Hello Tom
The first thing you should do is to determine how much bandwidth your voice and video will require. For a remote site with only four IP phones, 30Mbps is way too much. If you’re using the G711 codec, each conversation, along with headers, will consume close to 90 Kbps according to Cisco. For four conversations, that’s a maximum of 360Kbps. Now an HD video transmission shouldn’t take more than about 4 or 5Mbps, while lower quality video will take much less than that. That should give you an idea of what kind of bandwidth you should be reserved on the link.
As for the application of QoS on the IP phones, you must identify the traffic you want to prioritize, and then to apply the QoS mechanisms to do this.
For the first, you can take a look at these lessons which talk about the classification of traffic, ways in which you can mark this traffic for special treatment, and methods of doing this at both Layer 2 and Layer 3, depending upon your topology.
The classification and marking will be applied on the switch, so that voice traffic can be identified. The next thing you have to do is apply QoS mechanisms at the appropriate location on the network in order to provide the desired special treatment of the voice packets. Specifically, you want to apply this to the VPN connection. You can do this by either applying shaping or policing. You can find out more about these, including their differences at the following lessons:
Because these lessons deal with QoS on IOS devices, you can find out more about how QoS can be applied to Cisco ASA devices as well, so that the QoS can be implemented on your VPN:
I hope this has been helpful!
Laz