Voice Over IP

EVALUATING CODERS

In evaluating the performance of codecs, several factors come into play. A summary of these factors is shown in this list:

• Frame size: Frame size represents the length of the voice traffic measured in time. It is also called frame delay. Frames are discrete parts of the speech, and each frame is updated based on the speech samples. The codecs covered in this chapter process a frame at a time. This traffic is placed in voice packets and sent to the receiver.

• Processing delay: This factor represents the delay incurred at the codec to run the voice and coding algorithm on one frame. It is often simply factored into the frame delay. Processing delay is also called algorithmic delay.

• Lookahead delay: Lookahead delay occurs when the ...