29.97i to 23.98p
Have you ever needed to convert older standard-definition footage from 29.97i to 23.98p for use in a new project? Resolve is no Alchemist, but it can get the job done in a pinch. Read below for the best practices approach to converting your footage for use in new films or documentaries.
Setup Your Project
I would recommend creating a new project just for conversions. First up, we will set up the Mastering Settings. Set the timeline resolution to 720x486 NTSC. Are you working in PAL? If so set this to 720x576. All the other steps will be the same, but I will assume you are working with NTSC(North America and Japan) files going forward.
Usually, we work with square pixels with a pixel aspect of 1:1 for HD video and higher. Here we need to change the pixel aspect to conform to the older standard of 0.9:1. Remember when you were young and pushed your face right up against that old Zenith TV set. Perhaps you noticed the RGB rectangles, not squares, that made up the image. The 4:3 standard definition setting accounts for that.
Finally and most importantly, we set the frame rate to 23.976, which is what we want for our output.
At this point simply dragging a clip onto a timeline will result in it being converted to 23.98, but why does it look so steppy and bad? We need to tell Resolve to use high-quality motion estimation. This optical flow setting is the same engine that makes your speed effects look smooth. By setting it on the project page we declare the default method for all time re-mapping to use the highest quality frame interpolation. Including frame rate conversions.
Leveling the Playing Field: 29.97i to 29.97p
Technically 29.97i has a temporal sample rate of 59.94 half resolution(single field) images per second. Before we take 29.97 to 23.98 we need to take the interlaced half-frames and create whole frames. The setting we can engage is the Neural de-interlace. This setting can be found on the Image Scaling page. This will help with aliasing in your final output.
Now that all the project settings have been set, we are ready to create a timeline. A good double-check to make sure everything is behaving as expected is to do a little math.
First we take the frame rate or our source divided by our target frame rate.
29.97 ➗ 23.976 = 1.25
This result is our retime factor
Next we use that factor multiplied by the number of frames in our converted timeline.
1.25 * 1445 = 1818.75
That result will be the original # of frames from the 29.97 source. If everything checks out, then it’s time to render.
Rendering
I prefer to render at source resolution and run any upscaling steps downstream. You can totally skip this step by rendering to HD, 4k, or whatever you need.
I would recommend using Davinci’s Super Scale option if you are uprezing at the same time. This option can be accessed via the Clip Attributes... settings in the contextual menu that pops up when you right-click a source clip.
I hope this helps take your dusty old SD video and prepare it for some new life. This is by no means the “best” conversion out there. Alchemist is still my preferred standards conversion platform. Nvidia has also cooked up some amazing open-source tools for manipulating time via its machine vision toolset. All that said, Resolve does an amazing job, besting the highest quality, very expensive hardware from years past. The best part is it’s free.
Happy Grading,
JD