Fontconfig error when using drawtext filter

[danielroehrig]

When trying to add text to a video on Linux-64 (Ubuntu 19.10), this error appears:

ffmpeg stderr: Fontconfig warning: line 5: unknown element "its:rules"

The text is still written, but it takes about a minute per second of video material.

When replacing the ffmpeg binary with a newer one (git master: built on 20200324) from https://www.johnvansickle.com/ffmpeg/ the error disappears and the video is rendered in seconds.