Re: Motu 896Mk3Hybrid dump

[Takashi Sakamoto <o-takashi@sakamocchi.jp>]

Hi,

On Mon, Feb 06, 2023 at 06:30:44PM +0100, M. Armsby wrote:
> Hi there Takashi,
> 
> please send me your instructions.
> 
> I will do everything to get these MOTU devices working properly.
 
Okay. As a first step, would I ask you to build `linux-firewire-utils`?

 * https://github.com/cladisch/linux-firewire-utils

In the top level of directory, execute below commands:

$ autoreconf -i
$ ./configure
$ make

When building successfully, you can find `firewire-request` in `src`
directory. It is useful to read the status of device and required for
our investigation.

Before building, I think you need to install some package required for
the work (e.g. compiler), but I'm not Manjaro user so contact to Manjaro
user to ask it...

> The problem with device allocation is this:
> 
> Ardour and Reaper see the ALSA driver and automatically choose 1+2
> for main stereo out.
> 
> But - there is no connection.
> 
> If I choose 3+4 then Motu hardware actually gets sound output on 1+2
> 
> That means all Motu outs are shifted by 2 in the Linux protocol.
> 
> This is true for Traveler MK1 and MK3 so I assume it is an error in
> all snd_motu_spec
> 
> I made a short video demonstrating this.
> 
> https://www.transfernow.net/dl/20230206jG0fet84/OFRBRajr

Thanks for your taking and uploading the video.

The below figure illustrates your cases:

 ++======================++    +-------+    ++===============++
 ||       Traveler       ||    | frame |    ||  Application  ||
 ||                      ||    |       |    ||               ||
 || headphone output 1/2 || <- |  0/1  | <- ||  Output 1/2   ||
 || analog output 1/2    || <- |  2/3  | <- ||  Output 3/4   ||
 || analog output 3/4    || <- |  4/5  | <- ||  Output 5/6   ||
 || analog output 5/6    || <- |  6/7  | <- ||  Output 7/8   ||
 || analog output 7/8    || <- |  8/9  | <- ||  Output 9/10  ||
 || AES/EBU (XLR) 1/2    || <- | 10/11 | <- ||  Output 11/12 ||
 || S/PDIF (opt) 1/2     || <- | 12/13 | <- ||  Output 13/14 ||
 ++======================++    +-------+    ++===============++

I note that the effective source of headphone output is selectable
between the above 7 pairs. Additionally, when enabling ADAT optical
output, 8 channels are newly added to the frame thus 22 channels are
available in a view of application.

Well, inconveniently to you, the above mapping is expected. ALSA
firewire-motu driver passes no information to the application about
what the channel of frame is assigned to, due to technical reason of
ALSA interface to user space application. As a result, the application
just enumerates audio sample in its order.


Regards

Takashi Sakamoto