EXFO EXpert IPTV Test Tools (FTB-1 / 2 Pro) - Manual (Page 50)

50
Error mitigation algorithms are being increasingly applied to help to compensate for packet
loss [11][12]. Methods include:
Forward Error Correction (FEC) - redundancy is applied to the data stream to allow some
proportion of lost or errored packets to be replaced.
Interleaving - in which the video stream is split into alternate frames and each encoded
separately.
Macro-block error concealment - spatially corresponding macro-blocks are copied from the
previous frame.
These approaches can help considerably with tolerance to packet loss.
A.1.1.3 Playout Buffer Configuration
It is assumed that both videoconferencing and streaming video systems provide a playout
buffer; however, the configuration of these is quite different. It is highly desirable to
determine whether an application is streaming or interactive, since the playout buffer
configuration is typically very different for these two applications.
Following are examples for the playout buffer settings:
Videoconferencing - nominal 100ms (0.1 seconds), adaptive
Streaming Video - nominal 3,000ms (3 seconds), fixed
A.1.2 Encoding/Decoding Impairments
While transmission impairments such as packet loss are a common source of video quality
degradation, quality can also be affected by the encoding/decoding process itself; i.e., some
distortion can be introduced by the bitrate and codec used.