (muted      -  0)
*  Capture                  (                    80)
*  Digital                     (                    86)
*  Muted-LED Mode  (Follow Master)
*  Mux                         (                    0)

To make a loopbak between line-in (mic input but configured as
line-in) and any sort of audio out (speakers, line-out/headphones) I
have to do:

% arecord | aplay

Does anyone has this card or similar, and experience the same thing?
I might be mistaken, but I understand through reading different
forums, that this SW loopback using alsa utilities beyond alsamixer
shouldn't be necessary.  Is that right, or it's just that alsa doesn't
offer such capability for this card?  If someone has figured how to
avoid using the "arecord | aplay" loop, please let me know.

BTW, I've played around with the controls, including Mux, and there's
no way I can dispense of "arecord | aplay".  I haven't added
additional modules, like snd-mixer-oss or snd-pcm-oss, but they don't
sound relevant to me at first (might be mistaken though), :-)



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