Stitch format PMV

.pmv files are a brother stitch format.

Overview

Stitch formats are strictly embroidery in the traditional sense. They are the applications of patterned stitches on to fabric. But these are done with programs within the sewing machine itself. Rather than the entire XY field of the hoop they have a Y field of the presser foot and an X dimension forward and back along the fabric. It is for this reason that the formatting is stored in a hybrid absolute/relative manner with different encoding schemes. The amount the element moves up in the fabric is different than the amount the needle moves within the presser foot.

There are several other related Brother stitch files this is simply the only one analyzed.

Header

The header is exactly 100 bytes long. 7 bytes of format spec, 36 of copyright. And 57 bytes of a few different stitch settings.

Type	Bytes	Value	Description
`string`	7	"#PMV0001"	Nearly ever brother format starts with a similar header.
`string`	36	copyright	This is not needed for the format explicitly but the files contain a copyright message. This doesn't affect whether the files work or not.
`s8`	9	b'\x01\x00\x00\x00\x00\x00\x00\x00\x00'	Unknown
`s8`	1	Length Offset	Usually 00, but can be set within the stitch and saved. It's the offset from the default in signed 8 bit.
`s8`	1	Width Offset	Usually 00, but can be set within the stitch and saved. It's the offset from the default in signed 8 bit.
`s8`	3	b'\x00\x00\x01'	Unknown
`s8`	14	b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'	Unknown
`s8`	3	b'\x00\x00\x00'	Unknown
`s16`	2	L/R shift	Usually 0, but gives the length offset in left and right directly to the current value.
`s8`	9	b'\x00\x00\x01\x00\x00\x00\x00\x00\x00'	Unknown
`s8`	14	b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\x00\x00'	Unknown

L/R shift is a 16 bit integer located at 0x4A-0x4B. The length table offset is an 8 bit int located at 0x34 and the width table offset is located at 0x35. These can be set within the stitch on the machine and then saved out again saving their value. The table offsets are signed 8 bit numbers, and are added to the default table values located within the tables.

Stitch Block

Point count Byte count. 6 bits forward/back 5 bits movement within presser foot.

While +15,-16 is possible beyond 14,14 is never seen.

Ends with 0, 256 16le 0 16le 256 Likely due to there not being another stitch block.

Followed by 16 bytes of unknown. b'\x00\x00\x00\x00\x05\x00\x00\x00' b'\x00\x00\x00\x00\x00\x00\x02\x00'

Control Tables

Unknown: 16le 256 8 0 8 0

The sewing machines apparently don't do the math themselves so they process a bunch of tables of settings.

   length_range = max_x - min_x
   write_length_lookup_table(f, length_range)
   width_range = max_y - min_y
   write_width_lookup_table(f, width_range)
   write_int_16le(f, 0x12)
   f.write(b'\x00\x00\x00\x00\x00\x00\x00\x00'
           b'\x00\x00\x00\x00\x00\x00\x00\x00')

Length Lookup Table

Since the length travelled is independent from the width within the presser foot. These are often very similar. For the satin stitches they often have 1 value that turns them off. For most of the dynamic stitches they are quite similar and fit into a semi-log curve but this is mostly to ensure they have finer details at the low end.

Default value here would be position 12 within the table.

Table Count.

Type	Bytes	Value	Description
`s8`	1	Typically: 12	The default position within the table.
`s8`	1	N - Number of table entries.	Gives the table count before the table.
`s16`	4 * N	Table Entries	The table elements.

Type	Bytes	Value	Description
`s16`	2	value 1	Dunno specifically.
`s16`	2	value 2	Dunno specifically.

Position	Value 1	Value 2
0	0	0
1	10	71
2	20	143
3	40	214
4	60	286
5	80	357
6	100	429
7	120	500
8	140	571
9	160	714
10	180	786
11	200	857
12	250	1000
13	300	1286
14	350	1429
15	400	1571
16	450	1786
17	500	2000

Width Lookup Table

   pos = int(width_range / 2)
   write_int_8(f, pos)
   if width_range == 0:
       write_int_8(f, 1)
       write_int_16le(f, 8192)
       write_int_16le(f, 1000)
       return
   steps = 15
   write_int_8(f, steps)
   second_max = other_step = 28000.0 / float(width_range)
   second_step = second_max / float(steps - 1)
   for i in range(0, steps):
       width_at_step = 50 * i
       other_at_step = second_step * i

       write_int_16le(f, width_at_step)
       write_int_16le(f, int(round(other_at_step)))