Unusual Aliasing on "The Men Who Stare at Goats" BluRay

[Blue_MiSfit]

Hey folks,

I'm working on encoding The Men Who Stare at Goats, and have noticed a nasty and unusual aliasing throughout the entire movie.

It's difficult to describe, but looks similar to another title I posted about here:

http://forum.doom9.org/showthread.php?t=144316

Here's a screenshot of how the issue manifests on text. Note also the gunky chroma inside the white text


And another screenshot example. Look at the flag and diagonal edges of the house:


And of course, here's a proper sample:
http://www.mediafire.com/?nyynmyyymm2

What do you guys think? Noting the similarity between this and the issue I had with "Shine a Light", I tried the MT_Convolution lowpass filter suggested by *.mp4 guy. This reduced visible aliasing in live action scenes, but demonstrated massive ringing around text. It also affected global luma levels, but I remember that being discussed in my old thread.

I tried the same brutal method as before - turnright.nnedi.turnleft, but this doesn't remove all the aliasing, and kills details / sharpness.

Perhaps a different FIR filter design can fix this as well? I do wish I better understood the construction and function of FIR filters.

~MiSfit

[IanB]

At first glance it look like the V chroma channel is shifted, leading to green fringes on the left, red fringes on the right of objects. I would not call this aliasing. I would call this faulty encoding or decoding. (1st try a different decoder)

Use something like this to analyse how the chroma planes are related :-

...src...
Y=Greyscale()
U=UtoY().PointResize(Width(Y), Height(Y))
V=VtoY().PointResize(Width(Y), Height(Y))

Interleave(Y, U, Y, V)

You are looking for how edges of objects align across the planes.

If this hypothesis is correct and you estimate how much to shift back, use something like this :-

...src...

Y=Last

Ux=0.0 # U right shift amount
Uy=0.0 # U down shift amount
Y.UtoY()
U=Spline16Resize(Width(), Height(), Ux, Uy)

Vx=-1.5 # V right shift amount, -ve -> shift left
Vy=0.0 # V down shift amount
Y.VtoY()
V=Spline16Resize(Width(), Height(), Vx, Vy)

YToUV (U, V , Y)

This abuses the resizer as a subpixel shifter ...

[Blue_MiSfit]

Thanks for your time IanB!

I decoded the source (and created the sceenshots) using DSS2 (Haali + CoreAVC 2.0).

I'll try FFMS2 and your suggestion for playing with chroma plane alignment.

I agree this looks quite promising for the chroma issues, but what about the stair stepping (aliased) diagonal edges?

Thanks again!
~MiSfit

[Gavino]

Originally Posted by IanB

V=Spline16Resize(Width(), Height(), Vx, Vy, Width()+Vx, Height+Vy)

Why isn't it
V=Spline16Resize(Width(), Height(), Vx, Vy, Width(), Height)

or, the same thing,
V=Spline16Resize(Width(), Height(), Vx, Vy)

[IanB]

@Gavino, Yes, oops

@Blue_MiSfit, this looks like shitty upsizing, return the disk and get your money back.

[Blue_MiSfit]

@IanB:

Unfortunately this is a BluRay from a studio I'm expected to transcode and put on a VOD service... I'm hoping some resolution can be found.

Otherwise I'll just encode it as-is

[Lyris]

I've seen these exact same problems on a UK disc from Entertainment In Video. Not sure who did the encode or what encoder, but I thought my projector's focus was off when I first saw the "misconvergence" (what actually just turned out to be weird coloured fringing in the encode itself).

[IanB]

Originally Posted by Blue_MiSfit

Unfortunately this is a BluRay from a studio I'm expected to transcode and put on a VOD service... I'm hoping some resolution can be found.

Are you are sufficiently in the loop to find out how this disc was mastered?

Otherwise I'll just encode it as-is

Yes, just fix the chroma aberrations, and continue from there.

Are you re-encoding at the original resolution or smaller?

I guess I should have asked earlier, what is the unscaled horizontal resolution of the source? 1920? 1440? other?

[Blue_MiSfit]

The BluRay disc is 1920x1080, not to say that it didn't come from an HDCam or DVCProHD. I'd suspect some subsampled format, given the atrocious processing that was obviously performed at some stage.

I'm not really in the loop enough to see how the disc was mastered, but I can possibly request a ProRes or 80mbps MPEG-2 mezzanine file. I'd rather not, since this usually means spending more money, and this movie isn't a huge new release. Maybe they can send me the master tape, we've got the decks to capture it.

I'l be re-encoding to 1080p, 720p, and 480p (3 bitrates each resolution)

~MiSfit