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sstvdec
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Improve header search formatting

master
colaclanth 2019-07-15 21:40:08 +01:00
parent 45f7309448
commit 3fdea12bfd
2 changed files with 36 additions and 18 deletions
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3
sstv/command.py
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@ -95,6 +95,9 @@ examples:
def start(self):
with SSTVDecoder(self._audio_file) as sstv:
img = sstv.decode()
if img is None: # No SSTV signal found
exit(2)
try:
img.save(self._output_file)
except (KeyError, ValueError):

51
sstv/decode.py
View File

@ -35,7 +35,7 @@ class SSTVDecoder(object):
def decode(self, skip=0):
"""Attempts to decode the audio data as an SSTV signal
Returns a PIL image on success, and None on error
Returns a PIL image on success, and None if no SSTV signal was found
"""
if skip > 0:
@ -104,13 +104,21 @@ class SSTVDecoder(object):
def _find_header(self):
"""Finds the approx sample of the calibration header"""
break_sample = round(spec.BREAK_OFFSET * self._sample_rate)
leader_sample = round(spec.LEADER_OFFSET * self._sample_rate)
vis_start_sample = round(spec.VIS_START_OFFSET * self._sample_rate)
header_size = round(spec.HDR_SIZE * self._sample_rate)
window_size = round(spec.HDR_WINDOW_SIZE * self._sample_rate)
leader_1_sample = 0
leader_1_search = leader_1_sample + window_size
break_sample = round(spec.BREAK_OFFSET * self._sample_rate)
break_search = break_sample + window_size
leader_2_sample = round(spec.LEADER_OFFSET * self._sample_rate)
leader_2_search = leader_2_sample + window_size
vis_start_sample = round(spec.VIS_START_OFFSET * self._sample_rate)
vis_start_search = vis_start_sample + window_size
jump_size = round(0.002 * self._sample_rate) # check every 2ms
# The margin of error created here will be negligible when decoding the
@ -119,26 +127,33 @@ class SSTVDecoder(object):
current_sample = 0
for sample in self._samples[:-header_size+window_size]:
for current_sample in range(0, len(self._samples) - header_size,
jump_size):
if current_sample % (jump_size * 256) == 0:
log_message("Searching for calibration header... {:.1f}s".format(
current_sample / self._sample_rate), self.log_basic, recur=True)
search_msg = "Searching for calibration header... {:.1f}s"
progress = current_sample / self._sample_rate
log_message(search_msg.format(progress), recur=True)
search_area = self._samples[current_sample:current_sample+header_size]
search_end = current_sample + header_size
search_area = self._samples[current_sample:search_end]
if abs(self._peak_fft_freq(search_area[0:window_size]) - 1900) < 50 and \
abs(self._peak_fft_freq(search_area[break_sample:break_sample+window_size]) - 1200) < 50 and \
abs(self._peak_fft_freq(search_area[leader_sample:leader_sample+window_size]) - 1900) < 50 and \
abs(self._peak_fft_freq(search_area[vis_start_sample:vis_start_sample+window_size]) - 1200) < 50:
leader_1_area = search_area[leader_1_sample:leader_1_search]
break_area = search_area[break_sample:break_search]
leader_2_area = search_area[leader_2_sample:leader_2_search]
vis_start_area = search_area[vis_start_sample:vis_start_search]
log_message("Searching for calibration header... Found!{:>4}".format(
' '), self.log_basic)
if (abs(self._peak_fft_freq(leader_1_area) - 1200) < 50
and abs(self._peak_fft_freq(break_area) - 1900) < 50
and abs(self._peak_fft_freq(leader_2_area) - 1900) < 50
and abs(self._peak_fft_freq(vis_start_area) - 1200) < 50):
stop_msg = "Searching for calibration header... Found!{:>4}"
log_message(stop_msg.format(' '))
return current_sample
current_sample += jump_size
log_message()
log_message("Couldn't find SSTV header in the given audio file.")
log_message("Couldn't find SSTV header in the given audio file",
err=True)
return None
def _decode_vis(self, vis_section):