Incorrect field order

[genak]

I accidentally encoded an interlaced MPEG with the wrong field order - is there any way I can change this without having to re-encode from the source file again?

Thanks

[Abond]

ReStream. No need to reencode. Field order is simply a flag.

[AngusMacGyver]

Try using pulldown.exe.
There are many switches and almong them there is one to change field order.

[byteguy]

ReStream. No need to reencode. Field order is simply a flag.

That's not true.

Yes, there is a flag for field order and you can change it with ReStream. But... it will make the file look A LOT WORSE. I e-mailed the author of ReStream when I had this problem, he says his tool is just to fix the flag when the encoding program sets it wrong or forgets to set it but actually changing the encoded order doesn't happen.

Because ProShow uses a different field order than my capture card, I have to mix files with different field orders all the time. The ONLY way is to flip the field order on one and re-encode. Sorry.

Here are my quick and dirty notes of what I do:

HOW I SWAPPED THE FIELD ORDER ON PROSHOW FILES

Used Restream to confirm which MPG2 files had which encoding

Found that all of them had top-field-first except for the slideshow from ProShow Gold

Installed the Huffyuv codec

Installed VirtualDub MP2.

Installed the updated Reverse Field Order Filter

Loaded my slideshow into VirtualDUB. Added the video filter and turned off the audio (didn't need it). Set the video compression to Huffyuv. Saved the AVI. This was still a big file: 4.5GB for 6 minutes. I could probably set options to make it smaller, but I wasn't going to keep it for long.

Loaded the AVI into an empty EditStudio project.

Changed the build options to upper field and saved as MPEG DVD.

New MPG2 file loaded great with others and I built the final project with upper field set.

[Abond]

Then the answer is:
Yes, there is a way, but byteguy has problems with it (me - never). The decission you have to make what to use.
BTW can you elaborate a bit, why it should be worse? I think the encoder encodes FRAMES, but not FIELDS. I am aware that Procoder has field encode mode, but from what I have read, the output is not compliant with existed media.

[byteguy]

BTW can you elaborate a bit, why it should be worse?.

I should point out that this is a problem with INTERLACED files only.

I can't find the cool link to the detail that I read before so here it is from memory...

Say you have a top-field first file.. the frames are encoded

A C E G
B D F H

and are displayed A - B - C - D - E - F - G - H

flip the flag but don't change the encoding and you display B - A - D - C - F - E - H - G and you get a God-awful "jitter" effect

Trust me, I tried to put a top-field first interlaced MP2 from ProShow with a bottom-field first interlaced MP2 from EditStudio and got jitter on the ProShow portion. Then I used ReStream to flip the flag on that input file and the result was some kind of worse double-jitter there. Once I ran it through VirtualDub and used its field flip function and then combined it with the other file everything was perfect.

On a non-interlaced file, it won't matter since the A and B are the same.

[byteguy]

Found the "cool link"

Here is everything you ever wanted to know about interlacing, field order, and general image construction.

http://neuron2.net/LVG/interlacing.html

[Abond]

All this info I have read already. I know what interlacing means and why the field order is very important with interlaced video. What I never ever seen is this double-jitter you describe there. I have made several encodes with not correct field order, and can see this "normal" jitter in the moving objects, but after correction the field order with ReStream everything was perfect and smooth. So I really can not understand the situation when after correction of the field order with restream it make it even worse - as I said in my case it was OK.

[lordsmurf]

ReStream. No need to reencode. Field order is simply a flag.

That's not true.

Yes it is.

his tool is just to fix the flag when the encoding program sets it wrong

Exactly. Just like the original poster has done, and is asking how to fix.

I have to mix files with different field orders all the time. The ONLY way is to flip the field order on one and re-encode. Sorry.

That's not necessarily true either. DVB and DSS formats constantly send MPEG video over satellite that has multiple field orders in the same stream. But I wouldn't suggest this sort of mess to work with.

[byteguy]

ReStream. No need to reencode. Field order is simply a flag.

That's not true.

Yes it is.

So, you are saying that there is NO difference between two MPEG2 files where one is encoded top-field first and the other is encoded bottom field first EXCEPT for the flag?

his tool is just to fix the flag when the encoding program sets it wrong

Exactly. Just like the original poster has done, and is asking how to fix.

The original poster said he had encoded it wrong, not that he had encoded it correctly but the flag was set wrong. You are right, we should have asked "is the field order the way you want it but the flag wrong or are both the flag and field order not the way you wanted?" The answer is different depending on that question.

[genak]

Thanks for your help

"is the field order the way you want it but the flag wrong or are both the flag and field order not the way you wanted?"

I'm not quite sure what you're asking... as far as I was aware, the field order is just a flag which tells the TV in which order to display the fields.

I encoded the file with TMPGEnc, with the field order set to "Bottom Field First" instead of "Top Field First", like so:

[byteguy]

Ok, your file is actually encoded bottom field first and the flag is set correctly. I still stand by my statement that changing the flag with ReStream will not cause it to magically become a top-field first stream.

Have you tried putting this on a DVD? Is it still clear? If so, then don't worry about it. DVD players will interpret the flag on the fly. They will even take multiple movies on the same disc with different settings and deal with them.

It is possible, if all your sources were top-field that you could ReStream this and get a good file. It's worth a shot and will only take a second.