Thanks a lot for your reply, Patrick!
I will keep experimenting with different combinations of format settings.

About this:

Do you have a "layer" between the drivers (alsa oss etc...)

I am not sure of what you mean (I am not an expert :) ).
Of course the computer has alsa, but as far as I understand all the software involved (virtual keiboard, QSynth, JACK) are connected directly, without intermediaries.
Can you give me some tests to do, to determine whether there is a layer in between or not?

Again, thanks a lot!

Fabio

On 2022-11-28 13:16, Patrick Pouget wrote:
White noise is, in general, due to format mismatch. I mean data types, sample rate, number of channels etc...

I can see 2 causes
* Jack should be queried for the format by the application. If you have the problem with many, it is not the case
* jack relay on drivers that return wrong informations or no information or a default information. Do you have a "layer" between the drivers (alsa oss etc...) and jack?


On Mon, 2022-11-28 at 09:14 +0100, Patrick Pouget wrote:
White noise is, in general, due to format mismatch. I mean data types, sample rate, number of channels etc...

I can see 2 causes
* Jack should be queried for the format by the application. If you have the problem with many, it is not the case
* jack relay on drivers that return wrong informations or no information or a default information. Do you have a "layer" between the drivers (alsa oss etc...) and jack?



On Mon, 2022-11-28 at 09:03 +0500, Fabio G wrote:
Hello to all!

I am experimenting with audio production under Linux Mint 20.3  (based on Ubuntu 20.04). I managed to install a low latency kernel, then I have installed JACK, and Qsynth, following the steps described in this tutorial:

http://www.tedfelix.com/linux/linux-midi.html

Everything seems to work fine if I use Qsynth and pulseaudio: I use the vmpk simple virtual keyboard, and I have good output sound.

I have also tested JACK, as suggested in the tutorial using


$ jack-play test.wav

and I hear the right clean output.

However, when I tell Qsynth to use JACK, I have a lot of noise. When I hit a key I have "white noise" for few milliseconds instead of the key sound, and only when it fades I have a little bit of the note that I was supposed to play.

I have the same "white noise" problem is I use Rose Garden.

I have tried to change the sample rate and the frames/period settings, and also the Timeout, in JACK, but the problem stays the same.


Thank you in advance for any help you can give.


Best,


Fabio

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