Video applications sit at layer 7 of the OSI model. They can demand high bandwidth due to the requirement to send frames as well as audio.
Real time video applications (such as Telepresence) require minimal delay and should be prioritised in the QoS configuration.
One-way videos (such as You-Tube) are not as sensitive to delay and jitter. They can be buffered by the client then replayed to produce a high quality output.
Video traffic is generally 'bursty', groups of images sent together, whilst a pause may result in few packets being sent together.
As a result traffic flow need to be managed and planned for. Consider the following requirements for Video then plan your QoS deployment across the switch infrastructure accordingly.
Video requires High bandwidth, less than 150ms delay, low jitter, <1% packet loss, high availability, potential for PoE (such as Video Conference equipment).