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Simplify YSF V/D mode 2 audio FEC regeneration.

This commit is contained in:
Jonathan Naylor 2017-01-10 15:06:31 +00:00 committed by GitHub
parent cdb54779f2
commit dce50e4cde
1 changed files with 29 additions and 12 deletions
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41
YSFPayload.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (C) 2016 Jonathan Naylor, G4KLX
* Copyright (C) 2016,2017 Jonathan Naylor, G4KLX
* Copyright (C) 2016 Mathias Weyland, HB9FRV
*
* This program is free software; you can redistribute it and/or modify
@ -397,12 +397,14 @@ unsigned int CYSFPayload::processVDMode2Audio(unsigned char* data)
// We have a total of 5 VCH sections, iterate through each
for (unsigned int j = 0U; j < 5U; j++, offset += 144U) {
unsigned int errs = 0U;
unsigned char vch[13U];
// Deinterleave
for (unsigned int i = 0U; i < 104U; i++) {
unsigned int n = INTERLEAVE_TABLE_26_4[i];
bool s = READ_BIT1(data, offset + n) != 0x00U;
bool s = READ_BIT1(data, offset + n);
WRITE_BIT1(vch, i, s);
}
@ -413,19 +415,34 @@ unsigned int CYSFPayload::processVDMode2Audio(unsigned char* data)
// errors += READ_BIT1(vch, 103); // Padding bit must be zero but apparently it is not...
for (unsigned int i = 0U; i < 81U; i += 3) {
uint8_t vote = bool(READ_BIT1(vch, i)) + bool(READ_BIT1(vch, i + 1)) + bool(READ_BIT1(vch, i + 2));
if (vote == 1 || vote == 2) {
bool decision = vote / 2; // exploit integer division: 1/2 == 0, 2/2 == 1.
WRITE_BIT1(vch, i, decision);
WRITE_BIT1(vch, i + 1, decision);
WRITE_BIT1(vch, i + 2, decision);
errors++;
uint8_t vote = 0U;
vote += READ_BIT1(vch, i + 0U) ? 1U : 0U;
vote += READ_BIT1(vch, i + 1U) ? 1U : 0U;
vote += READ_BIT1(vch, i + 2U) ? 1U : 0U;
switch (vote) {
case 1U: // 1 0 0, or 0 1 0, or 0 0 1, convert to 0 0 0
WRITE_BIT1(vch, i + 0U, false);
WRITE_BIT1(vch, i + 1U, false);
WRITE_BIT1(vch, i + 2U, false);
errs++;
break;
case 2U: // 1 1 0, or 0 1 1, or 1 0 1, convert to 1 1 1
WRITE_BIT1(vch, i + 0U, true);
WRITE_BIT1(vch, i + 1U, true);
WRITE_BIT1(vch, i + 2U, true);
errs++;
break;
default: // 0U (0 0 0), or 3U (1 1 1), no errors
break;
}
}
// Reconstruct only if we have bit errors. Technically we could even
// constrain it individually to the 5 VCH sections.
if (errors > 0U) {
// Reconstruct only if we have bit errors.
if (errs > 0U) {
// Accumulate the total number of errors
errors += errs;
// Scramble
for (unsigned int i = 0U; i < 13U; i++)
vch[i] ^= WHITENING_DATA[i];