GoPro, full color range and pix_fmt=yuvj420p -- what to hope for and what to avoid?


#1

Dear all,

On a super amateur level, I’m attempting to learn to edit ski videos from a GoPro. I’ve been successful in doing basic editing and exporting satisfactory quality using libx264 to match the original, thanks to Shotcut and the supporting community. Thank you!

In seeking the right export parameters, I noticed a lack of vibrancy in colors in the exported clip. Searching, I found this discussion on the forums, teaching me there might be something about the full range of colors not being exported due to the format of the video being yuvj420p.
The same topic discusses that exporting full range is less than fully operational.

In this topic, I learned that I could add pix_fmt=yuvj420p under Export > Other. My exported test clip then retained vibrancy. Yay!

With this background, I hope it makes sense to ask the following:
– To which degree is adding pix_fmt=yuvj420p a stable/unstable solution? Can I hope that it will work “just work” when I create more elaborate projects?
– The first topic mentions that certain filters will negate the effect – if I am to be sure to retain vibrancy, what should or shouldn’t I do? Can I add text and zoom effects, transitions? What will “break the magic”, so to speak?
– Is this a super newbie and irrelevant thing to worry about, and should I be doing something else entirely?

Kind regards,


#2

pix_fmt=yuvj420p is stable, but you should also add mlt_image_format=rgb24. RGB (in the context of Shotcut and its libraries) are full range. Even though a filter might need to convert to limited MPEG/broadcast range to do its processing, it will expand back to full range in RGB. The result of this operation is some slight degradation due to something called quantization error, but it will largely be negligible. It should not affect the vibrancy you are concerned about, but it is less than ideal; however, so is working in 8-bit. However, much of media processing is about compromise because people do not have the most amount of resources and patience. Here is a list of these filters (assuming GPU Effects is off):

  • Brightness
  • Fade In Video
  • Fade Out Video
  • Hue/Lightness/Saturation
  • Invert
  • Mirror
  • Old Film: Dust
  • Old Film: Grain
  • Old Film: Projector
  • Old Film: Scratches
  • Old Film: Technocolor
  • Opacity
  • Reduce Noise
  • Sepia
  • Sketch
  • Vignette
  • Wave

Intermediate Files for Editing
#3

Thank you very much for this reply. It is highly appreciated!