##
## This file is part of the libsigrokdecode project.
##
## Copyright (C) 2014 Guenther Wenninger <robin@bitschubbser.org>
##
## This program is free software; you can redistribute it and/or modify
## it under the terms of the GNU General Public License as published by
## the Free Software Foundation; either version 2 of the License, or
## (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, see <http://www.gnu.org/licenses/>.
##
import sigrokdecode as srd
class SamplerateError(Exception):
pass
class Decoder(srd.Decoder):
api_version = 3
id = 'spdif'
name = 'S/PDIF'
longname = 'Sony/Philips Digital Interface Format'
desc = 'Serial bus for connecting digital audio devices.'
license = 'gplv2+'
inputs = ['logic']
outputs = []
tags = ['Audio', 'PC']
channels = (
{'id': 'data', 'name': 'Data', 'desc': 'Data line'},
)
annotations = (
('bitrate', 'Bitrate / baudrate'),
('preamble', 'Preamble'),
('bit', 'Bit'),
('aux', 'Auxillary-audio-databit'),
('sample', 'Audio Sample'),
('validity', 'Data Valid'),
('subcode', 'Subcode data'),
('chan_stat', 'Channnel Status'),
('parity', 'Parity Bit'),
)
annotation_rows = (
('bits', 'Bits', (2,)),
('info', 'Info', (0, 1, 3, 5, 6, 7, 8)),
('samples', 'Samples', (4,)),
)
def putx(self, ss, es, data):
self.put(ss, es, self.out_ann, data)
def puty(self, data):
self.put(self.ss_edge, self.samplenum, self.out_ann, data)
def __init__(self):
self.reset()
def reset(self):
self.state = 'GET FIRST PULSE WIDTH'
self.ss_edge = None
self.first_edge = True
self.samplenum_prev_edge = 0
self.pulse_width = 0
self.clocks = []
self.range1 = 0
self.range2 = 0
self.preamble_state = 0
self.preamble = []
self.seen_preamble = False
self.last_preamble = 0
self.bitrate_message_start = 0
self.bitrate_message_end = 0
self.frame_counter = 0
self.frame_start = 0
self.frame_length = 0
self.sampleratetmp = 1
self.first_one = True
self.subframe = []
def start(self):
self.out_ann = self.register(srd.OUTPUT_ANN)
def metadata(self, key, value):
if key == srd.SRD_CONF_SAMPLERATE:
self.samplerate = value
def get_pulse_type(self):
if self.pulse_width >= self.range2:
return 2
elif self.pulse_width >= self.range1:
return 0
else:
return 1
def find_first_pulse_width(self):
if self.pulse_width != 0:
self.clocks.append(self.pulse_width)
self.state = 'GET SECOND PULSE WIDTH'
self.puty([2, ['Found width 1: %d' % self.pulse_width, 'W1: %d' % self.pulse_width]])
self.ss_edge = self.samplenum
def find_second_pulse_width(self):
if self.pulse_width > (self.clocks[0] * 1.3) or \
self.pulse_width <= (self.clocks[0] * 0.75):
self.puty([2, ['Found width 2: %d' % self.pulse_width, 'W2: %d' % self.pulse_width]])
self.clocks.append(self.pulse_width)
self.state = 'GET THIRD PULSE WIDTH'
else:
self.puty([2, ['Search width 2: %d' % self.pulse_width, 'SW2: %d' % self.pulse_width]])
self.ss_edge = self.samplenum
def find_third_pulse_width(self):
if not ((self.pulse_width > (self.clocks[0] * 1.3) or \
self.pulse_width <= (self.clocks[0] * 0.75)) \
and (self.pulse_width > (self.clocks[1] * 1.3) or \
self.pulse_width <= (self.clocks[1] * 0.75))):
self.puty([2, ['Search width 3: %d' % self.pulse_width, 'SW3: %d' % self.pulse_width]])
self.ss_edge = self.samplenum
return
else:
self.puty([2, ['Found width 3: %d' % self.pulse_width, 'W3: %d' % self.pulse_width]])
self.ss_edge = self.samplenum
# The message of the calculated bitrate should start at this sample
# (right after the synchronisation).
self.bitrate_message_start = self.samplenum
self.clocks.append(self.pulse_width)
self.clocks.sort()
self.range1 = (self.clocks[0] + self.clocks[1]) / 2
self.range2 = (self.clocks[1] + self.clocks[2]) / 2
# Give some feedback during synchronisation and inform if sample rate
# is too low.
if self.clocks[0] <= 3:
self.putx(0, self.samplenum, [0, ['Short pulses detected. Increase sample rate!']])
raise SamplerateError('Short pulses detected')
else:
self.putx(0, self.samplenum, [0, ['Synchronisation']])
self.ss_edge = 0
# Mostly, the synchronisation ends with a long pulse because they
# appear rarely. A skip of the next pulse will then prevent a 'M'
# frame to be labeled an unknown preamble for the first decoded frame.
(data,) = self.wait({0: 'e'})
self.pulse_width = self.samplenum - self.samplenum_prev_edge
self.samplenum_prev_edge = self.samplenum
self.last_preamble = self.samplenum
# We are done recovering the clock, now let's decode the data stream.
self.state = 'DECODE STREAM'
def decode_stream(self):
pulse = self.get_pulse_type()
if not self.seen_preamble:
# This is probably the start of a preamble, decode it.
if pulse == 2:
self.preamble.append(self.get_pulse_type())
self.state = 'DECODE PREAMBLE'
self.ss_edge = self.samplenum - self.pulse_width
# Use the first ten frames to calculate bit rates
if self.frame_counter == 0:
# This is the first preamble to be decoded. Measurement of
# bit rates starts here.
self.frame_start = self.samplenum
# The bit rate message should end here.
self.bitrate_message_end = self.ss_edge
elif self.frame_counter == 10:
self.frame_length = self.samplenum - self.frame_start
# Use section between end of synchronisation and start of
# first preamble to show measured bit rates.
if self.samplerate:
self.putx(self.bitrate_message_start, self.bitrate_message_end,\
[0, ['Audio samplingrate: %6.2f kHz; Bit rate: %6.3f MBit/s' %\
((self.samplerate / 200 / self.frame_length), (self.samplerate / 200 * 64 / 1000 / self.frame_length))]])
else:
self.putx(self.bitrate_message_start, self.bitrate_message_end, [0, ['No sample rate given']])
self.frame_counter += 1
return
# We've seen a preamble.
if pulse == 1 and self.first_one:
self.first_one = False
self.subframe.append([pulse, self.samplenum - self.pulse_width, self.samplenum])
elif pulse == 1 and not self.first_one:
self.subframe[-1][2] = self.samplenum
self.putx(self.subframe[-1][1], self.samplenum, [2, ['1']])
self.bitcount += 1
self.first_one = True
else:
self.subframe.append([pulse, self.samplenum - self.pulse_width, self.samplenum])
self.putx(self.samplenum - self.pulse_width, self.samplenum, [2, ['0']])
self.bitcount += 1
if self.bitcount == 28:
aux_audio_data = self.subframe[0:4]
sam, sam_rot = '', ''
for a in aux_audio_data:
sam = sam + str(a[0])
sam_rot = str(a[0]) + sam_rot
sample = self.subframe[4:24]
for s in sample:
sam = sam + str(s[0])
sam_rot = str(s[0]) + sam_rot
validity = self.subframe[24:25]
subcode_data = self.subframe[25:26]
channel_status = self.subframe[26:27]
parity = self.subframe[27:28]
self.putx(aux_audio_data[0][1], aux_audio_data[3][2], \
[3, ['Aux 0x%x' % int(sam, 2), '0x%x' % int(sam, 2)]])
self.putx(sample[0][1], sample[19][2], \
[3, ['Sample 0x%x' % int(sam, 2), '0x%x' % int(sam, 2)]])
self.putx(aux_audio_data[0][1], sample[19][2], \
[4, ['Audio 0x%x' % int(sam_rot, 2), '0x%x' % int(sam_rot, 2)]])
if validity[0][0] == 0:
self.putx(validity[0][1], validity[0][2], [5, ['V']])
else:
self.putx(validity[0][1], validity[0][2], [5, ['E']])
self.putx(subcode_data[0][1], subcode_data[0][2],
[6, ['S: %d' % subcode_data[0][0]]])
self.putx(channel_status[0][1], channel_status[0][2],
[7, ['C: %d' % channel_status[0][0]]])
self.putx(parity[0][1], parity[0][2], [8, ['P: %d' % parity[0][0]]])
self.subframe = []
self.seen_preamble = False
self.bitcount = 0
def decode_preamble(self):
if self.preamble_state == 0:
self.preamble.append(self.get_pulse_type())
self.preamble_state = 1
elif self.preamble_state == 1:
self.preamble.append(self.get_pulse_type())
self.preamble_state = 2
elif self.preamble_state == 2:
self.preamble.append(self.get_pulse_type())
self.preamble_state = 0
self.state = 'DECODE STREAM'
if self.preamble == [2, 0, 1, 0]:
self.puty([1, ['Preamble W', 'W']])
elif self.preamble == [2, 2, 1, 1]:
self.puty([1, ['Preamble M', 'M']])
elif self.preamble == [2, 1, 1, 2]:
self.puty([1, ['Preamble B', 'B']])
else:
self.puty([1, ['Unknown Preamble', 'Unknown Prea.', 'U']])
self.preamble = []
self.seen_preamble = True
self.bitcount = 0
self.first_one = True
self.last_preamble = self.samplenum
def decode(self):
# Set samplerate to 0 if it is not given. Decoding is still possible.
if not self.samplerate:
self.samplerate = 0
# Throw away first two edges as it might be mangled data.
self.wait({0: 'e'})
self.wait({0: 'e'})
self.ss_edge = 0
self.puty([2, ['Skip']])
self.ss_edge = self.samplenum
self.samplenum_prev_edge = self.samplenum
while True:
# Wait for any edge (rising or falling).
(data,) = self.wait({0: 'e'})
self.pulse_width = self.samplenum - self.samplenum_prev_edge
self.samplenum_prev_edge = self.samplenum
if self.state == 'GET FIRST PULSE WIDTH':
self.find_first_pulse_width()
elif self.state == 'GET SECOND PULSE WIDTH':
self.find_second_pulse_width()
elif self.state == 'GET THIRD PULSE WIDTH':
self.find_third_pulse_width()
elif self.state == 'DECODE STREAM':
self.decode_stream()
elif self.state == 'DECODE PREAMBLE':
self.decode_preamble()