[alsa-devel] Duet Firewire

[Takashi Sakamoto]

Hi,
(C.C.ed to alsa-devel)

On Sun, Feb 16, 2020 at 03:52:27AM +0000, roberto lopez torres wrote:
> Hi, i just got a Duet Firewire, and i'm trying to make it work with 5.3.0-29-gen
> eric #31-Ubuntu
> 
>    I have inputs and outputs from the interface but can't config anything
>    at the moment, and i got a noise every 16 seconds on headphones
>    monitoring.
> 
>    I'm pretty new using linux.

The ALSA support for Apogee Duet FireWire starts at Linux kernel v4.21.
As you can see, the support is just for packet streaming, thus it's just
possible to transmit/receive PCM frames and MIDI messages. However, the
device is designed to run just depending on its internal clock (e.g.
47994 frames/sec), thus at present it generates periodical noise since
the ALSA driver is designed to transmit just the same number of PCM
frames as sampling rate (e.g. 48000 frames/sec).

The support of any control is expected to be implemented in userspace
application. This is the reason that you can see no elements in ALSA
control application (e.g. alsamixer). However, the protocol to control
the device is not clear yet. As long as I know, it's complicated and
requires the batch of codes for the application. This is the reason
that ALSA in-kernel driver doesn't have the code.


Regards

Takashi Sakamoto