[pitivi] Disable vaapi plugin unless explicitely enabled

[Thibault Saunier <tsaunier src gnome org>]

commit d416e94e25d9e1be254018ea67e06a03fa9a8b05
Author: Thibault Saunier <tsaunier gnome org>
Date:   Mon Aug 14 21:51:16 2017 -0300

    Disable vaapi plugin unless explicitely enabled
    
    And install gstreamer-vaapi in the sandbox
    
    Reviewed-by: Alex Băluț <<alexandru balut gmail com>>
    Differential Revision: https://phabricator.freedesktop.org/D1839

 build/flatpak/pitivi.template.json |   12 ++++++++++++
 docs/Install_with_flatpak.md       |    8 ++++++++
 pitivi/check.py                    |   15 +++++++++++++++
 3 files changed, 35 insertions(+), 0 deletions(-)
---
diff --git a/build/flatpak/pitivi.template.json b/build/flatpak/pitivi.template.json
index 60e9b5e..d7b3c0f 100644
--- a/build/flatpak/pitivi.template.json
+++ b/build/flatpak/pitivi.template.json
@@ -404,6 +404,18 @@
             ]
         },
         {
+            "name": "gstreamer-vaapi",
+            "buildsystem": "meson",
+            "builddir": true,
+            "config-opts": ["-Ddisable_gtkdoc=true", "--libdir=lib"],
+            "sources": [
+                {
+                    "type": "git",
+                    "url": "git://anongit.freedesktop.org/gstreamer/gstreamer-vaapi"
+                }
+            ]
+        },
+        {
             "name": "gst-editing-services",
             "buildsystem": "meson",
             "builddir": true,
diff --git a/docs/Install_with_flatpak.md b/docs/Install_with_flatpak.md
index 7539557..7c2a045 100644
--- a/docs/Install_with_flatpak.md
+++ b/docs/Install_with_flatpak.md
@@ -79,3 +79,11 @@ If a new version is fetched, it will be made current.
 If your software manager doesn't allow this yet, run the command below:
 
 ` $ flatpak --user uninstall org.pitivi.Pitivi stable`
+
+## Install GStreamer vaapi support
+
+In the sandbox gstreamer-vaapi is installed but it requires the
+org.freedesktop.Platform.VAAPI.Intel extension to be installed.
+
+As the support is experimental, you need to set PITIVI_UNSTABLE_FEATURES
+to enable them: `flatpak run --env=PITIVI_UNSTABLE_FEATURES=vaapi org.pitivi.Pitivi`.
diff --git a/pitivi/check.py b/pitivi/check.py
index 4e5a00e..e5c9b72 100644
--- a/pitivi/check.py
+++ b/pitivi/check.py
@@ -238,6 +238,19 @@ def _check_videosink():
     return videosink_factory
 
 
+def _check_vaapi():
+    from gi.repository import Gst
+    if "vaapi" in os.environ.get("PITIVI_UNSTABLE_FEATURES", ""):
+        print("Vaapi decoders enabled.")
+        return
+
+    for feature in Gst.Registry.get().get_feature_list_by_plugin("vaapi"):
+        if isinstance(feature, Gst.ElementFactory):
+            klass = feature.get_klass()
+            if "Decoder" in klass and "Video" in klass:
+                feature.set_rank(Gst.Rank.MARGINAL)
+
+
 def _check_gst_python():
     from gi.repository import Gst
     try:
@@ -295,6 +308,8 @@ def check_requirements():
                 "Make sure you have a gtksink available."))
         return False
 
+    _check_vaapi()
+
     return True