letterboxed 4:3 to anamorphic 16:9

[colinb]

I have a 4:3 PAL VOB file containing 16:9 material which had been scaled down and letterboxed so that there are wide black stips above and below.

I'm considering converting this to "real" 16:9, probably by using a Avisynth script to crop out the black bands and scale the image up to real 16:9 filling the whole 720x576 frame (PAL).

However, scaling up and re-encoding seems bound to reduce the quality somewhat.

Has anyone tried doing this and found it worthwhile, or would I be wasting my time?

If it's possible to get good results, does anyone have a script for doing this, and possibly reducing the effect of scaling up the mpeg artefacts.

[Kika]

Yes, you are wasting your time...

[FlimsyFeet]

Not necesarily, because scaling during post processing before encoding can give better results than your TV scaling.
http://forum.doom9.org/showthread.php?t=67273

however, as the image has already been scaled down the damage has already been done!

[Didée]

The usual rule of thumb is that you won't gain anything by re-encoding & upsizing from letterboxed to anamorph, but will only degrade quality.

However I dare to say that rules of thumb are just rules of thumb, thus not necessarily always true. Sometimes even wrong.

sample (http://home.arcor.de/dhanselmann/_samples/LOST_comparison%232-2.mkv), sample (http://home.arcor.de/dhanselmann/_samples/nibel_comp3_(crystality).avi), sample (http://home.arcor.de/dhanselmann/_samples/nibel_comp2_(crystality).avi), and sample (http://home.arcor.de/dhanselmann/_samples/nibel_comp1_(crystality).avi).

Also look here (http://forum.doom9.org/showthread.php?s=&threadid=70916&perpage=20&pagenumber=7).

Perhaps it's a waste of time ... but at least, it's a nice one, then. ;)

[SirCanealot]

Lanczos4Resize >>>>>>> my TVs

All my TVs upscale letterbox by stretching the TV's image out. That is, the image and the lines. Scanlines look possitively huge on NTSC LB material.
If you're running on these sort of TVs, then pre-resizing is MUUUUCH better than letting the TV or DVD player do it (none of my DVD players will resize LB material...).

Anyway, if you're doing a proper re-encode (sharpening+denoising), the upscale won't exactly harm quality, but give your end-source more resolution to work with :D

[colinb]

Thanks for your comments everyone. I think I'll give it a try.

So effectively I'll be cropping the black bars from top and bottom and then stretching whats left in the vertical direction ONLY (no resizing in the horizontal direction because the letterboxed material is 720 wide and the anamorphic widescreen result will also be 720 wide).

I wondered about denoising or other filters to reduce the original's mpeg artefacts and help the second encoding produce better quality.

Has anyone got a ready made script that I can use as a starting point?

[Wilbert]

I took the liberty of correcting the title. I hope you don't mind :)

[Piper]

@colinb

I've been wondering about doing much the same thing with my captures. I've done the following - using output from FitCD to determine resizing, which is essentially what you're doing.

Source is analogue capture at 720x480, YV12.

AVISource("c:\capture\capture.avi").Crop(0,60,0,-60,align=true)

#Deinterlace
KernelDeint(order=0,threshold=0,sharp=true,twoway=true)

#Denoise
LRemoveDust(17,1)
UnDot()

#Resize
LanczosResize(704,480,0,0,720,360)
AddBorders(8,0,8,0)

[colinb]

Thanks for that. It's not really clear why you would want to do any horizontal scaling to make room for 8 pixel borders, though. If your original material is 720 pixels wide then surely you would be better off preserving the 720 pixels across the screen and just do the stretching/interpolation in the vertical direction?

I notice that there is a HUGE thread here entitled "iip: Integrated Image Processor, e.g. DVD -> 720p HDTV" which seems to be a similar stretching procedure - perhaps I should take a look at that.

Given that my source material is from a PAL VOB, do I need to do any special processing of it before scaling due to the color info only being present on alternate lines?

[scharfis_brain]

@Piper: why kerneldeinterlace?

at least, you WILL loose half of the motion information as well as near half of the image resolution.

better use this script:
(it will retain the interlacing)

AVISource("c:\capture\capture.avi").Crop(0,60,0,-60,align=true)

#Deinterlace
assume?ff() # replace ? with t or b, according to the Fieldorder of your source
tdeint(mode=1,type=3)

#Denoise
LRemoveDust(17,1)
UnDot()

#Resize
LanczosResize(width,480)

#Reinterlace
assumetff()
separatefields().selectevery(4,0,3).weave()

[Piper]

@colinb: I agree. What I wanted to do there was to provide an example of what FitCD would come up with as I've seen it used in this context elsewhere.

@scharfis_brain: I thought about removing the actual deinterlacing & denoise lines and leaving only the comments as those weren't the focus of the thread, but in the end I left them in. Had I commented them out however, I wouldn't have seen your suggestion! Thanks for that. :)

I've traditionally used LeakKernelDeint because it's just so fast. I freely admit the settings shown above are somewhat "destructive". ;) For deinterlaced output what would you suggest?

Back to letterbox to anamorphic, on same 720x480 analogue source.

AVISource("c:\capture\capture.avi").AssumeTFF().Crop(8,60,-8,-60,align=true)

AddBorders(8,0,8,0)
LanczosResize(720,480)

This more to our liking?