Awful moire and artifacts when down-converting HD to DVD

[matt9b]

I've been reading around and tried several ways to down-convert, without much success. I have filmed a documentary in HD that needs down-converting to DVD. I'm getting really bad artifacts such as 'moire'? on peoples' glasses. I'm not sure what the correct term is, but it looks really really bad.

Here is what I've tried so far:

Downconverting directly by rendering from the HD Sony Vegas project
Downconverting an HD file in After Effects
Downconverting an HD file in Sony DVD Architect

Whilst I've searched these forums, everything I've tried so far and read hasn't worked. Is there a tried and tested method to get HD to DVD without artifacts?

I've been working on this for days now and really would appreciate the help.

Thanks

 

[JamesRitson]

Hello,

You're probably seeing aliasing as a result of the universally bad job these programs do at resizing. Glasses in particular are very noticeable, especially on talking head subjects.

The solution may be to do your resizing in a separate program, which involves another step in your post production chain. As you're using Sony software I take it you're on Windows, which opens up the possibility of Avisynth. It may be a tough nut to crack at first, but it gives you a huge amount of control over how your video is handled.

If you want to go down the Avisynth route, you'll need a few things:

1) Avisynth itself
2) VirtualDub or VirtualDubMod (I prefer Mod, it's not been updated since 2006 but it works well)
3) A lossless (or near-lossless) codec, preferably a Windows-based one that works with DirectShow. If you don't have something like Cineform, consider UT video codec - http://www.free-codecs.com/download/Ut_Video_Codec_Suite.htm - it's very fast and efficient.


Export from your NLE to the lossless codec in a folder of your choice (if using the UT codec, you can choose between YUV and RGB, as it's video material you will likely be using the former).

Next, create a blank text document but save it with an .avs extension, so it's now seen as an Avisynth script. Make sure you save it in the same folder as the video for now. In this script, write:

DirectShowSource("Video.AVI")

Lanczos4Resize(720,576)

Note: I've assumed this is a PAL DVD so I've used PAL dimensions. If it's for NTSC delivery you will probably want 720x480. I confess I haven't really worked in NTSC formats so I can't help you there!

Replace Video.AVI with whatever you named your video file. Finally, open up the .avs script in VirtualDub/Mod, and your video should appear, albeit squished, as we've resized to a square aspect ratio.

Check your video for aliasing and other artefacts - if it's still bad, consider using a different method of resizing. You can see a basic list here: http://avisynth.org/mediawiki/Resize

Bicubic and Bilinear resizing are I think the ones most commonly used in NLEs and compression programs. They're softer but could help to lessen the aliasing problem. You might also want to try Spline or Blackman resizing. Every time you make a change in the script, you can refresh the video in VirtualDubMod by hitting F5. In vanilla VirtualDub I think it's another button (F3 maybe).


If you're happy with the result, find the Compression option under the Video header and choose a codec (best to just pick the lossless codec again). Once you've OKed that, go to File and choose Save AVI to save the new video. It will then render out.

Finally, you should be able to import the new video file into your DVD authoring program, or your NLE, to encode to MPEG2. Make sure you correct the aspect ratio so it displays properly (usually under "Properties" or "Interpret Footage").

Hope that's helped somewhat!


Extra note: you can cut the second export and re-importing out of the chain completely by using an external MPEG2 encoder. Check out a program called hcEnc - you can feed it Avisynth script files directly, and it has a single button press to ensure DVD compliant settings.

As an added bonus, by using this method, you can change the colour space to YV12 (4:2:0 sampling) within Avisynth, which will likely do a better job than what could be achieved through your NLE. This can help with colour-related artefacts, especially regarding the red channel. To do this, insert an extra line at the end of your .avs script:

ConvertToYV12

Give that to hcEnc, choose some sensible encoding settings, and hopefully the video quality will surpass that which you're getting from your NLE. I say hopefully because some differences may be subjective, and it can be an awful lot of extra effort if you feel the means don't justify the ends.

 

[matt9b]

Yikes! Thanks for the detailed reply. Very much appreciated, but wow that will take me a month to do all of that ! Yes it's aliasing is the word I was looking for. I guess there is no simple way to do this? Seems like a basic thing to want.. gah!

Thanks though for all of that. I do have Cineform.

I managed to resize it and VLC doesn't show any aliasing...! yippee!! But after burn it to DVD (without re-compressing), suddenly the aliasing appears on TV again. Very odd.

This is turning into a bit of a nightmare! I'll keep working on this but I'm running into over 100 hours so far just to get the thing burnt to DVD - almost the amount of time it took to make the documentary!