Add VAAPI caps for transcoding

src/docker.js

@@ -325,6 +325,12 @@ function createSubcontainer(app, name, cmd, options, callback) {
         if (capabilities.includes('mlock')) containerOptions.HostConfig.CapAdd.push('IPC_LOCK'); // mlock prevents swapping
         if (!capabilities.includes('ping')) containerOptions.HostConfig.CapDrop.push('NET_RAW'); // NET_RAW is included by default by Docker
 
+        if (capabilities.includes('vaapi')) {
+            containerOptions.HostConfig.Devices = [
+                { PathOnHost: '/dev/dri', PathInContainer: '/dev/dri', CgroupPermissions: 'rwm' }
+            ];
+        }
+
         containerOptions = _.extend(containerOptions, options);
 
         gConnection.createContainer(containerOptions, function (error, container) {