29926851: iMovie/Final Cut Pro X: Red tinted video when using bt601 color matrix

[openradar-mirror]

Description

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.

- Product Version: iMovie 10.1.4 on macOS 10.12.2 Created: 2017-01-09T14:43:31.702090 Originated: 2017-01-09T15:30:00 Open Radar Link: http://www.openradar.me/29926851

[openradar-mirror]

Modified: 2017-05-07T17:19:07.224690

[openradar-mirror]

Modified: 2017-05-07T17:19:07.224690

[openradar-mirror]

Modified: 2017-05-07T17:19:07.224690

[openradar-mirror]

Modified: 2017-05-07T17:19:07.224690

[openradar-mirror]

Modified: 2017-05-07T17:19:07.224690

[openradar-mirror]

Modified: 2017-05-07T17:19:07.224690