HD to SD conversion “flicker free” with DaVinci?

[Helge Løken]

I’ve looked at SR but not directly compared it to Resolve. SR scaling is really good, but MPEG Streamclip is nearly as good (excpet not doing 709 to 601 conversion). From the top of my head I imagine Resolve is up there… (although not on interlaced material).

[Ola Haldor voll]

I’ve had the chance to test a little today, and I had the opportunity to check it against MPEG Streamclip, Adobe Media Encoder and Compressor. DaVinci won by far.

Seems I’ve got this sorted out, and I’m looking forward to the job the next few days.

Thanks for all your tips and tricks, guys!

[Blase Theodore]

Hopefully I’m not thread-jacking this (as I believe the answer is directly pertinent to your job.)

In the event that you’re working with an interlaced HD format and need to go to an SD interlaced format, then the question falls to how resolve samples the frame.

If it samples whole frames (1/30th), sampling an interlaced HD frame would actually be counterproductive, as the sampled pixels would basically be averaged against 2 different points in time. There’s no correlation I’d see between an HD scanline, and what eventually becomes an SD scanline.

If thats the case, would converting to a progressive format right off the bat result in a better image?

If it samples each field (1/60th), then you have something analagous to:
HD_60i can effectively downsample to SD_60p, which can effectively become 60i.
HD_30i can effectively downsample to SD_30p, which can effectively become 30i.

If that’s the case, then there could be artifact issues with how 2 fields independently scaled and processed line back up with each other at the end.
An early-on progressive workflow might theoretically improve that as well?

Going with the assumption that Resolve has a good downsampling algorithm, has anyone done this comparison test for HD interlaced material?:

• Progressive material in resolve (pre-rendered through compressor, field control: best) rendered out as SD interlaced.
• Interlaced material in resolve (checkbox for interlaced) rendered out as SD interlaced.

If I have my facts spun around, please correct me.

[Ola Haldor voll]

Interesting you should bring this up. As a matter of fact, one of the clips I tested was shot in HD 50i. It didn’t look bad at all when I had used DaVinci to downscale it.

[Margus Voll]

So we could conclude that Resolve does it well.

Nice!

—

Margus

https://iconstudios.eu

[Ola Haldor voll]

OK guys – the job is done, and I have one more happy client to add to my portfolio.

Onlining this was a b.. you know the word. I’ve never had the question to downscale from HD to SD before, so I learned a lot about this.

Even though DaVinci does a very good job with the down scaling, there’s still some things it just didn’t let go of, so for the most problematic projects (There was 21 videos with interview/artist presentations for a song contest) there was one common error: it was shot 1080 50i. This means DaVinci was slower than usual while adjusting the colors, and I didn’t get playback stutter free because of all the nodes I had to use on some of the clips, thus I had to render..

I rendered as PAL the first time – it looked good, but not as good as the SD downscale I had the Decklink card do while I was in DaVinci.

The second time I rendered in HD, played it from BMD Media Express and fed the SDI stream to my other Mac and recorded it in BMD Media Express – so the Decklink card did the downscaling. And it was just flawless and very beautiful in regards of flickering.

On top of that, for the conversion to IMX (with mastered sound..) I used Compressor and Frame controls ON with BEST motion estimation and deinterlacing. Then the images became just superb. Sharp, yet no flickering at all.

We did this for a few of the sequences shot on 5D too, to relax some details in shots like tiny details on jackets or strands of hair that went all over the place, and made the image seem “busy” on the CRT monitor.

It took us hours to find this workflow, but I’m happy we investigated so much time in this. I’m a smarter man now, and I really, really, really hate interlaced material!

Thanks for all your support and input. It’s been priceless!

[Uli Plank]

Thanks for the detailed information.

So, if I understand you well, the best quality if you want interlaced SD from interlaced HD was the downscale by the Decklink card, right?

De-interlacing was best with Compressor with all the bells and whistles on, right?

I know the 5D is a different subject with all it’s aliasing…

If the Panasonic 101 is any good, I hope that will be a thing of the past, sigh!

Director of the Institute of Media Research (IMF) at Braunschweig University of Arts

[Ola Haldor voll]

That’s right. HD playback on one Mac with output to SD on the Decklink card, and record on the second Mac in SD. That did the trick.