Aliasing from HD Source

[mionis]

Hello All

Recently, our clients have been delivering 1080 23.98 source.
We've been using CCE-3 and have been happy with most of our result.
However, with high contrast areas in the picture. We noticed a pronounce amount of alaisng along the edges. We're curious if there's any approaches we can take on thiis. Maybe a setting in CCE or maybe something w/AviSynth?

Our settings have been B-Spline, Progressive, 6pass VBR, Picture qaulity is selcted as Defualt with modication to ZigZag and Progrressive.

Any thoughts would be welcomed

Thank You

[Lyris]

Have you tried the different downscaling algorithms? Linear interpolation should give an overall softer look.

[Mug Funky]

no need for 6 passes... 2 is fine. in fact, if your DVD is not pushed for space or your program is short, you can do 1 pass CBR at your max bitrate and get pretty much as good as can be put on DVD (until x262 gets completed...).

if your source is progressive, you can enable the vertical part of the lowpass feature. this'll blur enough to prevent the strobing effect on a CRT.

[mionis]

We've played with the various down-scaling approaches. So far B-Spline has worked well. But I'll take another stab at Linear interpolation.

I'll try the vertical part of the lowpass setting and see the results. Do you have a recommend value for me to start off with?

Thank you guys for your help

[TheSkiller]

Actually I would suggest to stay away from all kinds of low-pass filters that CCE offers, all they do is blur the picture.

if your source is progressive, you can enable the vertical part of the lowpass feature. this'll blur enough to prevent the strobing effect on a CRT.
Strobing effect? Strobing (stuttery motion) is caused by the lack of temporal resolution (because it's progressive) — blurring the lines vertically won't help. The only thing that will do is reduce or eliminate line twittering in totally static AND high vertical frequency parts of the video, something you should't do if you're not sure you need it.

Edit: Better downscaling could be archived with AviSynth...

[mp3dom]

Just as a note... if you fed an HD source to SP3, does it change the color primaries from bt709 to bt601 (the 'colormatrix' work)? If not, it's completely useless to downscale in SP3 unless the source is already in bt601 (kinda strange for a true hd source)

[Lyris]

Actually I would suggest to stay away from all kinds of low-pass filters that CCE offers, all they do is blur the picture.

Agree 100%. Routine Lowpass filtering ruined the DVD format. It was capable of so much more yet all we got was blur, blur, blur.

I think by Strobing, Mug Funky was talking about inter-line twitter. I find that to be a non issue on CRT for the most part.

[GodofaGap]

I think by Strobing, Mug Funky was talking about inter-line twitter. I find that to be a non issue on CRT for the most part.
Personally, I find it a very big issue. It's pretty common to see DVB with twitter here.

[mionis]

If you're using AviSnyth, is there a method better than B-Spline for the down conversion? Also, CC-E will change the color primaries from 701 to 609. However, if I use AviSynth does it have a utilities to perform this conversion as well?

[TheSkiller]

If you're using AviSnyth, is there a method better than B-Spline for the down conversion?
Well, since CCE's B-Spline seems to cause aliasing/jagged edges, there's pretty much a ton of different resizers in AviSynth to choose from which will all easily do a visually more pleasing job of downsizing.
For a sharp and accurate downsize without ringing you should try Spline16Resize() (my personal favorite).

Also, CC-E will change the color primaries from 701 to 609.
Have you visually checked that or did you just look at the flags of the resulting MPEG2 video? Edit: By the way it's 709 and 601. ;)


However, if I use AviSynth does it have a utilities to perform this conversion as well?
Sure, ColorMatrix(). :)

[poisondeathray]

was there aliasing in the HD source before the resize ? or did you only notice after downscaling ?

[kolak]

601/709 color space issue is not that simple to solve. Sometimes conversion may not be needed- lots depends on the player. In most cases DVD gets upscaled and TVs see HD signal- not SD.
So, what color space should it be :)?


Andrew

[Biggiesized]

Cinemacraft encoders seem to have botched rescaling algorithms. Even their spline filters end up with lots of aliasing.

I'd pre-process with another application and then feed CCE SP3 your 720(704)x480p YUY2 AVI source file.

[MilesAhead]

...
For a sharp and accurate downsize without ringing you should try Spline16Resize() (my personal favorite).



Glad to see I'm not alone. I get excellent results going from 1080 .mkv to dvd using Spline16Resize() and HC Encoder best profile 2 pass. Played back on an upscaling player it's tough to distinguish the dvd from the .mkv played on an HD set top box.

http://www.smilchat.net/smileys/moyens3d2/3dmilitaire.gif

[mionis]

was there aliasing in the HD source before the resize ? or did you only notice after downscaling ?

There was no aliasing on the HD source. Just very high contrast like blades of grass. The encoder generally does well on down-conversion of HD, but fails on high contrast shots.

The CCE-SP3 supports HD resolutions but I hadn't found anything in the manual stating 709 converting into 601 (excuse the minor moment of dyslexia earlier) . However, we did perform a test and compared the MPEG to the HD Master. There was a significant change in the values visually. The only info MediaInfo gave was 4:2:0 and 8bit. No color primaries information was seen. So I'm assuming SP3 is converting this.
Unless there's a better tool reading MPEG values?

Overall, I will play w/AviSynth and try it out. Using the Spline16Resize and ColorMatrix plug-in.

I'll post my results in a couple of days.
Thanks