Test a font for being able to render an emoji using ffmpeg

ffmpeg-test-emoji.sh

#!/bin/bash

# Tests out the generation of subtitles using a smiley emoji and the "sparkles" emoji.
# Note that some fonts like sans and sans-serif may have the smiley (0xf09f9884), but not the sparkles (0xe29ca8).
# Some fonts will have neither.
# I think support for emojis in FFMPEG/mpv/fonts could use some improvement.

exec 4>subs.srt
echo "1" >&4
echo "00:00:00.000 --> 00:00:02.000" >&4
echo -e "Now let's see that \xf0\x9f\x98\x84 !!!" >&4
echo -e "\n" >&4
echo "00:00:02.000 --> 00:00:04.000" >&4
echo -e "How about \xe2\x9c\xa8sparkles\xe2\x9c\xa8 ??" >&4
echo -e "\n" >&4
exec 4>&-

font="${1:-sans-serif}"

filter_complex="[0:v]subtitles=subs.srt:force_style='Alignment=0,PrimaryColour=&H00FFFFFF"
filter_complex+=",FontName=${font},OutlineColour=&H40000000,BorderStyle=3,Fontsize=25,MarginV=25'"
filter_complex+=",format=yuv420p[v]"

lavfi="color=0x00000000:size=512x512,fps=25,format=rgba,setsar=1:1"

ffmpeg -hide_banner -v debug -f lavfi -t 4 -i "$lavfi" -i subs.srt \
  -filter_complex "$filter_complex" -map [v] -y subs.mp4