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Add audio packing code.

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This commit is contained in:
Jonathan Naylor 2020-05-08 12:30:15 +01:00
parent 09b6929100
commit 880df2536d
2 changed files with 35 additions and 2 deletions
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35
FM.cpp
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@ -20,6 +20,11 @@
#include "Globals.h"
#include "FM.h"
const uint8_t BIT_MASK_TABLE[] = {0x80U, 0x40U, 0x20U, 0x10U, 0x08U, 0x04U, 0x02U, 0x01U};
#define WRITE_BIT_AUDIO(p,i,b) p[(i)>>3] = (b) ? (p[(i)>>3] | BIT_MASK_TABLE[(i)&7]) : (p[(i)>>3] & ~BIT_MASK_TABLE[(i)&7])
#define READ_BIT_AUDIO(p,i) (p[(i)>>3] & BIT_MASK_TABLE[(i)&7])
CFM::CFM() :
m_callsign(),
m_rfAck(),
@ -632,6 +637,34 @@ uint8_t CFM::getSpace() const
uint8_t CFM::writeData(const uint8_t* data, uint8_t length)
{
// Handle incoming external audio, in 12-bit packed form.
q15_t samples[170U];
uint8_t nSamples = 0U;
for (uint8_t i = 0U; i < length; i += 3U) {
uint16_t sample1 = 0U;
uint16_t sample2 = 0U;
uint16_t MASK = 0x0001U;
uint8_t* base = data + i;
for (uint8_t j = 0U; j < 12U; j++, MASK <<= 1) {
uint8_t pos1 = j;
uint8_t pos2 = j + 12U;
bool b1 = READ_BIT_AUDIO(base, pos1) != 0U;
bool b2 = READ_BIT_AUDIO(base, pos2) != 0U;
if (b1)
sample1 |= MASK;
if (b2)
sample2 |= MASK;
}
// Convert from uint16_t (0 - +4095) to Q15 (-2048 - +2047)
samples[nSamples++] = q15_t(sample1) - 2048;
samples[nSamples++] = q15_t(sample2) - 2048;
}
// Received audio is now in Q15 format in samples, with length nSamples.
return 0U;
}