Saturday, January 31, 2015

The Difference between Interlaced and Progressive Video (Ⅰ)

There is no denying that the interlaced format is the earliest known form of video compression. As a matter of fact, it is developed in order to address early TV technology challenges and broadcast bandwidth constraints. However, interlaced video was not perfect enough to satisfy people’s various requirements. Therefore, the progressive video was developed as a newer technology which can help meet people’s requirements under specific conditions.

As for interlaced video, each field of a video image displays every other horizontal line of the complete image. For instance, in the first field of the interlaced video, the even-numbered lines will be displayed, and then the odd-numbered lines of the same image will be shown with the second field of the same interlaced video. If this even/odd sequence is repeated frequently enough, for example, 25 to 30 times per second, then the viewer will be able to see the complete moving image with the help of the persistence of human vision.

It is well known that the interlaced video allows more detailed images to be created than would otherwise be possible within a given amount bandwidth, which is its main benefit. As a matter of fact, a doubling of image resolution is also allowed in interlaced video. However, there are also some problems which cannot be ignored. In the first place, interlaced video comes with real-world downside. On the other hand, image softening will take place during fast-motion sequences. In addition, moiré or strobing artifacts are likely to occur in the process of showing striped shirts, plaid jackets, bricks in a building or similar types of objects.

In comparison with interlaced video, progressive video has greatly gotten rid of such problems and thus enjoy more popularity among people. It is possible that progressive video will play a more important role than interlaced video in the future.