Interlaced DV AVI with no combing

[Alwyn]

I would be grateful if the experts could advise what's going on with the attached DV AVI. I captured it back in 2006 from my ADVC-100 (those were the days!) and IIRC I didn't do anything to it after capture. Mediainfo is showing it is Interlaced BFF but it shows no jaggies and steps through the bob doubler filter in VDub as though it is Progressive.

Is this, in fact, a progressive file and therefore MediaInfo is incorrect?

[Sharc]

Is this, in fact, a progressive file and therefore MediaInfo is incorrect?

It's progressive video, 25 frames per second, just encoded and flagged as interlaced, and MediaInfo reports it accordingly.
The even and odd fields are however taken from the same instant in time. You can process it as progressive.

[Alwyn]

Thanks Sharc.

[DB83]

Just a little curious about this clip.

Now my ADVC transfers say 'Canopus DV' or nothing (just DV) - these were done straight to the PC via WinDV.


Yours states 'Sony DV' which begs the question, if you can recall, the method/software you used. Maybe some version of Vegas which could have 'altered' the source.

[Alwyn]

DB83, that is a good question and as I said, I don't recall doing anything with it after capture, with the exception of possibly trimming it with Scenalyzer.

I have checked a DV file I captured with the ADVC-100 just last year and it's codec is also DVSD (Sony); that was definitely untouched post-capture.

Yet another I have from 2006 is CDVC (Canopus).

The mere fact that it is Progressive means that I must have done something to it but I was a rank newby then, compared to what I know now. I vaguely remember dabbling with various DV codecs; I don't know how "the system" picks a particular DV codec for capture if you have more than one installed. I may have even captured it with VDub into Progressive if that's possible. I also remember having issues with DV Type 1 and 2 for Movie Edit Pro and using DVDate to fix that; maybe it flipped the codec.

I'm just thankful that they didn't turn out too badly, all things considered.

[jagabo]

The mere fact that it is Progressive means that I must have done something to it

Not necessarily. Film broadcast as PAL video is typically done by speeding the film from 24p to 25p and transmitting one field at a time (ie interlaced) at 50 fields per second. So pairs of fields come from the same film frame. It you capture with the same field order as the broadcast you restore the original film frames -- every frame of your cap will look progressive. If you capture with the opposite field order all you frames will show comb artifacts when there is motion because every video frame contains a field from a different film frame.

4 film frames: 1 2 3 4
broadcast BFF: 1b 1t 2b 2t 3b 3t 4b 4t (a sequence of fields)
captured BFF:  1b+1t 2b+2t 3b+3t 4b+4t (appears progressive, like the film source)
captured TFF:     1t+2b 2t+3b 3t+4b 4t+5b (appears interlaced)

The TFF can be restored to progressive frames by recombining fields from the same film frame.

interlaced frames:   1t+2b 2t+3b 3t+4b 4t+5b
separate fields:     1t 2b 2t 3b 3t 4b 4t 5b
discard first field:    1b 1t 2b 2t 3b 3t 4b 4t 5b 5t
recombine fields:       1b+1t 2b+2t 3b+3t 4b+4t 5b+5t

This is not true for live video sources where every field comes from a different point in time -- 50 fields per second for analog PAL video. With video sources no pairing of fields will give comb-free frames when there is motion.

[Alwyn]

Of course, I think you (or somebody) have said that before, Jagabo. Always learning. I should start writing this stuff down.