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Testing document download performance

The Flash Player attempts to meet the frame rate you set; the actual frame rate during playback can vary on different computers. If a document that is downloading reaches a particular frame before the frame's required data has downloaded, the document pauses until the data arrives.

To view downloading performance graphically, you can use the Bandwidth Profiler, which shows how much data is sent for each frame according to the modem speed you specify. The Bandwidth Profiler is divided into two panes. The left pane shows information about the document, the download settings, the state, and streams, if any are included. The right pane shows information about individual frames in the document.

In simulating the downloading speed, Flash uses estimates of typical Internet performance, not the exact modem speed. For example, if you choose to simulate a modem speed of 28.8 Kbps, Flash sets the actual rate to 2.3 Kbps to reflect typical Internet performance. The profiler also compensates for the added compression support for SWF files, which reduces the file size and improves streaming performance.

When external SWF files, GIF and XML files, and variables are streamed into a player by using ActionScript calls such as loadMovie and getUrl, the data flows at the rate set for streaming. The stream rate for the main SWF file is reduced based on the reduction of bandwidth caused by the additional data requests. It's helpful to test your document at each speed you intend to support, and on each computer you intend to support. This helps you ensure that the document doesn't overburden the slowest connection and computer it is designed for.

You can also generate a report of frames that are slowing playback, and then optimize or eliminate some of the content in those frames. See Optimizing Flash documents.

To change the settings for the SWF file created using the Test Movie and Test Scene commands, use File > Publish Settings. See Publishing Flash documents.

To test download performance:

  1. Do one of the following:
    • Select Control > Test Scene or Control > Test Movie.

      If you test a scene or document, Flash publishes the current selection as a SWF file using the settings in the Publish Settings dialog box. (See Publishing Flash documents.) The SWF file opens in a new window and begins playing immediately.

    • Select File > Open, and select a SWF file.
  2. Select View > Download Settings, and select a download speed to determine the streaming rate that Flash simulates: 14.4 Kbps, 28.8 Kbps, 56 Kbps, DSL, T1 or a User Setting. To enter your your own User Setting, select Customize.
  3. When viewing the SWF file, select View > Bandwidth Profiler to display a graph of the downloading performance.

    The left side of the profiler displays information about the document, its settings, its state, and streams, if any are included in the document.

    The right section of the profiler shows the Timeline header and graph. In the graph, each bar represents an individual frame of the document. The size of the bar corresponds to that frame's size in bytes. The red line beneath the Timeline header indicates whether a given frame streams in real time with the current modem speed set in the Control menu. If a bar extends above the red line, the document must wait for that frame to load.

  4. Select View > Simulate Download to turn streaming off or on.

    If you turn streaming off, the document starts over without simulating a web connection.

  5. Click a bar on the graph to display settings for the corresponding frame in the left window and stop the document.
  6. If necessary, adjust the view of the graph:
    • Select View > Streaming Graph to show which frames cause pauses.

      This default view displays alternating light and dark gray blocks representing each frame. The side of each block indicates its relative byte size. The first frame stores a symbol's contents, so it is often larger than other frames.

    • Select View > Frame by Frame Graph to display the size of each frame.

      This view helps you see which frames contribute to streaming delays. If any frame block extends above the red line in the graph, the Flash Player halts playback until the entire frame downloads.

  7. Close the test window to return to the normal authoring environment.

Once you've set up a test environment incorporating the Bandwidth Profiler, you can open any SWF file directly in test mode. The file opens in a Flash Player window, using the Bandwidth Profiler and other selected viewing options.

For more information on debugging your documents, see Writing and Debugging Scripts.

To generate a report listing the amount of data in the final Flash Player file:

  1. Select File > Publish Settings and click the Flash tab.
  2. Select Generate Size Report.
  3. Click Publish.

    Flash generates a text file with the extension .txt. (If the document file is myMovie.fla, the text file is myMovie Report.txt.) The report lists the size of each frame, shape, text, sound, video and ActionScript script by frame.

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