A multi-angle scan runs for hours, but every angle was referenced against
one background captured before the first row of the first angle. That
reference has drifted by the last angle, and comparing angles — the whole
point of a multi-angle scan — was comparing each one against a noise floor
measured at whichever angle came first.
Every angle now captures its own. Before each angle's rows, the operator is
prompted to switch the Genesis laser off, the engine averages a fresh CH1
record, and the operator switches it back on. The data block therefore reads
[background][scan][background][scan] …, one pair per angle.
Format v7 (scan) and v11 (SAW check) carry the background inside the data
block, one length-prefixed block ahead of each angle's rows; the single
block that sat between the preambles and the data is gone. Per-angle offsets
now come from a walk of the data block at parse time rather than arithmetic
over the geometry table, and an angle whose background is not fully on disk
is the frontier — nothing of it was written yet.
v6/v10 files still read: SrasFile hands their one background to every angle,
so readers never branch on the version. Nothing writes them, and a resume
refuses them, since a re-acquired angle writes a block the old layout has no
room for. A resumed v7 angle rewrites its background in place, and the
engine checks the new block fits the room the file has before writing it —
anything else would shift every row behind it.
Two fixes made along the way:
* QtScanController never accepted file_version, so every scan launched
from the app raised TypeError at construction.
* angle_status() left its cursor parked at the frontier, so every angle
past it reported the frontier's own data_offset — which handed a resumed
scan the same write position for several angles. Two recorded offsets in
tests/golden/sras_expected.json are corrected accordingly.
The v6 goldens stay as parser fixtures; the writer is now locked against
bytes the test lays out from scan_format.md itself.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A full multi-angle scan takes hours, and a rig whose angles disagree produces
all of them before anyone finds out. This adds a test mode that acquires one
row per angle — the row-wise middle of the ROI — and a viewer that puts every
angle's SAW frequency on one graph. The default 80×50 mm ROI at 5 angles goes
from 1461 rows to 5.
Why the middle row answers an alignment question at all: build_plan centres
every angle's rotated bounding box on the same nominal ROI centre, so each
angle's middle row crosses that one point on the sample. All the angles
measure the same material, so a spread in their frequencies belongs to the rig
rather than to where each row happened to land. test_every_angles_middle_row_
crosses_the_roi_centre pins that premise, since the whole comparison rests on
it and nothing else in the geometry code would notice it breaking.
core/saw_check.py — both halves of the mode, kept together because neither is
much use alone. middle_row_plan() reduces a ScanPlan to one row per angle
(n_rows // 2, the upper of two centre rows when even); frequency_traces() and
alignment_summary() turn the resulting file back into per-angle frequency
traces and the scalars an operator is actually asking about — the spread of
the per-angle medians, the worst drift along a row, the sparsest row. The
verdict thresholds are labelled as rules of thumb, not physics: an anisotropic
sample genuinely varies with angle, so a wide spread is a prompt to look at
the curves rather than a verdict.
Format v10: byte-identical to v6, one row per angle. The version byte earns
its keep because the two are otherwise indistinguishable — a v6 scan aborted
after its first row is not a check, and a reader guessing from the row count
would read a failed scan as a deliberate measurement. create_scan_file()
enforces the one-row rule at write time, since nothing downstream can recover
from a v10 file that breaks it. ScanEngine gains file_version and is otherwise
untouched: the acquisition, the abort/pause path and the background capture
are the scan's, unchanged.
sras_scan_manager.py now carries the source file's version through an export
instead of stamping v6 on everything, which the wider reader would otherwise
have made a lie.
saw_check_viewer.py — frequency along the row, one curve per angle, over a
common offset axis so the curves lie on the same piece of sample; a summary of
each angle's median ±1σ against angle; and the per-angle numbers in a table.
Analysis parameters (DC threshold, background, time gate) recompute on a
worker thread; display ones (smoothing, axis, MHz↔m/s) only redraw. A full v6
scan opens too — the same middle row is pulled out of it — so a finished scan
can be re-examined with the check's own read-out.
In the app, a check finishes by handing the operator the file and an "Open
Viewer" button rather than shutting the rig down the way a completed scan
does. Burst mode is not offered: one row per angle means every burst would be
a single row, so it buys nothing and still pays for the gate preflight.
137 tests passing, ruff clean.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
A mis-triggered row cannot be written as it arrived — v6 declares n_frames per
row in the header and has no per-row length field, so a short or long row
would shift every later row in the file. Until now the only policy was to
square it up, which keeps the scan running but leaves the affected row
indistinguishable from a good one afterwards: nothing in the file records that
it was padded.
strict_rows selects the other trade. On any frame-count mismatch the scan
stops instead of writing the row, so a data run either produces rows that mean
what the header says they mean or fails loudly. Default stays pad, so existing
behaviour is unchanged.
_warn_frame_delta becomes _check_frame_delta, since it now decides rather than
just reports. Both acquisition paths already call it before writing anything
for the row (CH1 leads SCAN_CHANNELS, and the burst path checks every row up
front), so an abort leaves the file on a whole-row boundary rather than a
half-written row — test_strict_row_packing_writes_nothing_for_the_failed_row
pins that.
Plumbed through QtScanController to a checkbox in the scan panel, persisted in
ScanDefaults alongside burst_mode. scan_format.md documents both policies and
notes that the choice is not recorded in the file.
The row-clipping setup in the padding test is now a _clip_one_row helper,
reused by the strict tests. 92 tests passing, ruff clean.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Wires the burst_mode flag through QtScanController to ScanEngine and adds a
checkbox to the scan panel. The setting persists via ScanDefaults like the
other scan fields, defaulting to off — per-row acquisition stays the default
path until burst mode has run on the rig and the gate-off preflight has
settled which TRIGOUT value idles the pin low.
scan_format.md — the acquisition settings table had drifted from the code it
claimed to describe: it attributed the settings to sc3_aui_app.py (they moved
to core/scope_sras.py in the Phase 2 extraction), listed a 1.24 V trigger
level and 0 % offset where the code sets 0.500 V and HORizontal:POSition 30,
and did not mention the logic-AND scan trigger at all. Corrected, pointed at
the module that actually owns them, and noted that none of it affects byte
layout — only where the acoustic packet lands inside a frame.
Added an acquisition-paths section: the two paths write byte-identical files
and the choice is a runtime flag that is not recorded in the file, so a
reader never needs to care which produced it. Documents where row boundaries
come from in a burst and that either path squares rows up to n_frames.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Thomas Ales