Time Interpolation and its effect on YouTube compression

[philipb14348381]

Hey everyone,

my problem is the following: I am trying to export high motion gameplay and upload it to YouTube. I have already disabled motion blur within the game because I heard it diminishes the quality once YouTube's algorithms are finished playing with it but some (seemingly random) parts of the video are much more blurry than the original. I don't know enough about Premiere Pro to be sure but I have a suspicion that it has something to do with the time interpolation Premiere applies. You see the gameplay itself is 60FPS and the edited video is rendered as such but I have an intro in there as well that is 30FPS (although Premiere reads the image sequence as 29.97FPS but that's another matter). I don't recall having THIS serious an issue with YouTube's compression before I upgraded to the latest version of Premiere which is (I believe) when the option was removed to disable frame blending. Could someone tell me if I'm on the right track here and possibly if there is a way to resolve this besides going back to an earlier version of Premiere?

Any help would be much appreciated!

For reference here are my current export settings:

Frame Rate 60FPS

Field Order Progressive

Aspect Square Pixels(1.0)

TV Standard NTSC

Profile High

Level 4.2

Render at Maximum Depth checked

Bitrate Encoding VBR, 2 pass

Target Bitrate 20/25 (I tried multiple values, issue persisted)

Maximum Bitrate 61.25

Use Maximum Render Quality checked

Time Interpolation Frame Sampling (since premiere doesn't exactly explain what the difference between the three options here is I just left it as the default)

[jstrawn]

I think you're confusing 'Time Interpolation' with 'Optical Flow'. 'Time Interpolation' is an umbrella term we started using in 9.1 to categorize the various options within the UI. Optical Flow is a new feature for 9.1. 'Frame Blending' and 'Frame Sampling' are still there, inside a new 'Time Interpolation' pulldown UI, along with 'Optical Flow'.

Optical Flow will not inherently blur your video. It's just interpolating missing frames instead of just duplicating (and maybe blending, if that's what you chose) them to make the speed change look more realistic. If you want to do it the way you did before 9.1 just choose Frame Blending or Frame Sampling.

For more detail on the UI and functionality of Optical Flow, go here: Optical Flow Time Remapping – Tips & Tricks for Best Results | Premiere Pro work area

[philipb14348381]

Thanks for the response. I'm aware they're not the same. As I said I'm not clear on what exactly the different KINDS of time interpolation do. Well I have had Frame Sampling selected until now so if you don't think that is the problem, what could it be?

[jstrawn]

Philip Braunen wrote:

Thanks for the response. I'm aware they're not the same. As I said I'm not clear on what exactly the different KINDS of time interpolation do. Well I have had Frame Sampling selected until now so if you don't think that is the problem, what could it be?

Frame Sampling - samples the pixels within a frame and then duplicates them into new frame(s) as needed to get the slo mo effect (e.g. at 50% speed each frame is duplicated one time, but at 20% they are duplicated 4 times (for a total of 5 repeated frames

Frame Blending - does the same as frame sampling and it blends the pixels between adjacent frames to make the motion look smoother than just copying might

Optical Flow - does not just duplicate frames for speed changes, it actually creates new frames as needed by interpolating between two real frames incrementally as needed.

But optical flow (OF) does not actually know the difference between a foreground subject and the background. It's all just pixels, so there is an inherent limitation to this sort of interpolation (not just the OF feature in PrPro) where if there is a lot of movement and/or if it's hard to clearly differentiate between foreground and background, then you may see areas of occlusion marked by unexpected artifacts and pixelization. To know if this is part of your problem you should make sure to build render preview files (choose render effects in to out after applying OF) which will then render the high quality OF frames and show you what you will see at export. If there is not a major problem at that point then you can be pretty sure that OF is not causing the export problem you're seeing. In that case, my next guess would be that is has something to do with putting 60 fps clips into a 30 fps sequence and then rendering it all out as 60 fps. But I can't say that for sure without trying it with your project + media myself and I'm not even sure I understood your steps right anyway.

[david@harveywetdog]

Thanks for this I was also wondering which was the best option to use for time interpolation and this explanation has answered my question. Can you just explain what  "(choose render effects in to out after applying OF)" means please?

[jstrawn]

David Robinson wrote:

Can you just explain what  "(choose render effects in to out after applying OF)" means please?

1. Apply a speed change (or time remapping) to a clip

2. Make sure Time Interpolation is set to 'Optical Flow' (the render bar will turn red)

3. Go to Sequence > Render Effects In to Out (or hit Enter, which is the default shortcut)

Note: if you have the work area bar enabled the menu item may say 'Render Work Area bar' instead