The Illusion of Detail
The image below is magnified 200% to show you what’s going on in the detail of the picture. Look at the flowers and at the leaves. Look at the edge of the white flowers. The codec has rendered them almost as cartoons. They are composed of solid areas of only two or three colors. Likewise, the tree trunk is really only constituted of, perhaps, three or four colors. In addition, look at the edge of the white flowers. See the square stair-stepping around the edges?
What’s going on here is that the blocky edges around the white flowers, when seen half the size and when the image is changing at 30 frames per second, makes the video appear to be sharper and to have more detail and more information than is really present. The jagged edges fool the eyes. The brain knows that the jagged edges are not natural, so it interprets them as an indicator of detail.
This is the illusion that the compression method provides, sort of laid out for you to see. The digital artifacts make the image look sharp on playback. However, when you go to make changes to the video – you can see that the detail really is not there.
Now – why should you care if the video you are looking at appears to have more detail than it actually does? The answer to that is rather tricky. If you can perform cuts-only edits on the native file, then the illusion will be maintained and there is little down-side so long as you stick to the format and compression it was shot in. But if you intend to do any kind of more sophisticated editing – even a dissolve from one shot to another – or if you intend to output the video into a higher quality codec – such as for a DVD – then the compression artifacts will likely be revealed and spoil the illusion – and the quality – of the result.
If you plan to do transitions, color correction, or other effects – high compression codecs like this one are not going to produce the best visual results.
Getting to an Editable Format
High compression has several consequences. It makes it extremely hard and perhaps impossible to get back the original frames that you think should be there if you are familiar with 720p 30fps video. When you look at the individual frames, the detail just is not there.
