Packet Delay Variation (PDV)

Question

I am currently implementing video streaming application where the goal is to utilize as much as possible gigabit ethernet bandwidth

• Application protocol is built over tcp/ip
• Network library is using asynchronous iocp mechanism
• Only streaming over LAN is needed
• No need for packets to go through routers

This simplifies many things. Nevertheless I am experiencing problems with packet delay variation.

It means that a video frame which should arrive for example every 20 ms (1280 x 720p 50Hz video signal) sometimes arrives delayed by tens of milliseconds. More:

• Average frame rate is kept
• Maximum video frame delay is dependent on network utilization
• The more data on LAN the higher maximum video frame delay

For example when bandwidth usage is 800mbps, PDV is sbout 45 - 50 ms.

To my questions:

• What are practical boundaries in lowering that value?
• Do you know about measurement report available on internet dealing with this?

I want know if there is some subtle error in my application (perhaps excessive locking) or there is no way to make numbers better with current technology.

Answer 1

For video streaming, I would recommend using UDP instead of TCP, as it has less overhead and packet confirmation is usually not needed, as the retransmited data would already be obsolete.