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DynaGuard 200 Series: Why does not DG200 record fully 15 seconds of video files if we set up pre-alarm to 15 seconds? |
[2005/11/22] (4354) |
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A: As you may know, a MPEG4's video have three components: I frame, B frame, P frame. The I frame is a complete video data. The other two are only the difference value from the previous video data. The codec will use MPEG4's algorithm to calculate the current video data according to these three components. So when the program start to playback, it must locate a complete video data (aka. an I frame) to start the playback. Or you'll only see a meaningless video data. |
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