… for Codecs & Media

Tip #903: A Caution About Frame Rate Conversions

Larry Jordan – LarryJordan.com

The highest image quality occurs when media is played at its source frame rate.

Topic $TipTopic

During this last week, I’ve gotten more emails than usual about frame rate conversions. Some of the concerns are software related; for example, there may be a problem with Compressor converting 24 fps material to 25 fps.

However, the bulk of my email centered on jitter caused by the conversion.

It is important to stress two key points:

  1. The web does not care about the frame rate of your media. The web plays anything. There’s no benefit to changing rates.
  2. The best image quality is ALWAYS when media is played back at the frame rate it was shot. As much as possible, shoot the frame rate you need to deliver.

Converting from 24 to 48, 59.94 to 29.97 or 60 to 30 is smooth and easy; every other frame is dropped or each frame is doubled. But converting 24 to 25, or 30 to 25 or 29.97 to 24 is a recipe for stutter and jitter.

To decrease your stress, before you start shooting, carefully think about the frame rate you need to deliver – or potentially might need to deliver – then shoot that rate. (And, remember, again, that the web doesn’t care about frame rates. So don’t convert media for the web.)


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4 Comments
  1. Richard Malcolm
    Richard Malcolm says:

    I work for a Music Conservatory and we are all off campus at this point. I am getting projects where between 8-50 students send me their video of themselves playing their part of an orchestra work, etc.

    As you can imagine, they are shooting with their devices and I am getting every possible frame rate, resolution, codec, format etc that you can imagine. – and some that you can’t imagine!

    How would you approach working with so many different types of files? We are using Premiere Pro.

    Thanks as always for all you do for the community!

    Reply
    • Larry Jordan
      Larry Jordan says:

      Richard:

      First and most important, I would convert all of the movies to the same frame size, frame rate and orientation (horizontal or vertical). Premiere now fully supports Apple ProRes for both Windows and Mac systems, I would convert to that.

      Then, as you build your sequences, convert to a proxy workflow. This will allow you to successfully stream all these different videos without breaking your system.

      Larry

      Reply
  2. David vogt
    David vogt says:

    There are additional frame rate ratios that yield perfectly clean translations. For a given input frame rate, all that is required is a ratio or % that causes the conversion to always select one where both are integer frame numbers. A few minutes with a spread sheet will show them. All the suggested percentages in the FCPX speed control work, and there are additional ones as well for specific input frame rates.

    Reply

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