… for Codecs & Media

Tip #1158: File Size is NOT Image Quality

Larry Jordan – LarryJordan.com

How long is a piece of string? Don’t focus on file size, focus on image quality.

Topic $TipTopic

During a recent webinar, Lane asked:

I’m creating a program of Christmas carols that may run about 30 minutes. I’m concerned about the file size because, when compressed, this program will likely give me a huge file. What should I do to keep file size down?

All too often, editors obsess about the size of their compressed file. This is the wrong thing to worry about.

File size is determined by two factors: bit rate and the duration of the movie. Longer programs will, by definition, have larger file sizes. There’s just more movie than in something shorter.

Instead, we need to focus on image quality. This is a combination of six factors:

  • The codec you are using
  • The frame size of the compressed file
  • The frame rate of the compressed file
  • The amount of movement between frames
  • Whether the movie is for streaming, download or posting to social media
  • The bit rate at which you compressed it

In general, for a 1080p movie, assume a ROUGH compressed file size of 20 MB/running minute. For a UHD file, assuming 60 MB/running minute. Both of these use the H.264 codec, which I recommend instead of HEVC.

These are rough guides, but any longer program is going the create some really large files.


Please rate the helpfulness of this tip.

Click on a star to rate it!

4 Comments
  1. stu aull
    stu aull says:

    Frame RATE too? Hadn’t thought about that! Are we talking diff in size that is significant with, say, a 60FPS vs 24? I would imagine that 95% of vids are either 24 or 30, which would pretty much take it off the table as a way to control final output size?

    Reply
    • Larry Jordan
      Larry Jordan says:

      Rodney:

      Several reasons:
      1. Not all systems support HEVC playback
      2. HEVC takes up to ten times longer to compress
      3. Social media recompresses your files anyway, there’s no reason to waste the time

      HEVC was invented to decrease the amount of data traffic on cellphone networks (i.e to benefit AT&T, Verizon, T-Mobile etc.) For media creators sending files to broadcast, cable, digital cinema or social media, there’s no benefit to using HEVC.

      Plus, it is even harder (i.e. requires faster computers and GPUs) to edit than H.264; which is already hard enough.

      Larry

      Reply

Leave a Comment

Want to join the discussion?
Feel free to contribute!
All comments are moderated.

Leave a Reply

Your email address will not be published. Required fields are marked *