AudioSynthWaveformSine_F32, stereo I2S output to DAC out-of-phase @ sample rate 44100 & 44117 Hz #21
Description
S/W: Windows 10, Arduino 1.8.19, Teensyduino 1.57, OpenAudio library up to and including commit 88126e2.
H/W: Teensy 3.2 plus PCM5102A DAC.
While playing with the OpenAudio library generating a sine wave, I noticed that for sample rates 44100 & 44117 Hz, the sine output is out-of-phase.
Here is the code used:
#include "OpenAudio_ArduinoLibrary.h"
#include "AudioStream_F32.h"
#include <Audio.h>
// T3.x supported sample rates: 2000, 8000, 11025, 16000, 22050, 24000, 32000, 44100, 44117, 48000,
// 88200, 88235 (44117*2), 95680, 96000, 176400, 176470, 192000
// T4.x supports any sample rate the codec will handle.
const float sample_rate_Hz = 32000,0f;
const float freq = 1000.0f;
const int audio_block_samples = 128;
AudioSettings_F32 audio_settings(sample_rate_Hz, audio_block_samples);
AudioSynthWaveformSine_F32 sine1(audio_settings);
AudioOutputI2S_F32 audioOutI2S1(audio_settings);
AudioConnection_F32 patchCord1(sine1, 0, audioOutI2S1, 0);
AudioConnection_F32 patchCord2(sine1, 0, audioOutI2S1, 1);
void setup() {
AudioMemory(20);
AudioMemory_F32(20);
sine1.amplitude(1.0);
sine1.frequency(freq);
sine1.begin();
}
void loop() {
}
Output on scope at SR = 32000 Hz:
Output on scope at SR = 44100 Hz:
Output on scope at SR = 44117 Hz:
Output on scope at SR = 48000 Hz:
The logic analyzer on the I2S signals also shows different L&R samples at 44100 & 44117 Hz.
Paul