3D Material and Video Processing and Encoding (technical)

[flexy]

I have some questions in regards whether 3D material (field seqential) needs different approaches in regards to video encoding.

I got some information i nregards of this subject off peter wimmers site, where he explains how to discard fields from the material, then extract the left/right movies and save them to HD. He also has a program to re-mux those two videos again, but it only supports WMV.

My (very technical) questions...like:

Encoding material using XVID or Divx....wouldnt those codecs assume that subsequent frames "belong together"...and therefore encode wrong, or introducte artifacts?
Given...that in interlaces/field sequential material each frame belongs to either LEFT or RIGHT...the encoder has to see them as seperate and NOT belonging together.

If i encode movies in "encode interlace"..eg. in XVID..does it mean that the encoding then takes care of this problem?

I did various encodes and tests...i did extract the real left right parts of movies and did video processing on the two movies seperate, and then i watched the resutls with stereoplayer.
I also encoded using Xvid ("encode interlaced") as well as "non interlaced"

All my observations tell me that it doesnt matter at all, if i take field sequential material and encode it "as is"...it looks the same as if i would extract left/right first and threat both parts as seperate.

Also..i have not found a way, after i discarded fields and created two seperate movies (L + R) to actually multiplex them again into field sequential. I tried 10000 tools...but i have no idea how to mux two videos again into one avi. (Exception, as mention P.Wimmers WMVMux, but i couldnt read/mux anything with it since it seems to be very picky with WMV format)

I also dont see the use in extracting left/right since all my experiments showed it doesnt matter, interlaced, side by side field unfolded on screen, two seperate movies.....end esult is always the same.

Maybe someone knows more in regards to video encoding/processing usign 3D material.

[android78]

Sorry I can't give full technical details (someone else may be able to), but I believe that the 'encode interlace' option will encode the first field, then the second field seperate. In usual situations (where the fields have been taken from a movie film) the fields will actually have been taken from the same frame on the movie film (filmed at 25 FPS) so it won't matter if you encode as interlaced or not. video film on the other hand often, the even field will actually be slightly after the odd field (for NTSC it will be 1/60th of a second after) so if you don't encode it as interlaced then you will have blurring of fields, which could be an issue on fast-moving scenes, but no problem with a static image.
Providing my assumption is correct, for field sequential S3D encoding, you would have to encode as interlaced. To test this, I'd suggest getting film strip where every second line is black and first is white and test the encoding options (try creating a .bmp image and include that in the original film). See if one encoding option retains the black and white better then the other without having them both turn grey.
I'd love to know from a video encoding expert though!

[flexy]

yes, good idea!!

[flexy]

so..i did some tests..making a video black-white-black-white

When i encode in xvid, interlaced or not...also in WMV....the information is always retained. One frame black..next white.

So..my concerns about merging two adjacent frames wrongly dont apply.

This is actually weird...since one assumes that using any encoding....it would result in a gray video...

[android78]

I'm not sure if you just typed the wrong thing, or if you didn't understand me.
For alternate fields you need to have every second line to be Black

Code: Select all

BBBBBBBBBB
WWWWWWWWWW
BBBBBBBBBB
WWWWWWWWWW
BBBBBBBBBB
WWWWWWWWWW
BBBBBBBBBB
WWWWWWWWWW

My assumption is that encoding with encode interlace will actually encode as:

Code: Select all

Field 1
BBBBBBBBBB
BBBBBBBBBB
BBBBBBBBBB
BBBBBBBBBB

Field 2
WWWWWWWWWW
WWWWWWWWWW
WWWWWWWWWW
WWWWWWWWWW

Rather then just as a single frame (as per the top example.)
Maybe this is what you did though?

[flexy]

you are right, must have had a brain-fart.

I mixed up "interlaced" with "alternating frames" for a while.