Still having some issues occasionally. Every now and again PTQ stops producing piano sounds and all I get is noise. Restarting it gets it working again. I'm going to upgrade/change the whole OS soon (and ditch bloody KDE) so I won't bother trying to fix it now.

Edit: Actually, restarting PTQ does not always fix the problem. Right now all that works is increasing the buffer size to around 1024 samples which results in unacceptable latency...

Edit #2 (30 Dec 2015): Changing the sampling rate from 48kHz to 44.1kHz got things working again with buffer size of 128 (or even 64). And oddly enough, if I change the sampling rate back to 48kHz, it still works fine. Weird.

Edit #3 (4 Jan 2015) After more of the same issues (ones mentioned in this post) I added myself to the audio group and rebooted. Everything works fine (for some days now). I use JACK sometimes to route MIDI between other software (e.g., MuseScore) and Pianoteq. All good.

Could be a Dell BIOS issue or a bad temperature reporting issue.  Perhaps the laptop is reporting that it's getting too hot and so it scales down when in reality it's not.

It's strange that you had issues: I'm running fine with a less powerful i3-3217U with Lubuntu 15.04.

I don't know the reason but the CPU speed switching seemed to have caused the glitches. I will try it with slower fixed speed CPU setting and see how that goes.

I applied the recommended steps in Pianoteq readme.txt (including Jack). It was running fine at 48000 Hz / 128 buffer, but needed to set "performance" governor for more demanding tasks (or increasing buffer size).
Then I installed the low latency kernel, and it made a big difference: now I seldom need to change the default "powersave" governor (it seems to me that the reason is that this low latency kernel is much more reactive to speed change needs). I prefer the "powersave" governor since the notebook is quieter, neeeding less fan cooling.

acpi-cpufreq

Thanks, interesting, that Linux Mint 17.2 has not switched over to scaling_driver intel_pstate.

could you please show, which scaling_driver your system is running?

acpi-cpufreq

could you please show, which scaling_driver your system is running?

with ...

cat /sys/devices/system/cpu/cpu0/cpufreq/scaling_driver

for ((i=0; i<$(cpufreq-info | grep analyzing | wc -l); i++)); do sudo cpufreq-set -g performance -c $i; done

------------------------

Long version:

How I got Pianoteq 5 flying on Linux (after some initial woes)

I had a bit of trouble getting Pianoteq Std working without issues on my Linux Mint 17.2 Dell laptop. It's a fairly capable machine, i5-3337U 1.8GHz, 8GB RAM - should be plenty to run PTQ.

Yet I kept getting crackling/popping sounds every now and again (even without CPU overload), and latency was not all that reliable or great (not near what PTQ claimed) and polyphony was pathetic (<10, at most 20) on "Pessimistic".

Things I tried (but did not solve the problems)
- Low latency Linux kernel (this is usually a good idea)
- JACK audio set up for realtime audio (this actually made things a bit worse; but it wasn't JACK's fault, see below)
- "sudo renice"-ing the 'Pianoteq 5' process to -20 (if you don't know what that means, don't worry; if you're curious, look up the "renice" command in Linux)

What worked in the end:
- Disable CPU throttling and set all CPUs/cores to run at their maximum speed

You can accomplish this with the cpufreq-set command (part of the cpufrequtils package, installed by default on most Linux systems). But first to see your settings and hardware info run cpufreq-info (in a terminal window). The only info you really need is how many CPUs (cores) the OS thinks you have. You can read the full output of cpufreq-info or if it's too much info, do something like this:

ptquser@mycompter:/home/ptquser/Pianoteq Standard 5.42/Pianoteq 5/amd64 > cpufreq-info | grep analyzing
analyzing CPU 0:
analyzing CPU 1:
analyzing CPU 2:
analyzing CPU 3:

So here we have four CPUs/cores and they are numbered 0 to 3. We want to configure all of these for performance, which will disable on-the-fly CPU speed changes and will always run them at their max rated speed (without overclocking). This is accomplished with cpufreq-set:

ptquser@mycompter:/home/ptquser/Pianoteq Standard 5.42/Pianoteq 5/amd64 > sudo cpufreq-set -g performance -c 0
[sudo] password for ptquser: 
sudo cpufreq-set -g performance -c 1
sudo cpufreq-set -g performance -c 2
sudo cpufreq-set -g performance -c 3

This fixed all the issues. I torture tested it and polyphony "Pessimistic" goes over 100, latency is non-existent, there are no glitches in the sound output and the CPU never overloads. My final PTQ configuration is:

- Audio device type: ALSA (not using JACK, no need for now but may use it in future)
- Output: PulseAudio Sound Server
- Sample rate: 48000 Hz
- Audio buffer size: 128 samples (2.7 ms)
- Multicore rendering ON
- CPU Overload detection ON
- Internal sample rate: 48000 Hz
- Max polyphony: Auto (Pessimistic)

Cheers.