AngularJS filter for nested objects

I have an array of objects with arrays of objects in it:

var content = [
  { 
    name: 'Foo',
    sub: [{ name: 'Bar' }, { name: 'Foobar' }] 
  },
  ...
]

and a template:

<input ng-model="search" />

<div ng-repeat="item in content | filter:search>
   {{item.name}}
   <div ng-repeat="key in item">
      {{key.name}}
   </div>
</div>

Now, I use the filter filter to search for string matches, but it applies only to the first ng-repeat directive. How could I include the second directive into the search filter? Thanks in advance.