Combing in pure-film material

[binba]

Hi everyone,

Glad to be back in AviSynth land - I always return to this wonderful tool when I've got challenging video to fix.
After 6 hours of tinkering*, I'm giving up and am asking for your help:

https://drive.google.com/open?id=1Y5...cL_vcpmg1eEWGo

This is a short segment from a long file, transferred directly from 16mm film. I was able to fix the dupes every 24 frames with DeDup, but I'm left with the combing.
If you separate fields, you can see it's progressive material, yet there's combing in every frame. Telecide(post=0) did nothing to help, and of course I don't want to run deinterlacing which would lose detail - I want to recover the progressive frames.

Can you figure out what's going on?

Thanks!

* Most of them spent on failing to get AviSynth + QTSource working on OS X via PlayOnMac/Wine, and on fixing the silly 24>25 conversion.

[poisondeathray]

I don't see any "combing" in the sample.

Or what are you describing as "combing" ?

There is some chroma ghosting, possibly from improper chroma handling upstream in the workflow. Or it might be your source filter

[binba]

Interlacing artifacts... they're all over the video, in the players and at the top&bottom edges of the advertising billboards.

[poisondeathray]

Originally Posted by binba

Interlacing artifacts... they're all over the video, in the players and at the top&bottom edges of the advertising billboards.

I don't see any.

I see compression artifacts, but no "interlacing" or combing artifacts

It might be your mjpeg decoder field swapping incorrectly

Try another source filter like ffms2 , lsmash

[binba]

Just realized you're probably looking at Google's mangled encoding.

Ignore it and use the download button in the corner to download and look at the actual video.

I attached 2 screen grabs, one with the original combing/interlacing and the other after throwing bobbing at it.

[poisondeathray]

No, I downloaded the original

Screenshots can take days to get approved. Can you upload to a different hosting site ?

[ChaosKing]

I also can't see any interlacing or combing artifacts, only compression artifacts. Opened it with lsmash in Vapoursynth.

EDIT: a quick encode with smdegrain https://www.dropbox.com/s/babb0l7oxp...l16mm.mkv?dl=1

EDIT2: I think I know what you mean. Sometimes it looks like interlacing but these a just odd looking compression artifacts

[poisondeathray]

The one I downloaded was "16mm-combing3.avi" , 44.9MB , mjpeg

You mentioned "AviSynth + QTSource working on OS X..." , that implies something MOV wrapped . What was the film transfer original format ?

[binba]

Sorry, this is silly, never I thought I'd be stuck in the "where is the problem?" phase this much. You guys are really trying to help and I'm perplexed why it's not showing... I'll just keep trying.

Here - combing all over:


And for comparison, if I were to bob it:


It looks identical everywhere I play it - on PC, Mac, VirtualDub, Premiere, QT7 Player. The AVI file is a direct (no-recompression) trim, from the original film transfer file as far as I know. Was given to me as that MJPEG (19GB for the full file).

[poisondeathray]

Originally Posted by binba

The AVI file is a direct (no-recompression) trim, from the original film transfer file as far as I know. Was given to me as that MJPEG (19GB for the full file).

Perhaps you inadvertently processed it somehow ? Maybe you forgot to use direct stream copy and had some filters?

Can you take a look at the sample sample you uploaded? Because it's definitely different characteristic-wise than your screenshot . And your screenshot isn't even contained in the sample

[binba]

Pretty wacky... I dug in deeper, and was able to confirm that libavcodec was introducing the combing artifacts.
If I open the AVI in QT7, or in VirtualDub with ffdshow[libavcodec], there’s combing.
If I open the AVI in VLC, or in VirtualDub with ffdshow/libavcodec disabled (and whatever decoder is built in), it’s clean.

Being a fresh install, my ffdshow/vfw settings were at their defaults and nothing funky was enabled; still, I tried to tweak anything that seemed relevant, and was unable to make libavcodec decode it cleanly.

So I settled for using ffmpegsource instead of AVISource, and so far it's working well.

It still begs the question, how would such artifacts be introduced from an otherwise-clean progressive video?

[poisondeathray]

Originally Posted by binba

Pretty wacky... I dug in deeper, and was able to confirm that libavcodec was introducing the combing artifacts.
If I open the AVI in QT7, or in VirtualDub with ffdshow[libavcodec], there’s combing.
If I open the AVI in VLC, or in VirtualDub with ffdshow/libavcodec disabled (and whatever decoder is built in), it’s clean.

Being a fresh install, my ffdshow/vfw settings were at their defaults and nothing funky was enabled; still, I tried to tweak anything that seemed relevant, and was unable to make libavcodec decode it cleanly.

So I settled for using ffmpegsource instead of AVISource, and so far it's working well.

It still begs the question, how would such artifacts be introduced from an otherwise-clean progressive video?

It's common back then with various mjpeg decoders. Many have a "swap field" option checkbox to enable/disable

You could use swapfields() in avisynth too if the decoder output the fields swapped. But it's important to analyze if that's really the issue by looking at the fields as you have