cdr

name	cdr
description	Burn a Sega CD disc image to CD-R so it boots on real Mega-CD / Sega CD hardware. Checks the image is a Sega CD disc, reports its region, verifies the medium is blank and large enough, picks a write speed the medium rates, and writes one Disc-At-Once data track. Use for "CD-Rに焼いて", "実機で動かしたい", "burn the iso", or "/cdr".

cdr: burn a disc image for real hardware

A CD-R is spent on the first attempt, so this skill checks everything it can before writing and refuses anything it cannot justify.

Run every command from the repository root.

What gets burned

make disc CONFIG=profiles/PROFILE.toml DEBUG=0 writes out/PROFILE_release.iso, a Mode1/2048 image with one data track. That is what goes on the disc. The .cue beside it exists for emulators and is not used here: a single-track data disc needs no cue sheet.

Prefer the release disc for real hardware. A DEBUG disc boots equally well but draws the counter row over the picture.

Preconditions

• cdrskin installed (sudo apt install cdrskin). Do not substitute another burner without qualifying it; the SAO behaviour below is what matters.
• A drive that reports Can write CD-R: 1 in /proc/sys/dev/cdrom/info.
• A blank CD-R. The tool refuses a non-blank disc rather than appending a session.

Burn

Report first, then write. The dry run is the default:

tools/python.sh .agents/skills/cdr/scripts/burn_iso.py \
  out/PROFILE_release.iso --expect-region J

It prints the image's Sega CD header, volume name, internal title, size, and region, then the medium's make, rated speed range, and capacity. Read the region line against the console you will use. When it all matches:

tools/python.sh .agents/skills/cdr/scripts/burn_iso.py \
  out/PROFILE_release.iso --expect-region J --burn

Pass --expect-region whenever the target console is known. The image carries a region byte at offset 0x1F0 (J Japan, U North America, E Europe) and a console rejects a disc whose security code is not its own. Catching that mismatch before the write is the difference between a rebuild and a wasted disc.

Why the fixed choices

• Disc-At-Once, single session. Track-At-Once leaves a two-second pregap that an early-1990s Sega CD drive can fail to read past. SAO is not a preference here.
• Speed comes from the medium. The tool clamps any request into the ATIP range the disc reports. Burning below a high-speed dye's rated floor makes the burn worse, not safer, so a lower request is raised to the floor.
• burnfree on. Buffer underrun protection costs nothing on a disc this small.

When real hardware will not boot it

Separate the disc from the data before rebuilding anything:

• A Sega CD's pickup was designed for pressed discs, whose reflectivity is higher than any CD-R. Media brand and dye genuinely change the result on these consoles; a different CD-R can boot where another does not.
• Region is the other common cause. Re-read the region line from the dry run.
• If the burn itself reported a complete track and the drive buffer never starved, the write is not the suspect. Confirm the image boots in the emulator (tools/record_movie.sh --disc out/PROFILE_release.cue --no-build --seconds 30) to prove the data, then treat it as a medium or pickup issue.

Do not claim a disc boots on hardware unless it was actually tried there.