Mirror/intercept
1
0
Fork 0
mirror of https://github.com/smittix/intercept.git synced 2026-04-24 14:50:00 -07:00
Code Issues Packages Projects Releases Wiki Activity

fix: Preserve image-start samples across VIS-to-decoder boundary

Browse Source 
VISDetector._process_window() was calling self.reset() inside the
STOP_BIT handler, wiping self._buffer before feed() could advance
past the triggering window. All audio samples buffered after the
VIS STOP_BIT (the start of the first scan line) were silently
discarded, causing the image decoder to begin decoding mid-stream
with no alignment reference. The result was every scan line being
desynchronised from the first, producing the diagonal stripes and
scrambled colours seen in decoded images.

Fix: remove the premature reset() from _process_window(). The
STOP_BIT handler now sets state=DETECTED and returns the result.
A new remaining_buffer property exposes the post-VIS samples.
_decode_audio_stream() and decode_file() capture those samples
before calling reset(), then immediately feed them into the newly
created SSTVImageDecoder so decoding begins from sample 0 of
the first sync pulse.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
This commit is contained in:
Smittix
2026-02-18 19:06:32 +00:00
parent 37d24a539d
commit f29ae3d5a8
2 changed files with 37 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

17
utils/sstv/sstv_decoder.py
View File

@@ -464,7 +464,13 @@ class SSTVDecoder:
result = vis_detector.feed(samples)
if result is not None:
vis_code, mode_name = result
logger.info(f"VIS detected: code={vis_code}, mode={mode_name}")
# Capture samples that arrived after the VIS STOP_BIT —
# these are the start of the image and must be fed into
# the image decoder before the next chunk arrives.
remaining = vis_detector.remaining_buffer.copy()
vis_detector.reset()
logger.info(f"VIS detected: code={vis_code}, mode={mode_name}, "
f"{len(remaining)} image-start samples retained")
mode_spec = get_mode(vis_code)
if mode_spec:
@@ -473,6 +479,8 @@ class SSTVDecoder:
mode_spec,
sample_rate=SAMPLE_RATE,
)
if len(remaining) > 0:
image_decoder.feed(remaining)
self._emit_progress(DecodeProgress(
status='decoding',
mode=mode_name,
@@ -481,7 +489,6 @@ class SSTVDecoder:
))
else:
logger.warning(f"No mode spec for VIS code {vis_code}")
vis_detector.reset()
# Emit signal level metrics every ~500ms (every 5th 100ms chunk)
scope_tone: str | None = None
@@ -853,6 +860,8 @@ class SSTVDecoder:
result = vis_detector.feed(chunk)
if result is not None:
vis_code, mode_name = result
remaining = vis_detector.remaining_buffer.copy()
vis_detector.reset()
logger.info(f"VIS detected in file: code={vis_code}, mode={mode_name}")
mode_spec = get_mode(vis_code)
@@ -862,8 +871,8 @@ class SSTVDecoder:
mode_spec,
sample_rate=SAMPLE_RATE,
)
else:
vis_detector.reset()
if len(remaining) > 0:
image_decoder.feed(remaining)
except wave.Error as e:
logger.error(f"Error reading WAV file: {e}")