fix

rfg_adc_plotter/cli.py

@@ -40,10 +40,11 @@ def build_parser() -> argparse.ArgumentParser:
     parser.add_argument(
         "--bscan-db-range",
         dest="bscan_db_range",
-        default="80,150",
+        default="auto",
         help=(
             "Фиксированный диапазон цветовой шкалы B-scan в дБ (min,max). "
-            "Напр. 80,150. Применяется к обычному виду (без вычитания фона)."
+            "Напр. 80,150. 'auto' — подобрать один раз по первому кадру. "
+            "Применяется к обычному виду (без вычитания фона)."
         ),
     )
     parser.add_argument("--title", default="ADC Sweeps", help="Заголовок окна")

rfg_adc_plotter/gui/pyqtgraph_backend.py

@@ -827,17 +827,29 @@ def _db_to_linear_amplitude(values: np.ndarray) -> np.ndarray:
     return np.maximum(out, 0.0).astype(np.float32, copy=False)
 
 
+def try_parse_bscan_db_range(spec: Optional[str]) -> Optional[Tuple[float, float]]:
+    """Parse an explicit B-scan dB window 'min,max'. Returns None if not explicit.
+
+    'auto' (or empty/invalid) returns None, meaning "seed once from the first frame".
+    """
+    if not spec:
+        return None
+    if str(spec).strip().lower() == "auto":
+        return None
+    try:
+        p0, p1 = str(spec).strip().replace(";", ",").split(",")
+        lo, hi = float(p0), float(p1)
+        if np.isfinite(lo) and np.isfinite(hi) and lo < hi:
+            return (lo, hi)
+    except Exception:
+        pass
+    return None
+
+
 def parse_bscan_db_range(spec: Optional[str]) -> Tuple[float, float]:
     """Parse a fixed B-scan dB color window 'min,max'. Falls back to the default."""
-    if spec:
+    parsed = try_parse_bscan_db_range(spec)
-        try:
+    return parsed if parsed is not None else BSCAN_DB_RANGE_DEFAULT
-            p0, p1 = str(spec).strip().replace(";", ",").split(",")
-            lo, hi = float(p0), float(p1)
-            if np.isfinite(lo) and np.isfinite(hi) and lo < hi:
-                return (lo, hi)
-        except Exception:
-            pass
-    return BSCAN_DB_RANGE_DEFAULT
 
 
 def compute_background_subtracted_bscan_levels(
@@ -922,7 +934,10 @@ def run_pyqtgraph(args) -> None:
     fft_bins = FFT_LEN // 2 + 1
     spec_clip = parse_spec_clip(getattr(args, "spec_clip", None))
     spec_mean_sec = float(getattr(args, "spec_mean_sec", 0.0))
-    bscan_db_vmin, bscan_db_vmax = parse_bscan_db_range(getattr(args, "bscan_db_range", None))
+    bscan_db_explicit_range = try_parse_bscan_db_range(getattr(args, "bscan_db_range", None))
+    bscan_db_vmin, bscan_db_vmax = (
+        bscan_db_explicit_range if bscan_db_explicit_range is not None else BSCAN_DB_RANGE_DEFAULT
+    )
     runtime = RuntimeState(
         ring=RingBuffer(max_sweeps),
         range_min_ghz=float(SWEEP_FREQ_MIN_GHZ),
@@ -1389,6 +1404,10 @@ def run_pyqtgraph(args) -> None:
     # Fixed manual dB color window for the normal (no-background) B-scan view.
     # Never recomputed per frame; only changed by the user via the spin boxes.
     bscan_manual_levels: Dict[str, float] = {"vmin": bscan_db_vmin, "vmax": bscan_db_vmax}
+    # Seed the manual window once from the first real frame (unless the user set an
+    # explicit --bscan-db-range) so the signal is visible out of the box; it stays
+    # fixed/manual afterwards.
+    bscan_levels_seeded: Dict[str, bool] = {"done": bscan_db_explicit_range is not None}
     # Frozen levels for the background-subtracted residual view (different scale):
     # computed once when background is active, held until a reset event clears it.
     bscan_bg_levels_frozen: Dict[str, Optional[Tuple[float, float]]] = {"held": None}
@@ -2137,8 +2156,13 @@ def run_pyqtgraph(args) -> None:
             runtime.current_secondary_phase = None
 
         if runtime.current_sweep_raw.size == 0:
-            if push_to_ring:
+            # A single empty/partial sweep (no points in the working range) must NOT
-                reset_ring_buffers()
+            # wipe the whole waterfall — that made the B-scan flash to zero and back
+            # (the "мерцание"/jumping max). Skip this frame and keep the existing ring
+            # history intact. Deliberate resets come through reset_ring=True (handled
+            # at the top of this function), so nothing to clear here.
+            if push_to_ring and not reset_ring:
+                log_debug_event("empty_sweep_skipped", "ui empty sweep skipped (ring preserved)")
             runtime.current_freqs = None
             runtime.current_sweep_raw = None
             runtime.current_fft_source = None
@@ -3853,7 +3877,27 @@ def run_pyqtgraph(args) -> None:
                         if levels is not None:
                             bscan_bg_levels_frozen["held"] = levels
                 else:
-                    # Normal view: constant manual dB window from the spin boxes.
+                    # Normal view: seed the manual window once from the first real
+                    # frame (unless the user gave an explicit --bscan-db-range), then
+                    # hold it fixed so the image never flickers.
+                    if not bscan_levels_seeded["done"]:
+                        try:
+                            lo = float(np.nanpercentile(disp_fft, 2.0))
+                            hi = float(np.nanpercentile(disp_fft, 98.0))
+                            if np.isfinite(lo) and np.isfinite(hi) and lo < hi:
+                                bscan_manual_levels["vmin"] = lo
+                                bscan_manual_levels["vmax"] = hi
+                                for _spin, _val in (
+                                    (bscan_db_min_spin, lo),
+                                    (bscan_db_max_spin, hi),
+                                ):
+                                    _spin.blockSignals(True)
+                                    _spin.setValue(_val)
+                                    _spin.blockSignals(False)
+                                bscan_levels_seeded["done"] = True
+                        except Exception:
+                            pass
+                    # Constant manual dB window from the spin boxes.
                     levels = (bscan_manual_levels["vmin"], bscan_manual_levels["vmax"])
                 disp_fft_display_axis = display_distance_axis_for_mode(disp_fft_axis, fft_mode)
                 if display_distance_transform_enabled(fft_mode) and disp_fft_display_axis.size == disp_fft.shape[0]: