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Video Capture (FAQ)

1. My LiveVideo doesn't work (sometimes it shows one frame only), but there are no error messages in the message window. What is happenning?
The root of this is the dirty little hack we do to get video in the background. Basically, we assume that at some point, a single texture (to contain the video) is being used, and find its OpenGL texture ID (DART's video only works with OpenGL, not Direct3D). Then, we shove the video into that texture as the application is running. If there are more than one texture loaded when we look for this texture id in videoSetupVideoToTexture, it might pick the wrong one. This could happen if you have content in the 3D world when this is called, or if some old textures aren't removed when you application is stopped. In these cases, arranging to have no content in the world when the background texture is checked for, or restarting Director (for the latter problem) will fix it.
Another possible reason relates to the graphics card:
  • On new computers with advanced graphics cards (like ATI Mobility Radeon 9700) we are experiencing problems updating the background polygon texture in live video. You will ikely see one frame or a few frames at the most. If you are rendering other objects besides the background polygon, you should get the live video just fine.
  • The graphics card will not refresh textures on OpenGL objects if it thinks nothing has changed. Generally this is good, but we are making this work by grabbing the texture object directly from the xtra.
  • A solution to this has been posted on the download page under October 13, 2004. Current users should get the zip file labeled (diff from previous) and unzip it to the DART directory on your machine. This should replace the file where some code was added. The changes are logged in the changes.log file added to each revised zip file.

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