A UDPS_TIME_FIRST_SAMPLE time signal carries one meaningful value -- the
batch's first sample -- but a scalar signal in Accumulate mode still occupies
num_samples slots on the wire, which a producer fills by repeating that
anchor. Deriving the step from value_of(n - 1) therefore came out as zero, so
every sample of a frame landed on one x, the degeneracy guard tripped, and the
whole stream was timed by packet arrival instead. On a 1 MS/s source that
arrival clock is not monotonic within a frame: the export's time column held
90559 order breaks.
Space the batch by the cadence, exactly as the LAST_SAMPLE branch beside it
already dates its own batch backwards. The export's time column is now
strictly increasing (0 duplicates, 0 backwards steps) and reads the declared
1 MS/s.
mock_udpstreamer gains --time-mode {full,first}; it could only emit
FULL_ARRAY, so nothing exercised this branch. In 'first' it repeats the anchor
across the batch's wire slots -- the shape that produced the defect -- while
still generating the waveforms from the real per-sample stamps.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
