v1.8.0: Audio 代码重构与低功耗优化 (#943)

* Reconstruct Audio Code

* Remove old IoT implementation

* Add MQTT-UDP documentation

* OTA升级失败时，可以继续使用

main/audio/codecs/no_audio_codec.h

@@ -0,0 +1,35 @@
+#ifndef _NO_AUDIO_CODEC_H
+#define _NO_AUDIO_CODEC_H
+
+#include "audio_codec.h"
+
+#include <driver/gpio.h>
+#include <driver/i2s_pdm.h>
+
+class NoAudioCodec : public AudioCodec {
+private:
+    virtual int Write(const int16_t* data, int samples) override;
+    virtual int Read(int16_t* dest, int samples) override;
+
+public:
+    virtual ~NoAudioCodec();
+};
+
+class NoAudioCodecDuplex : public NoAudioCodec {
+public:
+    NoAudioCodecDuplex(int input_sample_rate, int output_sample_rate, gpio_num_t bclk, gpio_num_t ws, gpio_num_t dout, gpio_num_t din);
+};
+
+class NoAudioCodecSimplex : public NoAudioCodec {
+public:
+    NoAudioCodecSimplex(int input_sample_rate, int output_sample_rate, gpio_num_t spk_bclk, gpio_num_t spk_ws, gpio_num_t spk_dout, gpio_num_t mic_sck, gpio_num_t mic_ws, gpio_num_t mic_din);
+    NoAudioCodecSimplex(int input_sample_rate, int output_sample_rate, gpio_num_t spk_bclk, gpio_num_t spk_ws, gpio_num_t spk_dout, i2s_std_slot_mask_t spk_slot_mask, gpio_num_t mic_sck, gpio_num_t mic_ws, gpio_num_t mic_din, i2s_std_slot_mask_t mic_slot_mask);
+};
+
+class NoAudioCodecSimplexPdm : public NoAudioCodec {
+public:
+    NoAudioCodecSimplexPdm(int input_sample_rate, int output_sample_rate, gpio_num_t spk_bclk, gpio_num_t spk_ws, gpio_num_t spk_dout, gpio_num_t mic_sck,  gpio_num_t mic_din);
+    int Read(int16_t* dest, int samples);
+};
+
+#endif // _NO_AUDIO_CODEC_H