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sstvdec
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Changed vis decode to return end of header

master
colaclanth 2019-07-15 22:02:59 +01:00
parent 3fdea12bfd
commit 4f91c52658
1 changed files with 12 additions and 13 deletions
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25
sstv/decode.py
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@ -41,14 +41,13 @@ class SSTVDecoder(object):
if skip > 0:
self._samples = self._samples[skip:]
header_start = self._find_header()
header_end = self._find_header()
if header_start is None:
if header_end is None:
return None
vis_start = header_start + round(spec.HDR_SIZE * self._sample_rate)
vis_end = vis_start + round(spec.VIS_BIT_SIZE * 9 * self._sample_rate)
vis_section = self._samples[vis_start:vis_end]
vis_end = header_end + round(spec.VIS_BIT_SIZE * 9 * self._sample_rate)
vis_section = self._samples[header_end:vis_end]
self.mode = self._decode_vis(vis_section)
@ -102,7 +101,7 @@ class SSTVDecoder(object):
return peak * self._sample_rate / len(windowed_data)
def _find_header(self):
"""Finds the approx sample of the calibration header"""
"""Finds the approx sample of the end of the calibration header"""
header_size = round(spec.HDR_SIZE * self._sample_rate)
window_size = round(spec.HDR_WINDOW_SIZE * self._sample_rate)
@ -142,14 +141,14 @@ class SSTVDecoder(object):
leader_2_area = search_area[leader_2_sample:leader_2_search]
vis_start_area = search_area[vis_start_sample:vis_start_search]
if (abs(self._peak_fft_freq(leader_1_area) - 1200) < 50
and abs(self._peak_fft_freq(break_area) - 1900) < 50
if (abs(self._peak_fft_freq(leader_1_area) - 1900) < 50
and abs(self._peak_fft_freq(break_area) - 1200) < 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
return current_sample + header_size
log_message()
log_message("Couldn't find SSTV header in the given audio file",
@ -158,6 +157,7 @@ class SSTVDecoder(object):
def _decode_vis(self, vis_section):
"""Decodes the vis from the audio data and returns the SSTV mode"""
bit_size = round(spec.VIS_BIT_SIZE * self._sample_rate)
vis_bits = []
@ -170,8 +170,7 @@ class SSTVDecoder(object):
# check for even parity in last bit
parity = sum(vis_bits) % 2 == 0
if not parity:
log_message("Error decoding VIS header (incorrect parity bit)")
return None
raise ValueError("error decoding VIS header (invalid parity bit)")
# LSB first so we must reverse and ignore the parity bit
vis_value = 0
@ -179,8 +178,8 @@ class SSTVDecoder(object):
vis_value = (vis_value << 1) | bit
if vis_value not in spec.VIS_MAP:
log_message("SSTV mode is unsupported (VIS: {})".format(vis_value))
return None
error = "SSTV mode is unsupported (VIS: {})"
raise ValueError(error.format(vis_value))
mode = spec.VIS_MAP[vis_value]
log_message("Detected SSTV mode {}".format(mode.NAME))