Channel change time

The actual time it takes to switch between two multicast channels (sometimes called zap time) depends on a large number of factors. Some important ones are:

• The switches/routers introduces a delay after the IGMP join message, until the multicast stream is let through. In some cases this can be several hundred milliseconds.
• The portal pages usually draws new images and objects, and execute JavaScript code. If designed poorly, this can cause delays.
• You always need to buffer an amount of data before starting playing the new stream, to robustly handle jitter and variations in bit rate.
• Depending on the stream characteristics, you need to parse more or less data to extract vital information to start the stream (e.g. PAT/PMT tables).

Generally, you need longer time (more buffers) to ensure higher robustness against jitter and variations in bit rate. This implies that with less buffering, you get faster zap times, but may experience audio/video problems if the buffer runs empty.

Streamer buffer size

It is possible to modify the buffer used when playing video (or audio) streams. The default values used will ensure that the buffer never runs empty (or full) when watching typical MPEG streams.

On some streams where the characteristics is known beforehand it's possible to reduce the zap time by modifying the buffer size used. See the section on Media Player Parameters for more details.