Can't open PsychPortAudio in mode 8 ('master mode')

Hi fellow PTB-users,

I am trying to open an audio port in mode 8, which is the master mode so that I can start using 'OpenSlave'. I tried the following:

>> InitializePsychSound;
>> hAudioMaster = PsychPortAudio( 'Open', [], 8, 0, 44100, 2 );


This gives the following error:


PTB-INFO: Using specially modified PortAudio engine, based on offical version: PortAudio V19-devel
PTB-ERROR: Desired audio parameters for device -1 unsupported by audio device. PortAudio reports this error: Invalid device
PTB-ERROR: This could be, e.g., due to an unsupported combination of audio sample rate, audio channel allocation, or audio sample format.
PTB-ERROR: On Linux you may be able to use ALSA audio converter plugins to make this work.
INTERNAL PSYCHTOOLBOX ERROR
    error:                PsychError_system
    general description:  Error reported by a system call
    specific description: Failed to open PortAudio audio device due to unsupported combination of audio parameters.
    module name:          PsychPortAudio
    subfunction call:     Open
    file name:            Common/PsychPortAudio/PsychPortAudio.c
    function name:        PSYCHPORTAUDIOOpen
    line number:          2420


I tried changing the deviceID (the [] in the above function call), and different values for sampling frequency and number of channels. Opening an audio port in modes other than 8 (1, 2, etc.) does work.


I see the suggestion "may be able to use ALSA audio converter plugins to make this work", but I don't know what is meant by this.


Has anyone experienced the same problem? Thanks in advance for your help!


Best,

Mark


My system: Ubuntu 16.04 LTS, MATLAB R2017b, PsychToolboxVersion: "3.0.14 - Flavor:  - Corresponds to SVN Revision"