Iomega Buz
Rendering Loss Example


This image illustrates the loss problem with VideoWave's rendering, and probably the software MJPEG encoder in general. The image below is a half-and-half frame made from the Before and After AVI files. The lower left is a single frame from the AVI capture file.

Here's what I did to make the image: I captured a few seconds of the video test pattern from a signal generator, using VideoWave's capture tool. The settings were 720x480, 100k/frame, composite input. I saved this AVI file as the "Before" example. I used VideoWave to copy one frame from this AVI to the clipboard, and saved that image as a BMP file. This represents the video directly from the Buz capture file, and you can see it in the lower left corner.

Then I dropped the AVI file into the VideoWave timeline, and generated an "identical" output file, using the same settings. Ideally, we would expect the output to be byte-for-byte identical, since no changes were made and the parameters are the same. But as we know, VideoWave decodes and encodes every frame of the file anyway. (Premiere, for example, would simply copy the existing file contents.)

When VideoWave regenerates the video, there is significant loss. In this example, you can clearly see:

You might not always notice this in your own work, because the entire output video is affected. Motion and lack of source detail could hide the added blur as well. However, if you look closely, most people can sortof tell that the output video is never as good a quality as the source AVI files.

You can also download a full uncompressed BMP file, if you're concerned about JPEG artifacts confusing the issue. The BMP file has the exact pixels from the AVI frames.

The source of the video test pattern (and crude text overlay) is a Tektronix Pathfinder NTSC pattern generator, connected to the composite Video In on the Buz. It's very clean and accurate.

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Copyright ©1998 Steve Haehnichen