Technical Committee on Human Factors - Guidelines for real-time communication services
Effects on the communication process
Turn-taking - there may be
- More turn taking with video communication than with audio
- More pauses and interruptions when video communication has a delay of 500 ms( compared with no delay)
- Less simultaneous speech with a smaller video image
Length of dialogue - there may be
- More words used with video communication than with audio
Facial speech - with lip shape information
- Listeners can tolerate 4-6 dB of additional noise for the same level of understanding
Lip reading
- < 12 fps is too low
- 20 fps gives good quality
- QCIF resolution is adequate
- 400 ms delay is adequate