[alsa-devel] @Daniel Mack: Send you a FTU

Felix Homann linuxaudio at showlabor.de
Tue Jun 14 13:37:53 CEST 2011

Hi Daniel,

(just to have it public on the list)

Am 14.06.2011 10:56, schrieb Daniel Mack:
> Quite frankly, I'm not fully aware about known issues with these
> devices that need attention. Could you summarize which problems are
> left to look at?

Here's a list of the issues I'm aware of:

1. Playback clicks:

There are periodic clicks in the playback at all sample rates. They are 
not very noticable in normal use but when you playback a plain sine the 
clicks are very obvious. When we discussed it last year we suspected 
that the device uses "implicit feedback". For the record: When we used 
the device with QUIRK_AUDIO_STANDARD_INTERFACE quirks we had clickless 
playback at 48 kHz and 96 kHz, but playback at 44.1 kHz and 88.2 kHz was 
totally distorted and the kernel would eventually crash after a minute 
or so.

2. External clock sync

The FTU devices are capable of syncing to an external clock via SPDIF. I 
don't know how to switch between internal and external clock. I don't 
even have a second audio interface to test with.

3. Mixer control steps:

The mixer controls are working fine now but are very fine grained. Being 
that fine grained it is hard to control the mixer in some mixer programs 
like alsamixer (alsamixer-qt4 and gamix work fine). A little bit of fine 
tuning would be nice. But I don't know which step size the hardware 
actually supports.

4. Reverb unit:

The FTU devices have a reverb unit which isn't supported, yet. It's 
straight forward based on the basic mixer support . I've almost got it 
wroking except for the "Reverb Program" switch. I know how to do it, so 
probably there will be a patch soon.

5. "Lost" URBs:

Some users reported occasional playback distortion combined with dmesg 
output like this: "ALSA urb.c:480: frame 5 active: -18". I don't know if 
this is really related to the driver. Actually I don't think so but who 
knows ...

Are there any other issues?

Kind regards,


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