… for Codecs & Media

Tip #099: Benefits of working with 4K in 1080

Larry Jordan – https://LarryJordan.com

4K has benefits aside from increased resolution.

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I was reading Jason Boone‘s blog on the Benefits of Working with 4K Footage in a 1080 Sequence.

First, while it could be argued that we can’t actually SEE 4K in most situations, that hasn’t stopped distributors from requesting it. Still, even if you don’t plan to deliver 4K, there are benefits to shooting it, as Jason outlines:

  • Reframe a shot. 4K provides so many extra pixels to choose from, you can convert a wide shot into a close-up. However, cutting into the frame won’t change depth of field, so the image won’t look the same as if you had zoomed (or dollied) in.
  • Use the same take multiple times. Using the same take for both wide shots and close-ups makes it seem as though you have two cameras. The benefit is that where talent is looking doesn’t change. The disadvantage is that background and depth of field won’t change either.
  • Create camera moves. Using keyframes you can create movement where there was none in the original shot. However, like moves on a still, elements won’t change position as they would if you used a dolly on set.
  • Stabilize your footage. This is powerful. Stabilization always zooms into a shot. By having lots of extra pixels to work with, the image won’t lose detail or sharpness.
  • Adjust the image for graphics. There’s nothing worse than graphics you can’t read. 4K gives us extra pixels for scaling and repositioning.

4K may not be visible to the eye, but it can be a BIG benefit in post.


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… for Codecs & Media

Tip #105: Why Do We Need Intermediate Codecs?

Larry Jordan – https://LarryJordan.com

Intermediate codecs simplify editing.

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An “Intermediate Codec” is a video format that we use for editing. It is placed between the format shot by the camera and the format we need for final distribution. We convert between formats using “transcoding.”

There are two different reasons for using an intermediate codec:

  • To make really large files manageable
  • To make highly-compressed files easier to edit

MANAGEABILITY

For example, we often use proxy files when rough cutting 4K or larger frame sizes, or working with HDR media, simply because these source files are incredibly massive. Using a smaller intermediate codec allows us to successfully work with less storage on slower systems.

HIGHLY-COMPRESSED

Files that are optimized for editing store each image individually in the file (called an “I-frame”.). These include formats such as ProRes, DNx, and Cineform. I-frame compression means that as soon as the playhead lands on an image, it can be displayed.

I-frame files are very efficient for editing, but large.

Highly-compressed files, such as AVCHD, H.264 or HEVC, only record one image every 15 frames or so. The rest of the “images” are actually text descriptions of the changes between the source frame (“I”) and all the derivative frames (“B” and “P”). In order for the computer to display a B or P frame, it needs to go back to the I frame, then apply all those text-based change documents to calculate the frame the playhead is currently parked on.

If you are playing a clip, GOP compression is not a big deal. But, skimming clips, playing backward, jumping randomly around in a file, or multicam editing can take a while to calculate and display these images because the computer always needs to jump back to the nearest earlier I-frame and recalculate.

Transcoding to an intermediate codec means that editing, rendering and exporting will be faster by converting GOP-based encoding into I-frames.