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Advanced Metrics

Streamcheck makes available to you all of information collected on your streams, down to the check-by-check data.

    • The time profile
    • Check Details pop-up window
    • Scanner and server information
    • Packet stats
    • Framerate
    • URLs and sources
    • DNS information
    • Traceroute


The time profile


The time profile shows the number of seconds spent connecting, buffering, rebuffering and playing during a specific check. This profile says that 22 seconds were spent connecting, 5 buffering, 31 playing and 3 rebuffering. The number in parentheses is the number of rebuffer events. Here, it says that all 3 seconds of rebuffering occurred in one event. This is important to know because of the rebuffering penalty applied when calculating StreamQ™.
(For more information on StreamQ click here.)



The diagram below shows the relationship between these quantities in a graphical manner, for an example 60 second check with two rebuffering events.




Check Details pop-up window


The Check Details pop-up window is available through the web interface by clicking on one of the colored circles in the Check Details section of results page. Doing this will bring up a window with a series of Check Details lists - one for each check that was done in the hour.

An example Check Details List is shown below and referenced in the remaining sections on this page.




Scanner and server information


Every check involves a conversation between a Streamcheck Scanner and a streaming server using one of several streaming protocols (UDP, TCP or HTTP). Information about the Scanner is given on the "Location" line. Information on the server is given on the "Server Type" line.

In the example above a Toronto Scanner, connecting through UUNet, spoke via UDP to a version 8 RealServer, running on Linux.


Packet Stats


Since all streaming protocols are built on top of TCP/IP, a packet-based system, one can always look at a streaming transaction from a packet perspective. Information about lost packets can help diagnose problematic streams.


Framerate


For streams that contain a video component, the frame rate can provide an indication of the playback quality. For audio only streams (and video streams of certain formats) this number is not reported.

A number of caveats must be observed when discussing frame rate for streaming files. See the question "Why isn't frame rate a top level metric?" in the Streamcheck FAQ.


URLs and sources


A single streaming experience can involve multiple files and URLs depending on the format and delivery type.

In Streamcheck terminology, the "Original URL" is the URL supplied provided by you to the system (and by the system to the Scanner). This URL should be the same as the URL your user would provide to their streaming player (either directly or through a web link).

The Original URL may be a metafile (usually .ram, .asx, .wax, .wav or .smi), in which case, it will also be listed in the "Metafile URL" field. The Original URL may instead link to metafile, in which case that new URL will be listed in the "Metafile URL" field. This is the case shown above. Finally, the Original URL may be a final Source URL or link directly to a Source URL, in which case, the "Metafile URL" field will say "unknown".

A Source URL is one that contains actual audio or video data. (For live feeds, this URL refers to a "mount point" on a streaming server.) If a metafile is used, there can be more than one source URL involved. Which Source URLs actually get streamed by the Scanner depends on how they are organized within the metafile. The Check Details List only includes URLs that are played by the Scanner.

In the case above, a brief ad (ad2341643.rm) was followed by the main content (midday.rm).

The chain of URLs can be summarized graphically as below.



DNS information


In order to play a stream, the first thing a streaming player must do, and hence the first thing a Streamcheck Scanner must do, is to turn a text-based URL to a numerical IP address. This is look-up process is called "DNS resolving" and can add unexpected delay to the connect time of a stream.

In most cases, DNS resolving takes under 1 second. In the example above, it took 0.5 seconds. If there is an error during this process, it will be reported in the "DNS Status" field.


Traceroute


Traceroutes provide a snapshot of Internet conditions during the checking process. Each time a check is performed, the Scanner performs a traceroute to the host specified in the original URL.

Often traceroutes provide a "sanity check" when diagnosing streaming problems. For instance, if a check shows excessive buffering times or low connectivity a traceroute showing low hop times can eliminate Internet congestion as the root cause of the problem.


 
 
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