iMovie/Final Cut Pro X: Red tinted video when using bt601 color matrix

Originator:jvmscholz
Number:rdar://29926851 Date Originated:09-Jan-2017 03:30 PM
Status:Open Resolved:
Product:iLife Product Version:iMovie 10.1.4 on macOS 10.12.2
Classification:Serious Reproducible:Always
 
Summary:
I bought myself a cheap china action cam and discovered that the video looks fine in Quicktime and quicklook. But as soon as I imported the video into iMovie, it was completely red tinted. A short search on youtube brought up that this is a problem known back to 2013.

I digged around a little bit and was able to nail it down to being a problem color matrix codes. My camera records mp4 (don't ask me why, ugh) with a BT.601 color code (although the video can be in HD...). What I discovered is that when I convert this to BT.709 with ffmpeg, the red tint is gone in iMovie.

I consider this to be a serious bug as the scope of this bug is iMovie/Final Cut Pro X and is not easy to discover and workarounds involve retranscoding which is generally not wanted before editing.

Steps to Reproduce:
1. Import the first attached file. It will appear red tinted in iMovie in the preview window on the right side
2. Import the attached file with the suffix "color_matrix_converted" (this file is in BT.709). This file will not be red tinted.

I used ffmpeg (easiest installation with homebrew or macports) with the following command to convert the first file:

ffmpeg -i pathToFile/20170101_000126A.mp4 -vf colormatrix=bt601:bt709 pathToFile/20170101_000126A_colormatrix_corrected.mp4 


Expected Results:
I'd expect iMovie to handle files with bt.601 encoding fine, especially as Quicktime and quicklook already do.

Actual Results:
red tinted video in the case of bt.601 video under special circumstances.

Version:
iMovie 10.1.4 on macOS 10.12.2

Notes:
A workaround suggested on youtube is to use converters that convert the video in some other format.

I poked it with a stick, and the most helpful stick was mediainfo.

Configuration:


Attachments:
'20170101_000126A.mp4' and '20170101_000126A_colormatrix_corrected.mp4' were successfully uploaded.

Comments


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