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Transcoding to 3K for edit - is this dumb?

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Nick RyanTranscoding to 3K for edit - is this dumb?
by on Dec 13, 2016 at 5:57:04 pm

First off, I recognize that most of you are probably running media pipelines that are much more bandwidth intensive than this, but if you can shed any light on our situation that would be great. This question has to do with downsampling resolution in order to preserve bandwidth.

To start, we shoot on GH4's (which lets you know where we are in life). 😊 We're not the world's best, but as every year goes by we push our equipment further and further and get better and better images out of our stuff.

The GH4's shoot 4K video at a 100Mb/s bit rate. We've been editing the footage natively in Premiere Pro for some time now, but have been often frustrated by how hard the h.264 codec is for our machines to edit. We're running Z820's, 2 x 2.4 Ghz 8-core processors, 128GB of RAM, with Quadro 4000's and Titan X's; but the machines still have to stop and think when trying to jump around the timeline or apply an effect or scrub through the h.264 footage.

After doing some tests, we discovered that Avid DNxHD, DNxHR, and Apple ProRes (true editing codecs), work MUCH better in the edit suite. We can scrub, jump around, and add effects to our hearts content and our workstations take it all in stride.

Now for the conundrum. Most of these editing codec bitrates are *higher* than what we're shooting in. If we downres to 1080 we can achieve comparable bitrates, but we'd like to retain the higher resolution of 4K to allow for reframing, cropping in, stabilization, etc. While we're recording at 100Mb/s, Prores LT is bumping us up to the mid 300's, and DNxHR is right up there with it. While we want the benefits of using Prores or DNxHR, we don't want to cut our storage space by 66% to do it. I could get happy with losing space if we were somehow gaining image data, but obviously all that extra data space is wasted.

Hence, our discovery: if we take our 4K footage and transcode to DNxHD LB, while downrezzing it to 2800x1575, we get a sort of happy medium. The bitrate is around 80Mb/s, and the resolution is still large enough to allow reframing, cropping, stabilization, etc. The footage plays/edits nicely on the timeline, and all would seem to be well with the world.

My question is, am I introducing negative effects here that I'm not aware of? Is downrezzing it to "3K" for editing, and then finishing at 1080 later going to make it look softer than just downrezzing it to 1080 right away? When you downres from 4K to 1080 you're working with an even 25% of the original resolution, which is what makes it look so sharp, right? I'm wondering if the random "3K" that it's interpolating for us while editing doesn't translate to 1080 quite as nicely. (Or am I overthinking this?)

Note: 2800x1575 is the largest resolution DNxHR will allow us to use while retaining a 16:9 aspect ratio. ProRes is not a viable option unless we find an easy way of transcoding into ProRes on PC's.

Any thoughts or feedback you have are welcome! Thanks!

Nick


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Blaise DourosRe: Transcoding to 3K for edit - is this dumb?
by on Dec 13, 2016 at 6:30:44 pm

Why not proxy your footage in 1080p with something like ProRes LT, and then do your final render with your full-res media? That's what a lot of folks do when they can't edit at full-res 4K due to high data rates. The same principle applies to media with heavy processor load due to compression.

To answer your question--yeah, it's kind of dumb. Sorry ☺ Most modern NLEs have a workflow that allows you to create proxy media for exactly the purpose you need.


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Alan LloydRe: Transcoding to 3K for edit - is this dumb?
by on Dec 13, 2016 at 7:40:34 pm

[Blaise Douros] "Why not proxy your footage in 1080p with something like ProRes LT"

Most likely because a Z820 is an HP (Windows) machine.


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Blaise DourosRe: Transcoding to 3K for edit - is this dumb?
by on Dec 13, 2016 at 7:58:33 pm

Okay Alan, then how about one of the other proxy formats that Premiere provides? Shall I draw your attention to the words "something" and "like," which are arranged in a particular order in the sentence above in such a way that they indicate the meaning "a format similar, but not necessarily identical to, ProRes LT, which is given as an example?"

Or, you could have read in OP's actual post that they have tried ProRes flavors, but rejected them as not working well due to their higher bitrate when working in 4K, thus implying that they might be one of the many people who have installed Quicktime and its codecs on their Windows machines, allowing them to use ProRes.

I can't believe that I actually had to explain any of this.


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Alan LloydRe: Transcoding to 3K for edit - is this dumb?
by on Dec 13, 2016 at 11:39:44 pm

Take a hike. A long one.


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Oliver PetersRe: Transcoding to 3K for edit - is this dumb?
by on Dec 14, 2016 at 12:27:11 am

Simply transcode your GH4 files to DNx codec on the HP. It can stay 4K and should play fine unless you have a very complex sequence. Working with native DSLR files is painful and causes all sorts of problems if you have to roundtrip the project.

- Oliver

Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com


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Blaise DourosRe: Transcoding to 3K for edit - is this dumb?
by on Dec 14, 2016 at 1:32:54 am

Wow. You really showed me.

Look, sorry if your feelings are hurt by my above annoyance. But it's not helpful to OP if you (a) don't take a second to read and comprehend his whole post, (b) do the same thing when reading my response, and then (c) miss the point of OP's post entirely by focusing on responding to an insignificant detail of my response because of (a) and (b).

If you're just going to nitpick someone for pointing OP in the general direction he has asked for, then don't expect to be treated as anything but a troll.

But no, I guess I'M the one who needs to take a hike out of YOUR teeny tiny corner of the internet.


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