Downscaling from 2160p

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Fogdood
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Downscaling from 2160p

Post by Fogdood » Fri Oct 19, 2018 2:58 pm

I have a set of MKVs of a TV series. It's in UHD 2160p. I want to convert them to DVD. I used my usual settings & the Lanczos filter, medium project (5 episodes per disc), 5GB output size, single pass, high quality, removed all but one subtitle track & normalized the 5.1 audio track. The processing took almost 24 hours on a machine with quad 2.8Ghz processors & 16GB of RAM. The result was horrifically bad. The worst I've ever gotten. Virtually every frame was huge blocks of shades of grey with massive pixellation with motion. The audio was fine & seemed in sync with what video I could identify. The original files play fine in MPC-HC. I concluded I may not have been giving it the best options, so I opted for 9GB output & tried it again. Same result, though much of it looked fairly normal, now.

I'm trying it again. This time, with 2 pass encoding & I'm doing only one episode, as a test. It has at least 5 hours to go.

My suspicion was that the Lanczos filter may not be the best choice, though I was under the impression it was one of the very best for downscaling.

Should I be using a different filter? Is my hardware just too under powered for this?

Any help & pointers would be appreciated.

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yoyo57
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Re: Downscaling from 2160p

Post by yoyo57 » Fri Oct 19, 2018 8:05 pm

I have tried a couple of times and failed, maybe not supported

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Fogdood
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Re: Downscaling from 2160p

Post by Fogdood » Fri Oct 19, 2018 9:48 pm

Two pass encoding didn't help the least tiny bit. This may not be an option with CXD7.

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yoyo57
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Re: Downscaling from 2160p

Post by yoyo57 » Sat Oct 20, 2018 1:37 am


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Fogdood
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Re: Downscaling from 2160p

Post by Fogdood » Sat Oct 20, 2018 3:24 pm

I don't get it. I would think downscaling would be far more reliable & simpler to achieve than upscaling, but it sure hasn't turned out to to be the case, in this instance.

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JJ
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Re: Downscaling from 2160p

Post by JJ » Sat Oct 20, 2018 5:04 pm

Downscaling from 3840x2160 to 720x480 is not an easy task.
Details on original make it almost impossible to reduce properly.
3840 to 720 factor of 5.33
2160 to 480 factor of 4.50

Might be impossible task to produce good quality as proportions change as well as huge resolution drop.
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Fogdood
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Re: Downscaling from 2160p

Post by Fogdood » Sat Oct 20, 2018 8:37 pm

Out of desperation, I pulled up a transcoder I've used with great success, in the past. I re-encoded one of the files from 2160 to 720. It played just fine, but it will take almost 20 hours to re-encode 4 more episodes. Once they're all done, I'll see how CXD handles the 720 versions. No reason it shouldn't work, though there will certainly be quality issues. As long as it's watchable, I'll be satisfied. I could have used the transcoder to go straight to DVD, but it isn't as flexible as CXD, when it comes to options.

Yep: Transcoding BEFORE CXD worked like a charm & the quality (using 5GB DVD & 2 pass encoding) is fine.

reddwarf4ever
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Re: Downscaling from 2160p

Post by reddwarf4ever » Thu Sep 05, 2019 10:25 am

Hi

Interesting, which transcoded did you use ? Also why didn’t you go to 1080 ? Because 720 is a big drop in quality

Thanks

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