Video Encoding

[storm5510]

I have a question that I am unable to find by searching on the web. Perhaps someone here can answer.

I have an ATI TV Wonder Pro capture/playback card in my computer. If I want to capture, there are three formatting options. Upper field first, lower field first, and progressive source.

I understand the first two. Can anyone tell me what progressive source is?

[koala]

Full details here and here.

Playback on analog devices (television set)
A television set is not the same as a computer monitor. A tv has exactly 525 scanlines (NTSC) on the complete tube, with a resolution of about 300/500x480. The amount of horizontal resolution depends on both the age and size of the tv set, with most of the 21-36 inch sizes carrying about 400 lines, whereas smaller sets with less resolution and larger ones with higher resolutions. Although a tv set can playback progressive source, it will not look as good as interlace source. A tv was made to playback interlaced analog source.

Playback on digital devices (computer monitor)
A computer monitor has nothing in common with a television set. It's refresh rate, resolutions and color-depth can be altered at will. A computer monitor is progressive rather than interlaced. While monitor can playback interlaced footage (often using DVD player software like PowerDVD or WinDVD), it will not look as good as playback on an analog device because varying de-interlace playback filters must be used. The computer is a progressive interface and does best with progressive playback.

To illustrate the meaning of progressive scan, let's take a look at that old analog TV in your living room. It most likely uses the interlace method to draw onscreen images. That is, the electron gun at the back of the TV tube first fires off the odd lines of the onscreen image, then during a second pass, it shoots out the even-numbered lines. This all occurs within 1/30 of a second, but what you wind up seeing is an acceptable picture that has some occasional flicker or artifacts.

Almost all HDTVs can draw progressive-scan pictures. Progressive scan works in the same manner as your computer monitor. It writes one full frame of video from left to right across the screen every 1/60 of a second. Since the entire image is drawn at one time --as opposed to an interlaced image where the even lines are drawn first, followed by the odd lines-- a progressively scanned video image looks more stable than an interlaced one. Progressive scan also introduces fewer motion artifacts, such as jagged diagonal lines and movement in fine detail, into the picture.

[storm5510]

Interesting. Thank you for the quick reply.

I'll toss in a clarification on my software. I was incorrect about the modes ATI uses. It can encode progressive source, de-interlace, and encode interlaced.

I post process using VideoStudio 10. It seems to have the ability to detect what the source is. It identifies progressive source and de-interlaced as being "frame based". Usually, it shows encode interlaced as upper field first.

I captured a short video a few weeks ago using the capture feature in VS10. That one ended up being lower field first. I was unable to salvage the video. I couldn't process it into anything else and not have it jerk wildly when played back on a TV. It's aspect ratio was also incorrect. It appeared as wide screen letterbox. Everything looked mashed, so that tells me half the lines were missing.