Field order change

[mits]

Season greetings and Happy New Year to all ,
My question is :
Is there a way to change the field order of an mpeg2 file without reencoding it ?

[DrP]

You can flip the field order flag in the video using project-x available at doom9.org's download section. Might do the job unless you really need to alter the field order in the video and not just tell the decoder how it is.

[Brian Ellis]

Theoretically, it should be possible to devise a software to do it but I don't know of one. It would require setting a single bit in the picture coding extension structure (assuming you are just swapping top and bottom first and not changing i to p). However, this extension must follow each picture sequence header, so it would have to be reset thousands of times in a practical video (this is why MPEG-2 will permit mixing top and bottom field first sequences, even if it is not clever). It would probably take just as long as re-encoding.

Why do you want to do it?

[mits]

Brian,
I was in a hurry and i encoded two clips with the wrong filed order and as a result it displays a "trembling" video on the tv. The avi files have been deleted.
Dr P,
i'll give project-x a try

Thanks