/*
AudioOutput
Base class of an audio output player
Copyright (C) 2017 Earle F. Philhower, III
*/
#pragma once
#include "AudioStatus.h"
#include <stdint.h> // int16_t
class AudioOutput
{
public:
virtual bool SetRate(int hz) { hertz = hz; return true; }
virtual bool SetBitsPerSample(int bits) { bps = bits; return true; }
virtual bool SetChannels(int chan) { channels = chan; return true; }
virtual bool SetGain(float f) { if (f>4.0) f = 4.0; if (f<0.0) f=0.0; gainF2P6 = (uint8_t)(f*(1<<6)); return true; }
virtual bool begin() { return false; };
typedef enum { LEFTCHANNEL=0, RIGHTCHANNEL=1 } SampleIndex;
virtual bool ConsumeSample(int16_t sample[2]) { (void)sample; return false; }
virtual uint16_t ConsumeSamples(int16_t *samples, uint16_t count)
{
for (uint16_t i=0; i<count; i++) {
if (!ConsumeSample(samples)) return i;
samples += 2;
}
return count;
}
virtual bool stop() { return false; }
virtual bool loop() { return true; }
public:
virtual bool RegisterMetadataCB(AudioStatus::metadataCBFn fn, void *data) { return cb.RegisterMetadataCB(fn, data); }
virtual bool RegisterStatusCB(AudioStatus::statusCBFn fn, void *data) { return cb.RegisterStatusCB(fn, data); }
protected:
void MakeSampleStereo16(int16_t sample[2]) {
// Mono to "stereo" conversion
if (channels == 1)
sample[RIGHTCHANNEL] = sample[LEFTCHANNEL];
if (bps == 8) {
// Upsample from unsigned 8 bits to signed 16 bits
sample[LEFTCHANNEL] = (((int16_t)(sample[LEFTCHANNEL]&0xff)) - 128) << 8;
sample[RIGHTCHANNEL] = (((int16_t)(sample[RIGHTCHANNEL]&0xff)) - 128) << 8;
}
};
inline int16_t Amplify(int16_t s) {
int32_t v = (s * gainF2P6)>>6;
if (v < -32767) return -32767;
else if (v > 32767) return 32767;
else return (int16_t)(v&0xffff);
}
protected:
uint16_t hertz;
uint8_t bps;
uint8_t channels;
uint8_t gainF2P6; // Fixed point 2.6
protected:
AudioStatus cb;
};
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