Design Article
H.264 "zero" latency video encoding and decoding for time-critical applications
Kishan Jainandunsing, PhD, W&W Communications
9/7/2007 4:00 AM EDT
Latency and zero latency defined
Simply put, video codec latency is defined here as the time lapse between the first pixel of video appearing in the source and the first pixel of decoded video appearing at the destination. Latency-sensitive video applications require that the time lapse between source and decoded video is extremely small. How small depends on the application, but as a guideline, keeping latency down to sub 10ms is a good idea. For convenience we will call such low latency "zero" latency. This is in contrast with the orders of magnitude higher latency found in non latency-sensitive applications.
Figure 1: Latency between source and decoded video
Latency sensitive video codec applications
In video conferencing and video telephony, noticeable delay makes a conversation impossible, unless a "walky-talky" like protocol is strictly followed. This makes the conversation unnatural and cumbersome. In these applications sub 33ms latency for the video codec is required.
Figure 2: Implications of latency in video conferencing
Next: Home networks, other latency sensitive video codec applications, unexpected benefits
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