Why "Interlaced Enccode" ?

[Slavko_1]

I'm very sorry for my bad english. My question is - why XviD encoder "interlaced encode" option have ? I know what interlace is and i know, deinterlace video material before encode is the better way.Why should I encode interlaced material like "interlaced encode".None software player can't play this properly like interlaced scaned mateial.Someone players suggests "deinterlace" during playbak but I know It is bad idea. Better way is deinterlace video before encoding and encode it like progressive(better efficiency compression).Thanks for any answers.

[Manao]

Two reasons :
* On a TV ( or any interlaced display ), the motion in an interlaced video will look much smoother. So for some content ( sports, mostly ), it's better to keep the video interlaced.
* On a progressive display ( i.e, on a computer ), you can, during playback, "bob" the video ( that is, instead of doing 25i -> 25p, you do 25i -> 50p ), and the motion will also be smoother.

Since 25i is easier to encode that 50p, bobbing before encoding would degrade the quality.

[Slavko_1]

Thanks. I know about advantage field scaned materials over progresive (info about scene "looks like" is refresh 25 per second but info about move in scene is refresh 50 / s). Is any XviD standalone player properly plays field scaned material on TV for example ? Probably not. Typical TV-outs PC graphic cards can't do it too. When I want to play XviD movie on progresive display, my opinion is better way to bob it (or use better methods to recreate progressive frames) before and encode like 50 fps progressive material.Do you know about software player properly bobs (or interpolate maybe) video for example 640x480 and plays it like 50 fps ? Maybe exists emulator of interlace scanning for progressive display like PC monitor ?

[R3Z]

Two reasons :
* On a TV ( or any interlaced display ), the motion in an interlaced video will look much smoother. So for some content ( sports, mostly ), it's better to keep the video interlaced.
* On a progressive display ( i.e, on a computer ), you can, during playback, "bob" the video ( that is, instead of doing 25i -> 25p, you do 25i -> 50p ), and the motion will also be smoother.

Since 25i is easier to encode that 50p, bobbing before encoding would degrade the quality.

The motion in interlaced footage is only captured in half vertical resolution, so i dont really understand why progressive video captured at the same framerate would not look as smooth :confused:

[Slavko_1]

Look please on vertical lines in video (doors or windows edges) when camera slowly moves.Than you will see the difference. Probably human eye better wants "refresh" than detailes .

[Wilbert]

The motion in interlaced footage is only captured in half vertical resolution, so i dont really understand why progressive video captured at the same framerate would not look as smooth
25i means 50 fields (thus 50 different time instants). 25p means 25 frames (thus 25 different time instants). So 25i and 25p are *not* the same rate, and that's why the latter is smoother.

[Blue_MiSfit]

Exactly. Interlacing is all about improved temporal resolution, at the sacrifice of spatial resolution.

If you have interlaced content, try to keep it interlaced if at all possible... Deinterlacing is always very lossy :)

~MiSfit

[Manao]

Interlacing is all about improved temporal resolution, at the sacrifice of spatial resolution.No. If it was that, they would have done 50p at half the resolution instead of choosing the mathematical nightmare that interlacing is.

Interlacing provides the full spatial resolution when the video doesn't move, and the full temporal resolution when it moves.

[Blue_MiSfit]

Good point! I always assume the worst when it comes to interlacing :)

~MiSfit