Newbie questions about resolution, fps and interlacing

[nonoitall]

Okay, what I want to do is capture video from my satellite receiver (not digitally, but through a composite line). I want to preserve as much quality as possible and am wondering what resolution and fps I should be capturing at, and whether I should capture interlaced or progressive frames.

[edDV]

DBS MPeg2 resolution falls between 480x480 to 524x480 depending on the service. Composite output is NTSC 59.94 fields per second (interlaced).

DVD capture resolution can be 352x480 or 720x480. If playback to a TV is the goal, it is best to maintain interlace. Exception would be film sourced material that could be inverse telecined to 23.976 fps progressive if you want. This would save 20% disc space.

[nonoitall]

So if I capture it interlaced, I should capture at 59.94 fps, and at with 480 as a vertical resolution? Or would it be 29.97 fps? (The concept of interlacing always hurt my brain horribly.)

[jagabo]

Standard defintion NTSC video (everything you've ever seen on a normal TV) consists of 59.94 half pictures every second. Each half picture (called a field) consists of every other scanline of the picture. If one field contains all the even scanlines, the next will contain all the odd scanlines. The broadcast simply alternates between even and odd fields.

On a TV you always see one field at a time, never both. When computers capture those fields they pair the fields up into frames since they contain complimentary scanlines. You now have 29.97 frames per second. If nothing moved during the 1/59.94 seconds interval between the two fields the frame looks like a normal picture. But if anything moved you will see interlace comb artifacts. In essence, two different half pictures have been woven together into one picture.

Those interlace artifacts aren't a problem if you burn a DVD correctly. When the DVD player plays the video it will separate the fields and send one at a time to the TV, restoring the original 59.94 fields per second. What you see on the TV will be exactly the same as the original broadcast.

So capture at 720x480 or 352x480, 29.97 frames per second -- which is really 59.94 fields per second.

[pijetro]

Excellent explanation jagabo...

nonoitall wrote:

I want to preserve as much quality as possible and am wondering what resolution and fps I should be capturing at, and whether I should capture interlaced or progressive frames.

Do as jagabo has suggested...
As far as quality goes, you're already taking a hit by using the composite for capture..Of course, i've captured beautiful footage with composite in the past nonetheless...
Otherwise, the next step in your search for quality, is to find out if the footage is Telecined...
This is essentially Film footage, converted for NTSC..
What Inverse Telecine does, is take all of what jagabo explained, and returning back to Film framerate..

The quick and dirty way to know if the source was telecined to begin with:
Open up the .AVI in VirtualDub, go to a scene where the camera pans, and click forward keyframe by keyframe..
If the footage has three progressive steps, and two interlaced steps, it has been telecined..
Determine this, and continue on....

Good luck!!!

[nonoitall]

Okay, I think that covers it. Thanks a lot guys!