Troubleshooting Performance
In an ideal QGE 100 system, the source displayed on the viewing device should be virtually indistinguishable from the original source. However, under certain circumstances, you may notice some reduction in performance. This section describes the problems you may encounter and provides suggestions for minimizing or avoiding them.
Performance Criteria
The performance criteria include the following:
•Image Refresh Rate — how often the display content is updated. Ideally, this should match or be as close as possible to the refresh rate of the original source.
As the refresh rate decreases, you notice a loss of smooth motion on the screen. For example, a moving mouse cursor may appear to move smoothly at a fast refresh rate but jerkily at slower rates.
The QGE 100 features a variable source refresh and update rate (frame rate). To ensure smooth motion, it use the highest possible refresh rate. However, during periods of intense screen activity, the refresh rate may be temporarily reduced to compensate for the higher volume of data.
•Image Latency — how long a change in the original source takes to be seen in the viewed source. Ideally, this should be instantaneous (in real time).
In practice, there is always be some delay introduced by the electronics and software that process the data between the original source and the viewing station; however, this is usually small enough to be ignored. As the latency increases, a greater time lag becomes noticeable between events happening on the original source and the same events being seen on the viewed source.
•Image Quality — the sharpness and color of the viewed source in comparison to the original. When the source is viewed at the same resolution as the original, there should be no discernible differences.
If any scaling is applied to the source (so that it is displayed smaller or larger than the original) there is always some small loss of sharpness. This is an inherent side effect of image scaling.
Things that Impact Performance Criteria
Data stream bottlenecks
The QGE 100 streams only data relating to changes in the source display. Therefore, a source containing a lot of movement (such as an MPEG movie) creates more data than a source with little or no movement (such as a spreadsheet file). Changes in latency or refresh rate can arise when a bottleneck occurs at some point in the data path which restricts the flow of data. Potential bottlenecks include:
•Data Encoding — Data from the source capture process is encoded into a QGE 100 data stream and sent to the network. Under normal circumstances, the QGE is capable of encoding most sources without any difficulty. However, if you are using a high resolution source containing a lot of movement, the encoder may generate more data than can be transmitted between frame captures.
In this situation the encoder can temporarily reduce the refresh rate, allowing more time for the data to be sent (see “Optimizing the Encoder Parameters” on page 55).
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