diff --git a/utils/sstv/image_decoder.py b/utils/sstv/image_decoder.py
index 13a9eda..c7f2391 100644
--- a/utils/sstv/image_decoder.py
+++ b/utils/sstv/image_decoder.py
@@ -138,9 +138,16 @@ class SSTVImageDecoder:
 
         self._buffer = np.concatenate([self._buffer, samples])
 
-        # Process complete lines
+        # Process complete lines.
+        # Guard against stalls: if _decode_line() cannot consume data
+        # (e.g. sub-component samples exceed line_samples due to rounding),
+        # break out and wait for more audio.
         while not self._complete and len(self._buffer) >= self._line_samples:
+            prev_line = self._current_line
+            prev_len = len(self._buffer)
             self._decode_line()
+            if self._current_line == prev_line and len(self._buffer) == prev_len:
+                break  # No progress — need more data
 
         # Prevent unbounded buffer growth - keep at most 2 lines worth
         max_buffer = self._line_samples * 2
diff --git a/utils/sstv/sstv_decoder.py b/utils/sstv/sstv_decoder.py
index 9daa9ac..36834bc 100644
--- a/utils/sstv/sstv_decoder.py
+++ b/utils/sstv/sstv_decoder.py
@@ -487,9 +487,14 @@ class SSTVDecoder:
                         sync_energy = goertzel_mag(samples, 1200.0, SAMPLE_RATE)
                         noise_floor = max(rms * 0.5, 0.001)
 
-                        if leader_energy > noise_floor * 5:
+                        # Require the tone to both exceed the noise floor AND
+                        # dominate the other tone by 2x to avoid false positives
+                        # from broadband noise.
+                        if (leader_energy > noise_floor * 5
+                                and leader_energy > sync_energy * 2):
                             sstv_tone = 'leader'
-                        elif sync_energy > noise_floor * 5:
+                        elif (sync_energy > noise_floor * 5
+                              and sync_energy > leader_energy * 2):
                             sstv_tone = 'sync'
                         elif signal_level > 10:
                             sstv_tone = 'noise'