So I have reverted to native Jack and all is well on my tower system.
However, my laptop, which I use for quick sketches using RG and Qsynth,
has a sound card (Realtek ALC294) that only allows 48kHz sample rate.
If I use aplay on a 44.1kHz file it plays back about a tone too high.
This can be sorted out by using alsa's plugin pcm device (plughw:0,0) which
does the sample rate conversion. However, Jack also runs at 48kHz and
although RG seems to cope fine with this (doing its own conversion) it
occurred to me to try to run Jack over the alsa plugin pcm too. But Jack
does not like this! It does not allow you to set --rate 44100 --period
256 e.g.
Now, after a day's mucking about, I have discovered that it is possible to
have Jack run at 44.1kHz by using its 'dummy' device and connecting it
to the card via the 'alsa_in' and 'alsa_out' tools and to RG and Qsynth
using
'jack_connect' or 'Qjackctl'.
Now the alsa tools do the sample conversion. Great, but it is a bit of a
faff.
So, my questions are:
a) Can Jack be made to use the alsa plugin pcm and if not, why not?
b) Is there any point in trying to move the sample conversion to earlier
in the
chain or is it all done in hardware anyway?
'just curious!
TIA
Chuck.
On 13/08/2025 05:18, Ted Felix wrote:
No, that makes no sense. I use JACK (not pipewire) at 44,100 and I
have no problems.
Sample rate conversion is trivial on modern hardware. I would leave
things at 48,000 and ignore the warnings.
You might want to try reconfiguring pipewire's sample rate via its
jack.conf file and maybe pipewire.conf. Setting both to 44,100 might
fix everything. I don't think pw-metadata is the best approach since
that changes things while they are running and I believe it loses your
settings when you shut down. The .conf files change things at startup
and should be more reliable.
Pipewire is too buggy for my tastes. I avoid. JACK is 100% solid.
Ted.
On 8/11/25 7:11 AM, chuck elliot wrote:
I have a piece which contains both midi and audio segments.
When I open the 'Manage Audio Files' dialog, there is a warning
about sample rate mismatches between files (44100Hz) and Jack (48000Hz).
These actually play fine but I assume that things would be better if
I adjust
Jack's settings to match the files, so I do so using "pw-metadata -n
0 clock.force-rate 41000".
(I am using Pipewire's Jack implementation).
Now RG is happy but there is horrendous latency and the audio is
sometimes seconds behind the midi output (CPU=~23%).
This doesn't make sense.
Does it?
TIA,
Chuck.
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