Try this. You need to specify $sce
as a dependency.
.controller('DetailsCtrl', ['$scope', '$routeParams', '$http', '$sce',
function($scope, $routeParams, $http, $sce) {
$scope.loading = true;
$scope.url = $sce.trustAsResourceUrl('//www.youtube.com/embed/4wOoLLDXbDY');
$http.get('projects/' + $routeParams.projectId + '.json').success(function(data) {
$scope.project = data;
$scope.loading = false;
});
}]);