Add Biquad IIR DSP function and use a namespace (#12)

* add biquad IIR filter assembly functions

* use esp_audio_libs global namespace

Author: Kevin Ahrendt

README.md

@@ -1,7 +1,7 @@
 # esp-audio-libs
 
 A collection of libraries and functions that are useful for playing audio on ESP32 devices. It includes code based on the following:
-- [esp-dsp](https://github.com/espressif/esp-dsp) assembly functions for floating point dot products and Q15 fixed point addition and constant multipliction.
+- [esp-dsp](https://github.com/espressif/esp-dsp) assembly functions for floating point dot product and biquad IIR filters and Q15 fixed point addition and constant multipliction.
     - Author: Espressif
     - License: Apache v2.0
 - [ART-resampler](https://github.com/dbry/audio-resampler) for resampling audio, optimized with assembly dot product functions.

include/art_biquad.h

@@ -7,36 +7,34 @@
 //      Distributed under the BSD Software License (see license.txt)      //
 ////////////////////////////////////////////////////////////////////////////
 
-// biquad.h
+#pragma once
 
 #include <stdlib.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <math.h>
 
-typedef struct {
-  float a0, a1, a2, b1, b2;
-} BiquadCoefficients;
+namespace esp_audio_libs {
+namespace art_resampler {
 
-typedef struct {
-  BiquadCoefficients coeffs;  // coefficients
-  float in_d1, in_d2;         // delayed input
-  float out_d1, out_d2;       // delayed output
-  int first_order;            // optimization
-} Biquad;
+  typedef struct {
+    float a0, a1, a2, b1, b2;
+  } BiquadCoefficients;
 
-#ifdef __cplusplus
-extern "C" {
-#endif
+  typedef struct {
+    BiquadCoefficients coeffs;  // coefficients
+    float in_d1, in_d2;         // delayed input
+    float out_d1, out_d2;       // delayed output
+    int first_order;            // optimization
+  } Biquad;
 
-void biquad_init(Biquad *f, const BiquadCoefficients *coeffs, float gain);
+  void biquad_init(Biquad * f, const BiquadCoefficients *coeffs, float gain);
 
-void biquad_lowpass(BiquadCoefficients *filter, double frequency);
-void biquad_highpass(BiquadCoefficients *filter, double frequency);
+  void biquad_lowpass(BiquadCoefficients * filter, double frequency);
+  void biquad_highpass(BiquadCoefficients * filter, double frequency);
 
-void biquad_apply_buffer(Biquad *f, float *buffer, int num_samples, int stride);
-float biquad_apply_sample(Biquad *f, float input);
+  void biquad_apply_buffer(Biquad * f, float *buffer, int num_samples, int stride);
+  float biquad_apply_sample(Biquad * f, float input);
 
-#ifdef __cplusplus
 }
-#endif
+}  // namespace esp_audio_libs

include/art_resampler.h

@@ -16,6 +16,9 @@
 #include <math.h>
 #include <stdbool.h>
 
+namespace esp_audio_libs {
+namespace art_resampler {
+
 #define SUBSAMPLE_INTERPOLATE 0x1
 #define BLACKMAN_HARRIS 0x2
 #define INCLUDE_LOWPASS 0x4
@@ -30,10 +33,6 @@ typedef struct {
   unsigned int input_used, output_generated;
 } ResampleResult;
 
-#ifdef __cplusplus
-extern "C" {
-#endif
-
 Resample *resampleInit(int numChannels, int numTaps, int numFilters, float lowpassRatio, int flags);
 ResampleResult resampleProcess(Resample *cxt, const float *const *input, int numInputFrames, float *const *output,
                                int numOutputFrames, float ratio);
@@ -46,6 +45,5 @@ float resampleGetPosition(Resample *cxt);
 void resampleReset(Resample *cxt);
 void resampleFree(Resample *cxt);
 
-#ifdef __cplusplus
-}
-#endif
+}  // namespace art_resampler
+}  // namespace esp_audio_libs

include/flac_decoder.h

@@ -4,13 +4,13 @@
 // Uses some small parts from: https://github.com/schreibfaul1/ESP32-audioI2S/
 // See also: https://xiph.org/flac/format.html
 
-#ifndef _FLAC_DECODER_H
-#define _FLAC_DECODER_H
+#pragma once
 
 #include <cstddef>
 #include <cstdint>
 #include <vector>
 
+namespace esp_audio_libs {
 namespace flac {
 
 // 'fLaC'
@@ -185,5 +185,4 @@ class FLACDecoder {
 };
 
 }  // namespace flac
-
-#endif
+}  // namespace esp_audio_libs

include/mp3_decoder.h

@@ -1,10 +1,12 @@
-#ifndef MP3_DECODER_H_
-#define MP3_DECODER_H_
+#pragma once
 
 #include <stdlib.h>
 #include <string.h>
 #include <xtensa/config/core-isa.h>
 
+namespace esp_audio_libs {
+namespace helix_decoder {
+
 #define ASSERT(x) /* do nothing */
 
 /* determining MAINBUF_SIZE:
@@ -379,4 +381,5 @@ void MP3GetLastFrameInfo(HMP3Decoder hMP3Decoder, MP3FrameInfo *mp3FrameInfo);
 int MP3GetNextFrameInfo(HMP3Decoder hMP3Decoder, MP3FrameInfo *mp3FrameInfo, unsigned char *buf);
 int MP3FindSyncWord(unsigned char *buf, int nBytes);
 
-#endif  // MP3_DECODER_H_
+}  // namespace helix_decoder
+}  // namespace esp_audio_libs

include/resampler.h

@@ -8,6 +8,7 @@
 #include <algorithm>
 #include <esp_heap_caps.h>
 
+namespace esp_audio_libs {
 namespace resampler {
 
 // Class that wraps the ART resampler for straightforward use
@@ -59,10 +60,10 @@ class Resampler {
   float *float_output_buffer_{nullptr};
   size_t output_buffer_samples_;
 
-  Resample *resampler_{nullptr};
+  art_resampler::Resample *resampler_{nullptr};
 
-  Biquad lowpass_[2][2];
-  BiquadCoefficients lowpass_coeff_;
+  art_resampler::Biquad lowpass_[2][2];
+  art_resampler::BiquadCoefficients lowpass_coeff_;
 
   uint16_t number_of_taps_;
   uint16_t number_of_filters_;
@@ -79,3 +80,4 @@ class Resampler {
   uint8_t channels_;
 };
 }  // namespace resampler
+}  // namespace esp_audio_libs

include/utils.h

@@ -3,6 +3,8 @@
 #include <cmath>
 #include <stdint.h>
 
+namespace esp_audio_libs {
+
 /// @brief Converts an array of quantized samples with the specified number of bits into floating point samples.
 /// @param input_buffer Pointer to the input quantized samples aligned to the byte
 /// @param output_buffer Poitner to the output floating point samples
@@ -18,4 +20,7 @@ void quantized_to_float(const uint8_t *input_buffer, float *output_buffer, uint3
 /// @param num_samples Number of samples to convert
 /// @param output_bits Number of bits per sample for the quantized samples
 /// @return Number of clipped samples
-uint32_t float_to_quantized(const float *input_buffer, uint8_t *output_buffer, uint32_t num_samples, uint8_t output_bits);
+uint32_t float_to_quantized(const float *input_buffer, uint8_t *output_buffer, uint32_t num_samples,
+                            uint8_t output_bits);
+
+}  // namespace esp_audio_libs

include/wav_decoder.h

@@ -2,8 +2,7 @@
 // data portion of the file.
 // Skips over extraneous chunks like LIST and INFO.
 
-#ifndef WAV_DECODER_H_
-#define WAV_DECODER_H_
+#pragma once
 
 #include <cstdint>
 #include <string>
@@ -29,6 +28,7 @@
  * (optional RIFF chunks)
  * */
 
+namespace esp_audio_libs {
 namespace wav_decoder {
 
 enum WAVDecoderState {
@@ -91,5 +91,4 @@ class WAVDecoder {
   uint16_t bits_per_sample_ = 0;
 };
 }  // namespace wav_decoder
-
-#endif  // WAV_DECODER_H_
+}  // namespace esp_audio_libs

src/decode/flac_decoder.cpp

@@ -6,6 +6,7 @@
 #include <esp_heap_caps.h>
 #include "flac_decoder.h"
 
+namespace esp_audio_libs {
 namespace flac {
 
 FLACDecoderResult FLACDecoder::read_header(uint8_t *buffer, size_t buffer_length) {
@@ -241,7 +242,8 @@ FLACDecoderResult FLACDecoder::decode_frame_header_() {
   return FLAC_DECODER_SUCCESS;
 }
 
-FLACDecoderResult FLACDecoder::decode_frame(uint8_t *buffer, size_t buffer_length, int16_t *output_buffer, uint32_t *num_samples) {
+FLACDecoderResult FLACDecoder::decode_frame(uint8_t *buffer, size_t buffer_length, int16_t *output_buffer,
+                                            uint32_t *num_samples) {
   this->buffer_ = buffer;
   this->buffer_index_ = 0;
   this->bytes_left_ = buffer_length;
@@ -606,3 +608,4 @@ int64_t FLACDecoder::read_rice_sint(uint8_t param) {
 void FLACDecoder::align_to_byte() { this->bit_buffer_length_ -= (this->bit_buffer_length_ % 8); }  // align_to_byte
 
 }  // namespace flac
+}  // namespace esp_audio_libs

src/decode/mp3_decoder.cpp

@@ -43,7 +43,9 @@
 #include "mp3_decoder.h"
 
 #include <esp_heap_caps.h>
-// #include "esphome/core/helpers.h"
+
+namespace esp_audio_libs {
+namespace helix_decoder {
 
 /* indexing = [version][samplerate index]
  * sample rate of frame (Hz)
@@ -8851,3 +8853,5 @@ int MP3Decode(HMP3Decoder hMP3Decoder, unsigned char **inbuf, int *bytesLeft, sh
   }
   return ERR_MP3_NONE;
 }
+}  // namespace helix_decoder
+}  // namespace esp_audio_libs