Stuttering audio that hangs: QSoundEffect and QMediaPlayer

JHBR

Hi

For a long time now I've been struggling with getting an application to run smoothly on my RPi3. The issue is when playing audio. The application uses QMediaPlayer to stream mp3-files, while at the same time playing wav-files with QSoundEffect when certain buttons are pressed, events happen etc.

The QSoundEffect sounds stutters a lot, sometimes halting all audio playback (even the concurrently streaming mp3) until I trigger another QSoundEffect, after which the "queued" sounds all come "stumbling" at once and the mp3 resumes, albeit usually with a lot of stuttering.

If I try to run the application without pulseaudio running, I get the following error:

xcb_connection_has_error() returned true
PulseAudioService: pa_context_connect() failed
xcb_connection_has_error() returned true
PulseAudioService: pa_context_connect() failed
Assertion 'pthread_mutex_unlock(&m->mutex) == 0' failed at pulsecore/mutex-posix.c:110, function pa_mutex_unlock(). Aborting.

However, if I also don't use QSoundEffect, the application runs perfectly without pulseaudio. So I assume QSoundEffect is dependant on pulseaudio, while QMediaPlayer is not.

With pulsaudio running, even if I don't use QSoundEffect, the mp3 playback still has a tendency to stutter, especially when I toggle quickly to the next/previous track (I use QMediaPlaylist together with QMediaPlayer). Interestingly, however, without pulseaudio running, the mp3-streaming with QMediaPlayer is perfectly smooth, with less delay and no stuttering.

This is on a Raspberry Pi 3 with Qt 5.8 (both native build and cross-compiled on Ubuntu).
I initially tried it on Qt 5.7, experiencing the same issues, but I was hoping Qt 5.8, with its transfer from Gstreamer0.10 to Gstreamer1.0 as a backend, would perform better. Alas, the same issue remains.

The application audio works perfectly with Qt 5.7 on Windows 8.1 and with Qt 5.8 on Unbuntu 16.04.

Any help or tips would be greatly appreciated!

JHBR

If of any interest, this is the config.summary from cross-compiling Qt 5.8 for the RPi3:

Building on: linux-g++ (x86_64, CPU features: mmx sse sse2)
Building for: devices/linux-rpi3-g++ (arm, CPU features: neon)
Configuration: cross_compile compile_examples enable_new_dtags largefile neon precompile_header shared rpath accessibility release c++11 concurrent dbus mremap reduce_exports stl
Build options:
  Mode ................................... release
  Building shared libraries .............. yes
  Using C++ standard ..................... C++11
  Using gold linker ...................... no
  Using new DTAGS ........................ yes
  Using precompiled headers .............. yes
  Using LTCG ............................. no
  Target compiler supports:
    NEON ................................. yes
  Build parts ............................ libs
Qt modules and options:
  Qt Concurrent .......................... yes
  Qt D-Bus ............................... yes
  Qt D-Bus directly linked to libdbus .... yes
  Qt Gui ................................. yes
  Qt Network ............................. yes
  Qt Sql ................................. yes
  Qt Testlib ............................. yes
  Qt Widgets ............................. yes
  Qt Xml ................................. yes
Support enabled for:
  Accessibility .......................... yes
  Using pkg-config ....................... yes
  QML debugging .......................... yes
  udev ................................... yes
  Using system zlib ...................... yes
Qt Core:
  DoubleConversion ....................... yes
    Using system DoubleConversion ........ no
  GLib ................................... yes
  iconv .................................. yes
  ICU .................................... no
  Logging backends:
    journald ............................. no
    syslog ............................... no
    slog2 ................................ no
  Using system PCRE ...................... no
Qt Network:
  getaddrinfo() .......................... yes
  getifaddrs() ........................... yes
  IPv6 ifname ............................ yes
  libproxy ............................... no
  OpenSSL ................................ yes
    Qt directly linked to OpenSSL ........ no
  SCTP ................................... no
  Use system proxies ..................... yes
Qt Sql:
  DB2 (IBM) .............................. no
  InterBase .............................. no
  MySql .................................. no
  OCI (Oracle) ........................... no
  ODBC ................................... yes
  PostgreSQL ............................. yes
  SQLite2 ................................ yes
  SQLite ................................. yes
    Using system provided SQLite ......... no
  TDS (Sybase) ........................... yes
Qt Gui:
  FreeType ............................... yes
    Using system FreeType ................ yes
  HarfBuzz ............................... yes
    Using system HarfBuzz ................ no
  Fontconfig ............................. yes
  Image formats:
    GIF .................................. yes
    ICO .................................. yes
    JPEG ................................. yes
      Using system libjpeg ............... yes
    PNG .................................. yes
      Using system libpng ................ yes
  OpenGL:
    EGL .................................. yes
    Desktop OpenGL ....................... no
    OpenGL ES 2.0 ........................ yes
    OpenGL ES 3.0 ........................ no
    OpenGL ES 3.1 ........................ no
  Session Management ..................... yes
Features used by QPA backends:
  evdev .................................. yes
  libinput ............................... yes
  mtdev .................................. yes
  tslib .................................. yes
  xkbcommon-evdev ........................ yes
QPA backends:
  DirectFB ............................... no
  EGLFS .................................. yes
  EGLFS details:
    EGLFS i.Mx6 .......................... no
    EGLFS i.Mx6 Wayland .................. no
    EGLFS EGLDevice ...................... no
    EGLFS GBM ............................ yes
    EGLFS Mali ........................... no
    EGLFS Raspberry Pi ................... yes
    EGL on X11 ........................... no
  LinuxFB ................................ yes
  Mir client ............................. no
  X11:
    Using system provided XCB libraries .. yes
    EGL on X11 ........................... no
    Xinput2 .............................. yes
    XCB XKB .............................. yes
    XLib ................................. yes
    XCB render ........................... yes
    XCB GLX .............................. yes
    XCB Xlib ............................. yes
    Using system-provided xkbcommon ...... no
Qt Widgets:
  GTK+ ................................... no
  Styles ................................. Fusion Windows
Qt PrintSupport:
  CUPS ................................... yes
QtXmlPatterns:
  XML schema support ..................... yes
Qt QML:
  QML interpreter ........................ yes
  QML network support .................... yes
Qt Quick:
  Direct3D 12 ............................ no
  AnimatedImage item ..................... yes
  Canvas item ............................ yes
  Support for Quick Designer ............. yes
  Flipable item .......................... yes
  GridView item .......................... yes
  ListView item .......................... yes
  Path support ........................... yes
  PathView item .......................... yes
  Positioner items ....................... yes
  ShaderEffect item ...................... yes
  Sprite item ............................ yes
Qt Gamepad:
  SDL2 ................................... no
Qt 3D:
  System Assimp .......................... no
Qt Bluetooth:
  BlueZ .................................. no
  BlueZ Low Energy ....................... no
  Linux Crypto API ....................... no
Qt Sensors:
  sensorfw ............................... no
Qt Multimedia:
  ALSA ................................... yes
  GStreamer 1.0 .......................... yes
  GStreamer 0.10 ......................... no
  Video for Linux ........................ yes
  OpenAL ................................. no
  PulseAudio ............................. yes
  Resource Policy (libresourceqt5) ....... no
  DirectShow ............................. no
  Windows Media Foundation ............... no
Qt Location:
  Gypsy GPS Daemon ....................... no
  WinRT Geolocation API .................. no

Note: Also available for Linux: linux-clang linux-kcc linux-icc linux-cxx

Note: PKG_CONFIG_LIBDIR automatically set to /home/jhbr/raspi/sysroot/usr/lib/pkgconfig:/home/jhbr/raspi/sysroot/usr/share/pkgconfig:/home/jhbr/raspi/sysroot/usr/lib/arm-linux-gnueabihf/pkgconfig

Note: PKG_CONFIG_SYSROOT_DIR automatically set to /home/jhbr/raspi/sysroot

Note: Dropped compiler flags '-pthread' when detecting library 'glib'.

Note: Dropped compiler flags '-pthread' when detecting library 'gstreamer'.

Note: Dropped compiler flags '-pthread' when detecting library 'gstreamer_app'.

And among others, I have installed the following relevant dependencies on the RPi3:

DEPS+=" libasound2-dev"
DEPS+=" libpulse-dev"
DEPS+=" libavcodec-dev"
DEPS+=" libavformat-dev"
DEPS+=" libswscale-dev"
DEPS+=" gstreamer-tools"
DEPS+=" libgstreamer1.0-dev"
DEPS+=" libgstreamer-plugins-base1.0-dev"
DEPS+=" gstreamer1.0-omx"
DEPS+=" gstreamer1.0-plugins-good"
DEPS+=" gstreamer1.0-plugins-bad"
DEPS+=" gstreamer1.0-plugins-ugly"
DEPS+=" gstreamer1.0-libav"
DEPS+=" gstreamer1.0-clutter"
DEPS+=" gstreamer1.0-fluendo-mp3"
DEPS+=" gstreamer1.0-pulseaudio"

StoatPatronus

I realize that this topic is older (2 months at the time I'm writing this) but I stumbled across it when I was having a similar issue with QSound and QSoundEffect. My solution was to uninstall PulseAudio from my Pi, and install libasound2-dev. Then I rebuilt Qt with -no-pulseaudio -alsa configure options. My QSound and QSoundEffect programs work great now.

JHBR

Thank you, @StoatPatronus , that seemed to do the trick for me too!