Program that specifies interlacing?

[jdachik]

Hi guys, I'm wondering if you know of a freeware program that will tell you the interlace order (upper or lower field first) of an MPEG-2 file. Vegas seems to show it in the properties, but I am not positive that it is always accurate, so I'm wondering if there is another program I can use to verify it. Thanks for your help.

[zoobie]

try gspot

[jdachik]

Thanks. I have tried it, and in addtition to TFF (top field first) and BFF (Bottom field first) it lists PPF (picture per field) under "interlacing." This is separate from Progressive and it says PPF means "each field is encoded as its own MPEG picture." This is not something I've run into before. A file that is giving me interlacing trouble (received from someone else) is listed with this type of interlacing, Vegas listed it as "lower field first." The person who sent it to me said that they had exported it as "Upper field first" in cleaner (Media Cleaner, I presume). Does this PPF setting sound familiar to any of you guys?

[SLK001]

The problem with programs that tell you which field comes first is that they only look at the flags encoded in the video - and these are not always correct. The better way to find out the field order is to assume one of the orders, separate the fields, then single step through a high motion clip and see if there is a "progressive" progression of the fields. If you see a "jump back (in time)" while stepping through, then the field order specified is wrong. Assume the other order, then repeat the above as a check.

As for the PPF listing, I'm assuming that it is refering to a "ZIG-ZAG" scan (used for progressive sources) and an "ALTERNATE" scan (used for interlaced sources).

[PuzZLeR]

You can try DGIndex (free and no installation necessary). Load the video then press F5 to preview and check the status window after a few seconds of it scanning the video. (You can stop it any time.)

However, after reading this thread I'm doubting any utility is accurate though.

[edDV]

If the guy that sent this is pro or semipro, "cleaner " probably means Discreet Cleaner (now Autodesk). Ask him how it was encoded.

[manono]

each field is encoded as its own MPEG picture.

Pic_structure is field rather than frame. You can open it in Bitrate Viewer and it'll also tell you that information.

It encoded individual fields, rather than the fields being part of frames. And, as SLK001 said, to find the field order, assume one, separate the fields, advance a frame at a time, and if it plays smoothly, you guessed right, if it plays jerkily, you guessed wrong. In AviSynth, you'd do it like this:

AssumeTFF()
SeparateFields()

Open the script in VDub(Mod) and advance. If it's smooth, it's TFF, and if it is jerky (kind of 2 steps forward and one step back), then it's really BFF.