EXFO EXpert IPTV Test Tools (FTB-200v2) - Manual (Page 52)

52
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.
A.1.2.1 Impact of Coding Bitrate on Video Quality
For a typical MPEG‐2 encoded video stream with standard resolution 720x486, GOP
sequence IBBPBBPBBPBBPBB, at 30 frames per second, the mean square error (MSE) due to
bitrate can be approximated by:
MSE
br
= 0.00001 + 1.5 / (B + B 2 / 30000).
Where B is the bitrate in kilobits per second. The corresponding peak signal‐to‐noise ratio