CMv4.0 to CMv2.9 conversion support

[dzuelke]

I remember you mentioning wanting to look into CMv2.9 conversion (on Reddit maybe?). Apple TV 4K generations 1 and 2 only support Content Mapping version 2.9. It's possible to convert between these two formats.

I currently use a script to do find any such files like so (this one finds profile 7 files and any files with CMv4.0):

#!/usr/bin/env bash
# Apple TV cannot play DV Profile 7, or any DV Profile that uses Content Mapping v4.0 (https://professionalsupport.dolby.com/s/article/When-should-I-use-CM-v2-9-or-CM-v4-0-and-can-I-convert-between-them)
for f in "$@"; do
	codec=$(
		ffprobe -loglevel error -i "$f" -select_streams v:0 -show_entries stream=codec_name -of default=nokey=1:noprint_wrappers=1
	)
	if [[ $codec == "hevc" ]]; then
		echo -ne "\033[1K\r$f"
		reason=$(
			dovi_tool info -f0 <(
				ffmpeg -loglevel error -i "$f" -c:v copy -frames:v 1 -bsf:v hevc_mp4toannexb -f hevc - \
				| dovi_tool extract-rpu - -o /dev/stdout
			) 2>/dev/null \
			| tail -n +2 \
			| jq -re '(.dovi_profile | select(.==7) | "DV7") // (.vdr_dm_data.cmv40_metadata | select(.!=null) | "CMv40")'
		) && {
			echo " is $reason"
		}
	fi
done

https://github.com/nekno/DV7toDV8 then can do the conversion (although IMO you should lift the fairly simple logic out of there and port it to your Python script, instead of relying on it as a dependency).

[cryptochrome]

I still have this in my to do list, so thank you! This is helpful.