M8Tape

Multichannel recorder for the Dirtywave M8 on the TrimUI Brick (NextUI / MinUI).

M8Tape captures the M8's 24-channel USB audio output and splits each take into 12 stereo files, ready to mix. Capture format: 24 channels, S24_3LE (packed 24-bit), 44100 Hz.

Output

One timestamped folder per take:

M8Tape.pak/rec_YYYYMMDD_HHMMSS/
  01.wav   (channels 1+2)
  02.wav   (channels 3+4)
  ...
  12.wav   (channels 23+24)

Pair N contains channels 2N-1 and 2N. The raw 24-channel WAV is removed after a successful split.

Requirements

• TrimUI Brick running NextUI (or a tg5040-compatible MinUI).
• Dirtywave M8 with USB audio output enabled.
• USB-C data cable, connected to the Brick's top USB-C port.
• A fast microSD card (V30 or better) recommended for direct recording.

Installation

1. Copy the M8Tape.pak folder into Tools/tg5040/ on the SD card.

2. Place the two tg5040 binaries in M8Tape.pak/bin/tg5040/ (see bin/tg5040/PLACE_BINARIES_HERE.txt):

   Binary	Purpose	Source
   minui-list	native menu	josegonzalez/minui-list releases, tg5040 asset
   m8split	24ch → 12 stereo split	build from source — see m8split-src/BUILD.md

   These binaries are not committed to the repository. m8split is built from the included C source with a single zig command (see below). That's all — nothing needs to be typed on the Brick. The pak sets the executable bit on launch.sh and the binaries itself at each launch (FAT32 / exFAT cards do not store permissions).

Usage

1. Connect the M8 (top USB-C port, data cable, USB audio enabled).
2. Open Tools > M8Tape.
3. Start begins the take; the menu then shows Stop, the start time, and the current folder.
4. Stop ends the recording: arecord finalizes the WAV header, then the split produces the twelve stereo files.

The recording may be left running when leaving the menu, and stopped on a later visit.

How it works

• USB capture via arecord at the fixed 24ch / S24_3LE / 44.1 kHz format.
• USB stability: snd_usb_audio.nrpacks=1, USB autosuspend disabled, and device power control forced on for the duration of the take.
• Scheduling: elevated process priority (nice -n -19) and large arecord buffers.
• Split: via m8split if present, otherwise sox; if neither is available, the raw 24-channel WAV is kept intact. m8split is a small static binary built from m8split-src/ — see its BUILD.md.

Recording modes

• Direct (default): writes straight to the card, no duration limit.
• RAM (fallback for slow cards): create an empty file named use_ram in M8Tape.pak/ to record into memory and copy to the card on stop. This removes glitches on slow cards but limits take length to available RAM (~3 min on the Brick). Delete use_ram to return to direct mode.

Desktop splitting (split_m8.sh)

If a take comes back from the device as a raw 24-channel WAV (no splitter was available on the Brick), split it on a computer with split_m8.sh. It requires no compilation and uses ffmpeg or sox, whichever is installed.

chmod +x split_m8.sh
./split_m8.sh take_24ch.wav [output_dir]

Output defaults to a <name>_stems/ folder next to the input, containing 01.wav … 12.wav (same pairing as on-device).

Fallbacks and troubleshooting

Situation	Behavior
No minui-list	Toggle mode (first launch starts, next stops); no menu.
No m8split	sox is used if present; otherwise the raw 24ch WAV is kept.
arecord missing	Status written to state/status.txt; nothing is recorded.
Issue during a take	See state/status.txt and state/arecord.log.

Limitations

• FAT32: the raw take is capped at 4 GB (~21 min) before split. exFAT has no limit.
• RAM mode: take length bounded by available RAM (~3 min on the Brick).

Status

The full pipeline (per-take folder, capture, 12-stereo split, raw cleanup) has been simulated and verified off-device, and the m8split logic tested on real 24-channel WAVs. Real arecord capture and minui-list rendering remain to be confirmed on the Brick.

Repository layout

M8Tape.pak/
  launch.sh   capture, USB tuning, split, fallbacks
  pak.json    NextUI label
  README.md   on-device copy of this document
  bin/tg5040/ place minui-list and m8split here (not committed)
m8split-src/  m8split C source, build script and BUILD.md
split_m8.sh   desktop splitter (ffmpeg/sox)