Add preemphasis and deemphasis
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dc9e6ade23
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2 changed files with 13 additions and 5 deletions
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@ -20,14 +20,13 @@
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#include <string>
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const uint8_t BIT_MASK_TABLE[] = { 0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U };
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#define WRITE_BIT(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
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#define READ_BIT(p,i) (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])
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#define EMPHASIS_GAIN_DB 0 //Gain needs to be the same for pre an deeemphasis
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CFMControl::CFMControl(CFMNetwork* network) :
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m_network(network),
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m_enabled(false)
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m_enabled(false),
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m_preemphasis(0.3889703087993727F, -0.3290005228984741F, 0.0F, 1.0F, 0.282029168302153F, 0.0F, EMPHASIS_GAIN_DB),
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m_deemphasis(1.0F, 0.282029168302153F, 0.0F, 0.3889703087993727F, -0.3290005228984741F, 0.0F, EMPHASIS_GAIN_DB)
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{
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assert(network != NULL);
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}
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@ -67,6 +66,9 @@ bool CFMControl::writeModem(const unsigned char* data, unsigned int length)
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}
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// De-emphasise the data and any other processing needed (maybe a low-pass filter to remove the CTCSS)
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for(unsigned int i = 0U; i < nSamples; i++) {
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samples[i] = m_deemphasis.filter(samples[i]);
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}
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unsigned char out[350U];
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unsigned int nOut = 0U;
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@ -102,6 +104,9 @@ unsigned int CFMControl::readModem(unsigned char* data, unsigned int space)
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}
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// Pre-emphasise the data and other stuff.
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for(unsigned int i = 0U; i < nSamples; i++) {
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samples[i] = m_preemphasis.filter(samples[i]);
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}
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// Pack the floating point data (+1.0 to -1.0) to packed 12-bit samples (+2047 - -2048)
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unsigned int pack = 0U;
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@ -21,6 +21,7 @@
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#include "FMNetwork.h"
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#include "Defines.h"
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#include "IIRDirectForm1Filter.h"
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class CFMControl {
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public:
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@ -38,6 +39,8 @@ public:
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private:
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CFMNetwork* m_network;
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bool m_enabled;
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CIIRDirectForm1Filter m_preemphasis;
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CIIRDirectForm1Filter m_deemphasis;
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};
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#endif
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