Simplified method of remuxing MKV with Dolby Vision P7 FEL to P8.1 with EL discarded

FEL2P8.sh

#!/bin/bash

if [ "$#" -ne 1 ]; then
  echo "Usage: $0 input_file" >&2
  exit 1
fi

input_file="$1"
input_dir=$(dirname "$input_file")
input_base=$(basename "${input_file%.*}")

# Extract and convert the BL+EL to BL only
ffmpeg -v quiet -stats -i "$input_file" -c:v copy -vbsf hevc_mp4toannexb -f hevc - | dovi_tool -m 2 convert --discard -i - -o "$input_dir/BL_RPU.hevc"

# Merge new HEVC and all non-video tracks from the original MKV
mkvmerge -o "$input_dir/$input_base.P8.mkv" \
  "$input_dir/BL_RPU.hevc" \
  --compression -1:none \
  -d !0 \
  "$input_file"

# Delete BL file from earlier
rm "$input_dir/BL_RPU.hevc"