In my tests, StreamQ gave the public radio station stream an A during peak work hours and an A+ at other times. I drilled down by date and time to pinpoint the location of the scanner, the original URL of the file or metafile requested, the server type, and the number of packets received and lost during playback. Information was available on the actual bit rate of delivery and buffering and rebuffering times. I could find the DNS resolution time and the results of a trace route to the network path used by the player and the server, including round-trip delay time in milliseconds. I could also review the error code the player received.
In most cases when a scanner couldn't connect with the server, the scanner reported RealPlayer Error code 800400C4 ("Server has reached its capacity"). When the StreamQ rating dropped from A+ to A, the trace-route data showed problematic network delays.
Sean Doherty is a technology editor based at our Syracuse University Real-World Labs®. Write to him at [email protected].
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Many variables affect the video quality as perceived by end users on the desktop. Most of these depend on the encoding and decoding process and the frame rate delivered to the user. The frame rate differs based on the codec used and the decoding process, and that will vary depending on whether the process is done in hardware or software and what video player is implemented on the desktop. All these variables can lead away from an objective metric of quality to a subjective determination of quality; they can even be misleading. For example, RealPlayer's decoder provides information on the frame rate delivered to the desktop. However, it polls the frame rate after it interpolates frames. This can result in a frame rate higher than the encoded rate. And when you start comparing frame rates, you quickly digress to a subjective preference for a codec that delivers fewer frames with high resolution and color depth or more frames with less resolution and color. It is important to note that Keynote's Streaming Perspective measures the frame rate of some streams and includes the metric in the stream details, but this is not included in its StreamQ metric.
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