JEF

Status

What it is

JEF is the common machine format for Janome home embroidery machines. Unlike sparse expanded streams, it usually carries hoop, palette, extent, and stitch-offset information.

Satin Studio behavior

Satin Studio imports exact JEF stitches with their hoop and thread metadata. Export stops when the selected Janome machine or hoop cannot safely contain the design.

Versions and variants

Version letters, hoop codes, palette tables, trim settings, and JEF+ variants differ by machine generation. Satin Studio identifies the target generation before applying those records.

File identification notes

JEF is little-endian and header-driven. Publicly documented fields include:

• A stitch-data offset, commonly 0x74 + 8 * color_change_count.
• A date/version area, including version letters used by different Janome machine generations.
• Color count and point/stitch-data length fields.
• Hoop code and extent/edge-distance records for common hoops.
• A palette-index list and repeated separator values before the stitch data.

The stitch body uses signed 8-bit relative x, y movement. If x == 0x80, the record is a command. Common command prefixes are:

• 0x80 0x10: end.
• 0x80 0x01: color change / stop.
• 0x80 0x02: jump; also used as trim behavior in some machine/software settings.

Some Janome machines can trim on color changes, long jumps, or explicit zero-distance jump/cut commands depending on machine settings.

Observed structure notes

• Observed JEF readers start with a little-endian stitch-data offset, skip date/version-style metadata, read a color count, then read palette indexes before seeking to the stitch stream.
• Normal stitch records are signed two-byte dx, dy pairs with Y inverted for embroidery coordinates. A first byte 0x80 introduces a command byte plus two payload bytes.
• Observed commands include 0x02 jump with payload movement, 0x01 color change or stop depending on the next thread entry, and 0x10 end.
• Observed writers compute stitch-data offset as 0x74 + color_count * 8 and then write palette indexes followed by repeated 0x0D separator values before stitch data.
• Observed JEF headers include a 14-byte timestamp string, color count, point count, hoop code, design half-width/half-height, and edge distances for common hoops.
• Observed writers finish stitch data with 0x80 0x10 and no movement payload.

Structure sketch

JEF is little-endian and header-driven. Stitch data starts at the offset stored in the header.

struct JefFile<'a> {
    stitch_data_offset: u32,
    header_after_offset: &'a [u8],      // date/version, counts, hoop, extents, and separators vary by generation
    palette_indexes: &'a [u32],
    stitch_records: &'a [JefRecord],
}

enum JefRecord {
    Stitch { dx: i8, dy: i8 },
    Jump { dx: i8, dy: i8 },            // 0x80 0x02 + payload movement
    ColorChangeOrStop,                 // 0x80 0x01
    End,                               // 0x80 0x10
}

Compatibility evidence

Compatibility checks cover signatures, metadata, command boundaries, malformed records, and files from the machines and software named above. Unsupported variants stop with a specific report instead of being silently rewritten.