.m3u files: handling multi-disc games properly

You copy Final Fantasy VII to your microSD card, and the console shows three entries: Disc 1, Disc 2, Disc 3. Three thumbnails for a single game. The real problem comes when the game asks for the next disc: you have to quit, go back to the list, launch the right file and hope your save follows. On a handheld you switch on for twenty minutes on the train, that routine kills the fun.

The .m3u file solves both issues at once: it groups the discs under a single entry and lets you swap discs without leaving the game. Five minutes per title, once and for all.

An m3u is just text

No special tool is required. An .m3u contains the list of the game's discs, one file name per line, in order. The emulator reads it, understands it is dealing with a multi-volume game and enables a disc-swapping mechanism. The RetroArch documentation sums up the procedure: a text file in the same folder as the content, the full name of each disc, extension included, one per line.

The method, step by step

1. Put all the game's discs in the same folder.
2. Create a text file in that folder.
3. Write one line per disc, exact name and extension included.
4. Save, then rename the file to .m3u.

For a BIN/CUE game, list only the .cue files: they describe the tracks, and the .bin files follow on their own. For CHD files, list the .chd files. Typical content of a file named Final Fantasy VII (France).m3u:

• Final Fantasy VII (France) (Disc 1).chd
• Final Fantasy VII (France) (Disc 2).chd
• Final Fantasy VII (France) (Disc 3).chd

Nothing else: no title, no comment, no extra blank line. The order sets the numbering, with the first line being disc 1. And write only the file name, never a path like C:\Games\PS1\...: it exists on your PC, not on the console.

The .txt extension trap

This is mistake number one, and it is invisible: the editor saves game.m3u.txt, the console sees nothing, and you go looking for a complicated cause.

On Windows, Notepad adds .txt by default: in the save dialog, switch the type to All files before typing the full name. Also turn on extensions in File Explorer, otherwise you will not see a thing. Microsoft gives the path: View > Show > File name extensions.

On macOS, TextEdit works in rich text unless told otherwise: go through Format > Make Plain Text, otherwise the file you get is a disguised RTF. The save window then offers to add .txt automatically; untick that option. Finally, turn on extensions in the Finder settings, Advanced tab.

Naming: a shared base

The rule fits in one sentence: the m3u carries the game's name, the discs that same name followed by their number. Metal Gear Solid (France).m3u on one side, Metal Gear Solid (France) (Disc 1).cue and (Disc 2).cue on the other.

This is not fussiness: that shared base determines whether cover-art scrapers recognise the title, and the name of the save file. Cataloguing conventions already put the (Disc n) in that spot. For the destination folder, our guide to the file structure details what muOS, KNULLI and stock firmwares expect.

Swapping discs without leaving the game

This is the real benefit. The game asks for disc 2, you open the emulator menu and swap on the fly. In RetroArch, the quick menu has a Disc Control entry. The procedure described by the emulation cores is always the same: eject the disc (Eject Disc), set the current disc index (Current Disc Index) to the number you want, then reinsert (Insert Disc). The game picks up where it left off. The same menu offers Load New Disc and Disc Image Append.

A few games need a workaround. Metal Gear Solid only registers the ejection if you leave the menu with the index set to "no disc" before coming back to insert the next one: when a swap fails, it is almost always because the game did not have time to notice the drive was empty. Our essential RetroArch settings explain how to assign the button that opens this menu.

Saves follow the loaded file

Here is what people find out too late. A PlayStation emulator names its memory card after the loaded content: the Beetle PSX core documentation illustrates this with Final Fantasy VII (USA).m3u and Final Fantasy VII (USA).srm.

When you launch the m3u, the three discs therefore share a single memory card. When you launch them one by one, you get three separate cards, and your disc 1 save cannot be found from disc 2.

When the m3u is pointless, or does not work

• Cartridges and PSP. A Super Nintendo game or a UMD fits in a single file: nothing to group.
• Standalone Android emulators. DuckStation advertises merging multi-disc games in its list, shared memory cards included: it relies on its database, without an m3u.
• Interfaces that do not display .m3u files. Some firmwares do not associate the extension with the system: the file exists but stays invisible. A recent custom firmware usually fixes this.
• Discs still visible next to the m3u. The m3u adds an entry, it does not remove any: you need to move the discs into a subfolder or hide them from the game list.

If the m3u launches but the game refuses to start, the problem lies elsewhere: BIOS, format, worn-out card. Our fourteen reasons a game will not launch cover it all.

Which systems are affected

PlayStation 1 is the everyday case: our PS1 emulators on handheld consoles detail the cores available for each chip. Half an hour is enough to process an entire library: multi-volume games can be counted on the fingers of one hand. For the machine to go with it, our selection of retro handheld consoles specifies the condition of each model on delivery.