Is there a way to change a progessive MPEG2 file to interlaced?

[redeemer-dk]

I've just finished encoding a lot of MPEG2 clips. These clips were originally interlaced, but i forgot to uncheck the "Progressive" checkbox in DoCCE4U. AFAIK the difference betweeen a progressive and an interlaced stream is some flags in the stream that can either be set to progressive or interlaced. Is there a program that can change these flags in the stream, so it becomes interlaced instead of progressive?

Thanks

-Rune Svendsen

[Kika]

The Tool restream can change this Flags.

[Doom9]

you may be able to change that flag but what good would it do? I'm not sure on the decoding side, but on the encoding side it's much more than a flag: in interlaced encoding all the even and the odd lines are grouped and then compression is performed. This increases effectiveness if you are actually dealing with interlaced content, but decreases effectiveness if your content is progressive.

If your source was actually interlaced (meaning you see combing effects in the video), then you have interest to encode interlaced or deinterlace and encode progressively. If your source just had the interlaced flag set but has no combing, it was a progressive source encoded interlaced, and you did the right thing encoding it progressively. Encoding progressive material in interlaced mode isn't so much of a problem, it's just a little less effective - as for the other way round it's no tragedy either, but I'm not sure if changing that flag wouldn't actually change the decoding process in an undesirable way. If you do try it, please let us know about the results (despite the bottom line being you shouldn't bother changing those flags).

[redeemer-dk]

Thanks to both.

Doom9: You're right. I'm reencoding them right now and i'll make some comparisons later. The differences i can think of is that with progressive material i set the scanning order to zigzag and with interlaced material i set it to alternate (which is the recommended setting), that should make a difference. And also the motion search compensation is done very differently when dealing with an interlaced source compared to a progressive source.