Is this massive combing?

[pedx1ng]

Can you take a look at this still:

Eyes Wide Shut screen grab (mywebpages.comcast.net/novanus/temp/ews1.jpg)

And tell me if it is big combing artifacts that I am seeing?

I am trying to re-encode a 1080i stream to 720p. Here is my AVISynth script:


LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\Decomb521.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\mpgdec\DGDecode.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\UnDot\UnDot.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\fdecimate101\FDecimate.dll")

MPEG2Source("E:\_VidCap\Working\eyeswideshut.d2v",idct=5, moderate_h=25, moderate_v=50, cpu2="xxxxoo", iPP=true, showQ=false)

Telecide(order=1,guide=1,post=2,show=false)
Decimate()

Crop(4,4,-4,-12)
UnDot()
LanczosResize(1280, 720)


What am I doing wrong? Thanks.

[pedx1ng]

No one can help? Can someone at least say whether the artifacts in the picture is combing?

[neuron2]

What artifacts? We're not mindreaders! Ideally, circle it on your JPEG and tell us in words. I don't see any combing on that screenshot. Jeez, you didn't even tell us if that is the input or output screenshot!

[dbloom]

There are some interlacing artifacts in parts of the picture (especially on the faces in the foreground). The frame is probably overcompressed and perhaps the grab is from two fields in different coded frames. Even if you didn't do this, the movie may have been recompressed from an mpeg-2 source before broadcast, thus creating mix of fields from different frames.

I'd inverse telecine (if needed/possible), then run a very strong field *blending* deinterlacer. Blending causes fuzziness, but does not discard any picture information, so it is the best deinterlacer. Don't resize to half height then size back up, or use a field-discarding deinterlacer, as that is more lossy.

Deinterlace before you convert to 720p, of course.

Suggested modification to AVS script:


LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\Decomb521.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\mpgdec\DGDecode.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\UnDot\UnDot.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\fdecimate101\FDecimate.dll")

MPEG2Source("E:\_VidCap\Working\eyeswideshut.d2v",idct=5,
moderate_h=25, moderate_v=50, cpu2="xxxxoo", iPP=true,
showQ=false)

Telecide(order=1,guide=1,post=2,show=false)
Decimate()

FieldDeinterlace(full=true,dthreshold=3,blend=true)
Blur(0,.3) #if you're resizing down anyway, it's a great
#time to blur to get rid of those artifacts
#note the 0,.3 as we are only blurring in the
#vertical direction, so we can reduce leftover
#interlacing without harming horizontal detail

Crop(4,4,-4,-12)
UnDot()
LanczosResize(1280, 720)

sharpen(.05,.1) #sharpening after resize also helps a lot,
#otherwise the picture is softer than it
#should be

[pedx1ng]

neuron2: Please forgive me for being quite the newbie at this stuff. I have done quite a bit of reading of help files and posts in this forum before posting, but I am as confused as ever. I thought that if some experts looked at that pic they could easily see if there were tell-tale signs of problems.

dbloom: I am thinking maybe my source isn't as clean as it should be. An upconvert maybe? The details just aren't there compared to some other 1080i material I have. There seem to be a lot of artifacts as you say.

But I am thrown by your use of FieldDeinterlace after Telecide in the new script. I have read this excerpt from the help file:

This filter provides functionality similar to the postprocessing function of Telecide. You can use it for pure interlaced streams (that is, those not containing telecined progressive frames). (The name refers to the fact that field mode differencing is used.) Do not use FieldDeinterlace after Telecide because the same functionality is built into Telecide.

sigh, maybe I should just throw it into AutoGK and see what happens. I wanted to process it manually though to have more control over the output.

[dbloom]

Originally posted by pedx1ng
neuron2: Please forgive me for being quite the newbie at this stuff. I have done quite a bit of reading of help files and posts in this forum before posting, but I am as confused as ever. I thought that if some experts looked at that pic they could easily see if there were tell-tale signs of problems.

dbloom: I am thinking maybe my source isn't as clean as it should be. An upconvert maybe? The details just aren't there compared to some other 1080i material I have. There seem to be a lot of artifacts as you say.

But I am thrown by your use of FieldDeinterlace after Telecide in the new script. I have read this excerpt from the help file:



sigh, maybe I should just throw it into AutoGK and see what happens. I wanted to process it manually though to have more control over the output.

Basically, I'm throwing on a superstrong deinterlacer. I guess you could do it in Telecide but then decimate and all...actually, neuron2 would probably know more about it. Whenever I use AVISynth, I end up having to look up every parameter, and it always takes so long...:P.

The interlacing is probably caused by your cable company reencoding the signal to a very high compression. This causes interlacing artifacts on fields combined from separate encoded mpeg-2 pictures from their source stream. Or maybe the cable company is IVTCing (poorly).

[neuron2]

Originally posted by pedx1ng
Please forgive me for being quite the newbie at this stuff. I have done quite a bit of reading of help files and posts in this forum before posting, but I am as confused as ever. I thought that if some experts looked at that pic they could easily see if there were tell-tale signs of problems. And still you've not answered any of my questions! I can't help you if you just ignore what I say.

[dbloom]

Originally posted by neuron2
And still you've not answered any of my questions! I can't help you if you just ignore what I say.

I can't get the image to load (my DNS is being stupid again), but if it works for you, the interlacing is primarily in the flesh tones of the faces in the foreground. You need either a very sharp monitor (LCD ideally), or to zoom in, to notice it. Good eyes don't hurt either.

The frame's motion isn't interlaced, but the flesh tones alternate slightly every other vertical line.

[neuron2]

OK, thank you.

Apparently, Telecide missed a field match and then postprocessed the frame. Field matchers are not perfect. If it happens on every frame or many of them, then it would be worth looking into. But this is imperceptible at normal size and play rates.

[dbloom]

Originally posted by neuron2
OK, thank you.

Apparently, Telecide missed a field match and then postprocessed the frame. Field matchers are not perfect. If it happens on every frame or many of them, then it would be worth looking into. But this is imperceptible at normal size and play rates.

I think his screenshot is actually from BEFORE the video is run through AVISynth. He's asking why there is combing in the details of a progressive frame (there is no motion combing, there are just small combing patterns on minor details, like compression artifacts).

The screenshot is 1920x1080, and it would have been 1280x720 had it been run through his AVISynth script.

[neuron2]

It would be nice if pedx1ng would give us the information we need to help him.

If it is the source frame, then he may have captured a pulled-down frame, and that combing will be removed by Telecide. But the combing has the look of having been passed through a thresholded deinterlacer, because parts are combed and parts not, and that doesn't correlate with motion, it seems.

[pedx1ng]

Originally posted by dbloom
I think his screenshot is actually from BEFORE the video is run through AVISynth. He's asking why there is combing in the details of a progressive frame (there is no motion combing, there are just small combing patterns on minor details, like compression artifacts).

The screenshot is 1920x1080, and it would have been 1280x720 had it been run through his AVISynth script.

OK, let me start over again.

Here are two screen grabs, OUTPUT frame from VirtualDubMod using the script I will paste below. Source is 1080i transport stream.

Full image with areas circled:
http://mywebpages.comcast.net/novanus/temp/ews2.tif

A cropped portion:
http://mywebpages.comcast.net/novanus/temp/eyesframe2_crop.png

Here is the AviSynth script I used.


LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\Decomb521.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\mpgdec\DGDecode.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\UnDot\UnDot.dll")
LoadPlugin("c:\Program Files\AviSynth 2.5\plugins\fdecimate101\FDecimate.dll")

MPEG2Source("E:\_VidCap\Working\eyeswideshut.d2v",idct=5, moderate_h=25, moderate_v=50, cpu2="xxxxoo", iPP=true, showQ=false)

Telecide(order=1,guide=1,post=2,show=false)
Decimate()

Crop(4,4,-4,-12)
UnDot()


When I do resize down or use the script provided by dbloom the artifacts I was seeing do seem to go away. I just wanted to know if I was doing something wrong or if it was just a problem with my source video. From what I've read by dbloom I'm assuming it is a problem with the source video.