[LAU] Problems with sample rate and recordings (Mackie onyx > 1640-i < Firewire > Debian )

[Chris Caudle]

On Tue, March 3, 2015 2:58 am, sub wrote:
> Where do you get that information [hardware sample rate] from? Jackctl?

Jackctl (I assume you mean qjackctl application?) is just passing through
the information from the jack server.  You can see most easily by watching
the output on the command line when starting jack by hand, but qjackctl
also has a method to display the output by clicking on the "Messages"
button to display the output from the server.

This is an example output from a jack instance I just started:
Tue Mar  3 14:47:03 2015: Acquired audio card Audio1
Tue Mar  3 14:47:03 2015: creating alsa driver ...
hw:M2496|hw:M2496|1024|2|44100|0|0|nomon|swmeter|-|32bit
Tue Mar  3 14:47:03 2015: configuring for 44100Hz, period = 1024 frames
(23.2 ms), buffer = 2 periods
Tue Mar  3 14:47:03 2015: ALSA: final selected sample format for capture:
32bit integer little-endian
Tue Mar  3 14:47:03 2015: ALSA: use 2 periods for capture
Tue Mar  3 14:47:03 2015: ALSA: final selected sample format for playback:
32bit integer little-endian
Tue Mar  3 14:47:03 2015: ALSA: use 2 periods for playback

This is the line which describes the attempt to set the hardware
configuration:

configuring for 44100Hz, period = 1024 frames (23.2 ms), buffer = 2 periods

This is the output from the qjackctl message window when I select 192k

Tue Mar  3 14:57:15 2015: Acquired audio card Audio1
Tue Mar  3 14:57:15 2015: creating alsa driver ...
hw:M2496|hw:M2496|1024|2|192000|0|0|nomon|swmeter|-|32bit
Tue Mar  3 14:57:15 2015: configuring for 192000Hz, period = 1024 frames
(5.3 ms), buffer = 2 periods
Tue Mar  3 14:57:15 2015: ALSA: final selected sample format for capture:
32bit integer little-endian
Tue Mar  3 14:57:15 2015: ALSA: use 2 periods for capture
Tue Mar  3 14:57:15 2015: ALSA: final selected sample format for playback:
32bit integer little-endian

That interface card does not actually support 192k sample rate, so 96k was
chosen as the closest available rate, but that was not actually displayed
in the messages window.  The qjackctl status window did however show the
actual sample rate being used.

creating alsa driver ...
hw:M2496|hw:M2496|1024|2|192000|0|0|nomon|swmeter|-|32bit
configuring for 192000Hz, period = 1024 frames (5.3 ms), buffer = 2 periods
ALSA: final selected sample format for capture: 32bit integer little-endian

The jack_samplerate application can be used to display the currently used
samplerate of the running server:
$ jack_samplerate
96000

So not quite as simple as it could be, it would be nicer if the jackd
server actually printed to the console the chosen sample rate, but you
have to get a jack client such as jack_samplerate or qjackctl to display
the running sample rate for you.



-- 
Chris