Interlaced/progressive flag mix-up

[Mr Chris]

Somebody's sent me a bunch of DVD images (ISOs) on an HDD, but having burnt a few to disc, it's clear he's authored them incorrectly. Simply put, everything plays back as progressive, when the footage is clearly interlaced. What's my easiest course of action to correct the ISOs?

Many thanks.

[DB83]

Buy the dvds

(read the rules)

[Mr Chris]

These are home-made DVDs - not commercial ones. (Hence the error in authoring, obviously.)

[DB83]

I stand corrected.

What I would suggest is that you load a vob into avidemux, select copy for video and audio and mpeg as the format. Then mark a short sample of the offending footage and upload that sample.

Better for respondents to work with a sample that simply guess on what is going on.

[jagabo]

Most software players can be forced to deinterlace during playback. Otherwise you'll probably have to reencode and reauthor. Some problems (blurred chroma, DCT ringing) will remain though.

[DB83]

And reencode/reauthor will result in loss of quality.

[Mr Chris]

Most software players can be forced to deinterlace during playback. Otherwise you'll probably have to reencode and reauthor.

Please excuse my ignorance, but surely it's just a flag that needs changing somewhere, isn't it? Something's telling my DVD player that the picture is progressive when it's not - isn't there a setting somewhere in the IFOs that I can switch to "Interlaced"?

(And, almost as pertinently, can I do it without completely unpacking all the ISOs? I suspect the answer to this is no, but I live in hope!)

[newpball]

It may be bad deinterlaced progressive and in that case it is pretty much fubar

[jagabo]

I'm not an expert on DVD structure but it doesn't seem likely to me that the IFO files will contain interlace/progressive information. MPEG 2 video can switch between interlaced, progressive, and pulldown flags at every GOP, at least. A program would have to go through all the VOB files and switch all those flags. This would also cause color decoding problems (in addition to those that have been caused by incorrectly encoding interlaced frames as progressive) since the decoder will treat the progressive chroma as if it's interlaced.

[manono]

Please excuse my ignorance, but surely it's just a flag that needs changing somewhere, isn't it? Something's telling my DVD player that the picture is progressive when it's not - isn't there a setting somewhere in the IFOs that I can switch to "Interlaced"?

It's definitely not in the IFOs but in the video stream itself. As jagabo mentioned, the flags can change on a dime. Also, if interlaced it should have been encoded interlaced to begin with. You can demux the DVD (PGCDemux), take the resulting M2V and have it marked as interlaced (ReStream), remux (Muxman), put the 'fixed' one back into the original DVD (PGCEdit), and your player should then deinterlace it (unless there are other problems, such as the improper resizing of interlaced material). But there will be problems which you may or may not notice and which may or may not bother you.

As DB83 suggested, a short sample (10 seconds or so, one with movement) will tell us more as well.