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[fix](trx-wspr): fix reversed deinterleaving that prevented all decodes

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The deinterleave function had its indices swapped: it wrote
out[j] = symbols[p] instead of out[p] = symbols[j]. This fed
completely scrambled data to the Fano decoder, making convergence
impossible. Matched against the reference implementation in
raptor/lib/wsprd/wsprd_utils.c which does tmp[p] = sym[j].

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Stanislaw Grams <stanislawgrams@gmail.com>
This commit is contained in:
Stan Grams
2026-03-17 21:48:06 +01:00
parent 46415fa307
commit bcd3255ad7
1 changed files with 5 additions and 1 deletions
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src/decoders/trx-wspr/src/protocol.rs
+5 -1
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@@ -27,13 +27,17 @@ fn rev8(mut b: u8) -> u8 {
/// ///
/// In WSPR: symbol = sync_bit + 2*data_bit, so data_bit = symbol >> 1. /// In WSPR: symbol = sync_bit + 2*data_bit, so data_bit = symbol >> 1.
/// The 162 data bits are reordered via bit-reversal of 8-bit indices. /// The 162 data bits are reordered via bit-reversal of 8-bit indices.
///
/// The interleaving places coded bit p at transmitted position j = rev8(i)
/// (for each i in 0..255 where rev8(i) < 162). Deinterleaving reverses
/// this: coded[p] = transmitted[j] >> 1.
fn deinterleave(symbols: &[u8]) -> [u8; NSYMS] { fn deinterleave(symbols: &[u8]) -> [u8; NSYMS] {
let mut out = [0u8; NSYMS]; let mut out = [0u8; NSYMS];
let mut p = 0usize; let mut p = 0usize;
for i in 0u8..=255 { for i in 0u8..=255 {
let j = rev8(i) as usize; let j = rev8(i) as usize;
if j < NSYMS { if j < NSYMS {
out[j] = symbols[p] >> 1; out[p] = symbols[j] >> 1;
p += 1; p += 1;
} }
} }