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

[Javier Vasquez]

On Sun, Jul 1, 2012 at 11:31 AM, Javier Vasquez <j.e.vasquez.v at gmail.com> wrote:
> Hi,
>
> 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_hda_codec_hdmi,snd_hda_codec_idt,snd_hda_intel
> 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
> snd_hwdep,snd_timer,snd_hda_codec_hdmi,snd_hda_codec_idt,snd_pcm,snd_hda_codec,snd_hda_intel
> 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), :-)

Forgot to mention that the "arecord | aplay" introduces a weird echo,
so that's why I was looking to avoid using it, :-)  I played around
with "--disable-resample" and the rate, but I always got the echo.
When music sounds, the resulting mix can be bared.  When the sound is
people talking, then it's hard to understand, :-)

-- 
Javier.