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Fix SSTV decoder thread lifecycle and VIS detection reliability

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Three bugs preventing the live SSTV pipeline from working:

1. Race condition: self._running was set AFTER starting the decode
   thread, so the thread checked the flag, found it False, and exited
   immediately without ever processing audio.

2. Ghost running state: when the decode thread exited (e.g. rtl_fm
   died), self._running stayed True. The decoder reported as running
   but was dead, and subsequent start() calls returned without doing
   anything - permanently stuck until app restart.

3. VIS detection fragility: unclassifiable windows at tone transition
   boundaries (mixed energy from two tones) caused the state machine
   to reset from LEADER/BREAK states back to IDLE, dropping valid
   VIS headers on real signals.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Smittix
2026-02-07 10:33:08 +00:00
parent ef7d8cca9f
commit 28891f4709
2 changed files with 30 additions and 2 deletions
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6
utils/sstv/vis.py
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@@ -193,6 +193,8 @@ class VISDetector:
# Transition to BREAK; this window counts as break window 1
self._tone_counter = 1
self._state = VISState.BREAK
elif tone is None:
pass # Ambiguous window at tone boundary — stay in state
else:
self._tone_counter = 0
self._state = VISState.IDLE
@@ -207,6 +209,8 @@ class VISDetector:
# Transition to LEADER_2; this window counts
self._tone_counter = 1
self._state = VISState.LEADER_2
elif tone is None:
pass # Ambiguous window at tone boundary — stay in state
else:
self._tone_counter = 0
self._state = VISState.IDLE
@@ -227,6 +231,8 @@ class VISDetector:
self._data_bits = []
self._bit_accumulator = []
self._state = VISState.DATA_BITS
elif tone is None:
pass # Ambiguous window at tone boundary — stay in state
else:
self._tone_counter = 0
self._state = VISState.IDLE