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In Reply to: Progressive and interlaced posted by Some Guy on November 26, 2003 at 06:16:25:
"DVDs can be encoded with either a progressive or interlaced signal. "Then which is true?
1. If we decode the disc into interlaced signal, we are throwing away half of the information on the disc.
2. When we decode the disc into progressive scan signal, we are creating additional information (not originally on the disc) by the player's processor's interpolation calculation.
Does it depend on the disc? Then is it written on the disc cover which is the case?
Follow Ups:
> > DVDs can be encoded with either a progressive or interlaced signal.> Then which is true
> 1. If we decode the disc into interlaced signal, we are throwing
> away half of the information on the disc.If you're using a regular TV (non-progressive) then your DVD player is just converting the progressive signal into an interlaced signal... about 30 full frames per second into 60 fields (or half-frames split every other line) per second.
> 2. When we decode the disc into progressive scan signal, we are
> creating additional information (not originally on the disc) by
> the player's processor's interpolation calculation.It's not really creating additional information, but rather combining the fields together into one frame and presenting it that way. You can generally see the effects of this in motion shots... they appear more choppy.
The key to understanding the difference between interlaced and progressive is the understanding the difference between fields and frames. One frame is made up of two fields. The term "interlaced" comes from the fact that each field is presented one after the other, first the odd rows, then the even rows, which is then referred to as one frame. Progressive simply pops up the full frame (or both the odd and even fields at the same time... sort of.) Progressive is the same principle as film, although film only moves at 24 fps against NTSC videos rate of 29.97 fps and PAL at 25 fps.
The actuality is that we only refer to frames per second with NTSC as a reference... frames don't really exist. It's all fields. There is no pause between each set of fields, so it's odd/even/odd/even and so forth... Feel free to read up on it some more.
http://graphics.lcs.mit.edu/~tbuehler/video/ntsc.html
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