TimeDX Help.


Digital Video Test

    DMDX has the ability to use the componants that MicroSoft used to name Active Movie which they now call DirectMedia that play .MPG, .AVI, and Quicktime files (possibly others as well, see Codecs below). DirectMedia consists of two componants, DirectAnimation and DirectShow of which DMDX will be using DirectShow. Currently (I think) the DirectMedia stuff needs to be installed in addition to DirectX unless you are using 98 that has it installed already. This test checks that DirectShow (quartz.dll) is indeed installed and functioning and in addition it checks whether DMDX is going to be able to keep track of the retrace as a file is playing.
    As with graphics in general in DMDX, a 16 bpp display mode will work much better that a 256 color mode for displaying digital video as the palette is not updated.

    This test functions by playing a given Digital Video file, beit .MPG or whatever. After the file has played out various statistics are displayed. As the file is being played clicking the mouse will stop play. The test has several different ways of being run.
    The Audio Only checkbox is to test the streaming audio abilities, no video is displayed. When Audio Only is checked the frame numbers are considered to be millisecond values.
    It can either be made to stretch the video by checking the Strech check box and filling in the width and height edit boxes or it will center the video and display it at it's original size.
    DirectSound can be initialized to see how it interacts with DirectShow by checking the DirectSound check box.
    The vertical retrace thread can be activated to determine how it interacts with DirectShow by checking the Track Retrace check box.
    A portion of the digital video can be played back by checking the Play Region check box and by specifiying the starting and ending frame numbers.

    Displayed data after the run include:
    Run Transistion time: how many milliseconds DirectShow took to produce the first sample from the file.
    Samples displayed: how many samples were actually displayed -- this can be different from the number of frames in the Digital Video file.
    av. ms per sample: After the first sample the average number of milliseconds between successive samples displayed (not the time between samples in the file).
    Multiply timedout retraces and Certain Errors are the results of the retrace thread keeping track of the retrace, see the Vertical Retrace Sync Thread explanation for their meaning.
   
    Enabling Track Retrace on slower systems (a Pentium 133 for example) you can definitely see a performance hit, faster systems where the frame rate is higher than the usual 24 or 30 fps in the Digital Video file don't notice it.

    During playing of a Digital Video file several keys can be used to control and display information.
    P either pauses or plays the stream.
    T displays the current timecode, pausing the stream if it wasn't paused already. When DMDX plays portions of a Digital Video these timecodes are used as the indexes.
    < or > cues the paused stream forward or backward, if it's not paused cueing will pause it. The stream is cued by the current time quantum, by default two frames.
    1 2 3 4 5 6 7 8 9 set the cueing time quantum in number of frames.
    0 toggles whether the cueing quantum is multiplied by ten or not.
   
    Codecs

    The file types that DMDX and TimeDX can handle are determined by what DirectShow can handle which is in turn determined by that codecs have been installed on the machine. A codec (short for coder/decoder) can handle different types of compression, the default '98 codec handles .AVI, .MPG, and Quicktime video formats (possibly others as well) and the .WAV audio format. While I have yet to find a codec that decodes the very attractive .mp3 audio format files (the Fraunhauffer codec supposedly had this ability but it isn't available anymore due to copyright infringements) at sometime in the past the development box must have had a codec installed on it as it has the curious ability to play .au files (typically 2:1 compression) where the test machine cannot. Might've been the Intel Indeo 5 codec, however I can't find that codec anymore so I can't say for certain.

    Which brings us to the all important question, how can you tell what file formats are supported on your machine? Good question. Under the Control Panel / Multimedia / Devices option you can see what Video and Audio codecs have been installed but getting a file type out of that information seems impossible, so other than by trial and error I suspect you are SOL. To use the time honored try it and see approach simply try and play the file with TimeDX's / Advanced / Digital Video test, if it's an audio file check the Audio Only check box. If your machine can't handle the file format TimeDX will report and error like this:

Failed to OpenFile
VFW_E_CANNOT_CONNECT (80040217)
No combination of intermediate filters could be found to make the connection.

    A filter is DirectShow's name for the objects that the codecs provide to do the decoding.
   
   


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