Cannot link gstreamer plugins to gst-launch in snap

snapcraft
1

Hi,

I am trying to use a gstreamer plugin called “v4l2src” to live stream webcam images as a snap

I have managed to build gstreamer in snapcraft and launch gst-launch. However, gst-launch is unable to link any of the plugins.

  1. I have tried copying everything to the prime directory and setting the environment variables using the environment in the apps
parts:
 gstreamer:
    plugin: autotools
    source: https://gstreamer.freedesktop.org/src/gstreamer/gstreamer-1.5.2.tar.xz
    configflags:
      - --prefix=/usr
      - --with-install-plugins-helper=/path/to/installer
    prime:
      - usr
    build-attributes: [no-system-libraries]

 gst-plugins-base:
    after:
      - gstreamer
    plugin: autotools
    source: https://gstreamer.freedesktop.org/src/gst-plugins-base/gst-plugins-base-1.5.2.tar.xz
    configflags:
      - --prefix=/usr
    build-attributes: [no-system-libraries]

 gst-plugins-good:
    after:
      - gstreamer
      - gst-plugins-base
    plugin: autotools
    source: http://gstreamer.freedesktop.org/src/gst-plugins-good/gst-plugins-good-1.5.2.tar.xz
    configflags:
     - --prefix=/usr
    prime:
      - usr
    build-attributes: [no-system-libraries]


apps:
  gst-launch:
    environment:
      GST_PLUGIN_PATH: usr/lib/gstreamer-1.0
      GST_PLUGIN_SYSTEM_PATH: usr/lib/gstreamer-1.0
      GST_PLUGIN_SCANNER: usr/libexec/gstreamer-1.0/gst-plugin-scanner
      # LD_LIBRARY_PATH: usr/lib
      PATH: $SNAP/usr/local/bin:$PATH
    command: usr/bin/gst-launch-1.0

However, the plugins are not seen by gst-launch.

$ gstreamer.gst-launch v4l2src device=/dev/video0 ! video/x-h264,width=1920,height=1080,framerate=24/1 ! h264parse ! rtph264pay ! udpsink host=xxx.xxx.xxx.xxx port=5000
ERROR: pipeline could not be constructed: no element "v4l2src".

I tried creating a app that echos the environment variables and have checked that the environment variables are indeed there.

I was wondering if I am misunderstanding the accessibility of the prime directory on runtime. Should the libraries be copied to the $SNAP_DATA rather than the prime directory?

How can I link the plugins to the gst-launch?

Thank you in advance

2

Your paths in the GST environment variables are not anchored. Therefore they are relative to whatever the current directory happens to be when the user launches the app. e.g. if I am in $HOME and I run your application then it will look for the gstreamer assets in $HOME/usr/lib/gstreamer-1.0. You simply need to prefix with $SNAP/ to ensure the paths are correctly pointing into your snap’s root filesystem:

apps:
  gst-launch:
    environment:
      GST_PLUGIN_SCANNER: $SNAP/usr/libexec/gstreamer-1.0/gst-plugin-scanner
      ... # etc...
2 Likes
3

@lucyllewy

Thanks, I the snap currently works setting the path as you have suggested