User's Manual
Table Of Contents
- 1: Introduction
- 1.1 Documentation notes
- 1.2 Product introduction
- 1.3 General product handling and operation
- 1.3.1 Powering on/off and sleep mode
- 1.3.2 Attaching, detaching, and handling modules
- 1.3.3 Attaching the Wi-Fi antenna
- 1.3.4 Attaching the strap
- 1.3.5 About the touchscreen display
- 1.3.6 Selecting the active interface
- 1.3.7 Starting a function or test
- 1.3.8 Stopping a test
- 1.3.9 Saving results
- 1.3.10 Interpreting results
- 1.4 Maintenance
- 1.5 Technical support
- 2: Wi-Fi Testing Menu
- 3: 10/100 Testing Menu
- 4: System Menu
- 5: IP and Video Testing
- 5.1 IP Network Setup
- 5.2 Connection Information
- 5.3 Ping
- 5.4 Traceroute
- 5.5 Web Browser
- 5.6 IP Video testing
- 6: Specifications
Base Unit User Guide Issue 1 Tech-X Flex™
5-22 5: IP and Video Testing
Intro
Wi-Fi
10/100
System
IP/Video
Specs
received the referenced frame before the B-frame can be decoded, making the frame order different
from the actual display order. Therefore, B-frames can cause a delay in the decoding process,
because the decoder must buffer the input while reordering the frames for display. Of the three, the
loss of a B-frame generally causes the least impact to picture quality.
At the data level, a frame is divided into slices which represent horizontal sections of the frame. Each
slice is further divided into macroblocks which represent rectangular sections of the slice. This
organizational structure is the reason that digital video exhibits “rectangular” errors when data becomes
corrupted, rather than the general fuzz and/or static caused by a poor analog signal. For example:
• If macroblock data is missing or corrupted, the video typically shows rectangles of missing picture on
the screen, amidst an otherwise clear picture. Likewise, if a whole slice can’t be rendered, a larger
rectangular portion is missing.
• If whole frame data is missing or corrupted, the video may freeze on certain pictures altogether,
rendering the last known frame while waiting for new frame data.
GOP types
For any video stream, a set of frames is called a group of pictures or GOP, with the specific sequence
known as the GOP structure. A common GOP structure would include one I-frame, followed by two B-
frames, then followed by one P-frame, and so on, represented as “IBBPBBP…" The following figure
represents a simplified diagram of frame reference and interpolation, using a typical GOP structure:
Figure 5-6 Compressed video stream frames
Audio compression
I frames P frames B frames