High Compression and Illusion
Another way to think about video compression is that it is an optical illusion. We think of it as compressing data, but beyond the most basic compression algorithms, the trick of compression is to drop information that will not commonly be noticed by the observer. In other words, on playback, a highly compressed image fools the eye into seeing more information than is present. In addition, with the h.264 codec used in the GO-HD camera, the illusion part of compression becomes apparent. What happens is that when you play back a video clip, it looks like true 1280x720 HD as if it had been recorded in 30 frame per second progressive video. However, if you slow that playback down and start to look at the individual frames, a lot of the information and detail that you expect to be there really isn’t – it is just a trick of the compression method. The actual information isn’t stored.
Look at these two images. The one on the left was shot with a still camera, the Panasonic Lumix, which goes for about the same price as the GO-HD. The Lumix is sold as a still camera, but also shoots DV video clips to SD memory.
The one on the right was shot with the GO-HD. Okay. The color is off on the GO-HD compared with the Lumix. One thing that is interesting is that the GO-HD shows the flowers transitioning from red on the left to a sort of pink color on the right. However, the still camera shot the image pretty much as I saw it, with all red flowers. There is color detail in the GO-HD image that did not exist in the real scene!
Look also at the tree trunk. See how detailed and textured the tree is in the Lumix image? However, in the GO-HD image the trunk looks sort of flat and lacking in detail. The compression has dropped out detail that would not normally be missed if I didn’t have a way to record what I was looking at on site. These images were taken minutes apart using a tripod. I shot the GO-HD image from the tripod and then replaced it with the Panasonic Lumix and took another picture.
