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-rw-r--r--src/TII.cpp24
1 files changed, 19 insertions, 5 deletions
diff --git a/src/TII.cpp b/src/TII.cpp
index 4ed1a91..4710ed4 100644
--- a/src/TII.cpp
+++ b/src/TII.cpp
@@ -197,16 +197,30 @@ int TII::process(Buffer* dataIn, Buffer* dataOut)
complexf* in = reinterpret_cast<complexf*>(dataIn->getData());
complexf* out = reinterpret_cast<complexf*>(dataOut->getData());
+ if ((m_enabled_carriers.size() % 2) != 0) {
+ throw std::logic_error("odd number of enabled carriers");
+ }
+
+ /* Normalise the TII carrier power according to ETSI TR 101 496-3
+ * Clause 5.4.2.2 Paragraph 7:
+ *
+ * > The ratio of carriers in a TII symbol to a normal DAB symbol
+ * > is 1:48 for all Modes, so that the signal power in a TII symbol is
+ * > 16 dB below the signal power of the other symbols.
+ *
+ * We need to normalise to the square root of 48 because we touch I and
+ * Q separately.
+ */
+ const float normalise_factor = 0.14433756729740644112f; // = 1/sqrt(48)
+
for (size_t i = 0; i < m_enabled_carriers.size(); i+=2) {
- //BAD implementation:
- // setting exactly the same phase of the signal for lower adjacent
- // frequency
+ // See header file for an explanation of the old variant
if (m_enabled_carriers[i]) {
- out[i] = (m_conf.old_variant ? in[i+1] : in[i])/((float)48.0);
+ out[i] = normalise_factor * (m_conf.old_variant ? in[i+1] : in[i]);
}
if (m_enabled_carriers[i+1]) {
- out[i+1] = in[i+1]/((float)48.0);
+ out[i+1] = normalise_factor * in[i+1];
}
}
}