Binding to viewmodel from inside a datatemplate

I have multiple videos displayed they are bound with a videocollection in Mainviewmodel. Everything works fine untill I try to bind the enter command to Mainviewmodel. I Don't know the syntax for this. As it stands the binding is set to Video and not Mainviewmodel.

Errormessage:

'StartVideoCommand' property not found on 'object' ''Video'   

Xaml:

<Window.Resources>
  <local:MainViewModel x:Key="MainViewModel"/>
</Window.Resources>
  <Grid DataContext="{StaticResource MainViewModel}">
    <ListBox ItemsSource="{Binding Videos}">
      <ListBox.ItemTemplate>
        <DataTemplate>
          <Grid>
            <Grid.InputBindings>

!!!           <KeyBinding Key="Enter" Command="{Binding StartVideo}" /> !Bound to Video not to Mainviewmodel grrr  

            </Grid.InputBindings>
             ... layout stuff
              <TextBlock Text="{Binding Title}" Grid.Column="0" Grid.Row="0" Foreground="White"/>
              <TextBlock Text="{Binding Date}" Grid.Column="0" Grid.Row="1" Foreground="White" HorizontalAlignment="Left"/>
              <TextBlock Text="{Binding Length}" Grid.Column="1" Grid.Row="1" Foreground="White" HorizontalAlignment="Right"/>
             ... closing tags

Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type Window}}, Path=DataContext.StartVideo}"