erikandClaude Opus 5.5
e1c1012c1c
UVC extension-unit control (mouse/scan mode, LEDs, exposure), JPEG header fix and embedded laser record decoding, session recorder, and a stitcher that combines laser dead reckoning with phase correlation and ECC refinement. FINDINGS.md holds the reverse-engineered protocol and laser calibration. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
81 lines
2.7 KiB
Python
81 lines
2.7 KiB
Python
"""Decode Hama myScan / Dacuda scanner-mouse MJPEG frames.
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The firmware hides a per-frame sensor record in the JPEG headers (reverse
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engineered from OVJpegSrcPreProc / DaReadMouseData in Omnivision's
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UVCControl.framework shipped with the Dacuda Scanner Mouse Mac app):
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* SOF0 height/width bytes carry 4 data bytes; the true size is 640x296.
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* Entries 0x36..0x44 (relative to the FF marker) of the second DQT carry
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15 more data bytes; the true table value there is 0x19.
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"""
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import struct
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from dataclasses import dataclass
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WIDTH, HEIGHT = 640, 296
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def _spcal(v, mode, bit):
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# OVSPCal: undo the encoding that keeps quant-table bytes legal.
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if mode == 2:
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r = max(v - 1, 0) * 4 + 2
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elif mode == 3:
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r = max(v - 1, 0) * 4 + 3
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elif mode == 1:
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r = v * 4 + 1
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else:
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r = v * 4
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return ((r & 0xFB) | ((bit & 1) << 2)) & 0xFF
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@dataclass
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class SensorRecord:
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counter: int
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v: tuple # six big-endian 16-bit values; [2] and [5] are not transmitted
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b14: int
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b15: int
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b16: int
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flags: int # five flag bits (byte 17)
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raw: bytes
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def fix_and_extract(jpeg: bytes):
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"""Return (clean_jpeg, SensorRecord | None)."""
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buf = bytearray(jpeg)
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s = bytearray(32)
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have = 0
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dqt = 0
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i = 0
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n = min(len(buf), 40000)
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while i < n - 1:
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if buf[i] == 0xFF:
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m = buf[i + 1]
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if m == 0xD8:
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have |= 1
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elif m == 0xC0:
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have |= 2
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s[0], s[0x14], s[0x15], s[0x16] = buf[i + 5:i + 9]
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buf[i + 5:i + 9] = struct.pack('>HH', HEIGHT, WIDTH)
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elif m == 0xDB:
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dqt += 1
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if dqt == 2:
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have |= 4
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d = buf[i + 0x36:i + 0x45]
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for dst, src in zip((0x18, 0x19, 0x1A, 2, 3, 4, 5, 8, 9, 10, 11, 14, 15, 16, 17), d):
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s[dst] = src
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buf[i + 0x36:i + 0x45] = b'\x19' * 15
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if have == 7:
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break
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i += 1
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if have != 7:
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return bytes(buf), None
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# Each data byte gets a 2-bit mode from bytes 0x14..0x16 and one bit from 0x18..0x1a.
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plan = [(2, 0x14, 6, 0x18, 5), (3, 0x14, 4, 0x18, 4), (4, 0x14, 2, 0x18, 3), (5, 0x14, 0, 0x18, 2),
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(8, 0x15, 6, 0x18, 1), (9, 0x15, 4, 0x19, 5), (10, 0x15, 2, 0x19, 4), (11, 0x15, 0, 0x19, 3),
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(14, 0x16, 6, 0x19, 2), (15, 0x16, 4, 0x19, 1), (16, 0x16, 2, 0x1A, 5), (17, 0x16, 0, 0x1A, 4)]
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for dst, mreg, msh, breg, bsh in plan:
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s[dst] = _spcal(s[dst], (s[mreg] >> msh) & 3, s[breg] >> bsh)
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vals = tuple((s[2 * k + 2] << 8) | s[2 * k + 3] for k in range(6))
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rec = SensorRecord(s[0], vals, s[14], s[15], s[16], s[17] & 0x1F, bytes(s[:20]))
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return bytes(buf), rec
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