mp3 file --> I2S

[eismeraldo]

For testing purposes, I'm looking for a simple solution to output an mp3 stream to i2s. I used the example arduino-libhelix\examples\output_mp3\output_mp3.ino as a basis. But how can the dataCallback be used to send the audio data to I2S? Many thanks for any advice.

[pschatzmann]

You just call i2s.write(data, len);
Please note that the len must be specified is in bytes! and i2s must be declared and started properly before.

However I recommend you use the AudioTools, where you can just copy the data from the source to the target.

[eismeraldo]

This is exactly what I was looking for. Only an assert is thrown.
The code

#include "AudioTools.h"
#include "AudioTools/AudioCodecs/CodecMP3Helix.h"
#include "BabyElephantWalk60_mp3.h"

MemoryStream       data(BabyElephantWalk60_mp3, BabyElephantWalk60_mp3_len); // MP3 data source
MP3DecoderHelix    mp3;
EncodedAudioStream dec(&data, &mp3); // Decoding stream
I2SStream          i2s;              // final output of decoded stream
StreamCopy         copier(i2s, dec); // copy dec to out

void setup() {
    Serial.begin(115200);

    auto cfg = i2s.defaultConfig();
    cfg.pin_bck = 4;
    cfg.pin_ws = 6;
    cfg.pin_data = 5;

    i2s.begin(cfg);
    dec.begin();
}

void loop() {
    if (mp3) { copier.copy(); }
}

The error:
assert failed: void libhelix::MP3DecoderHelix::provideResult(MP3FrameInfo&) MP3DecoderHelix.h:155 (written == toWrite)
It seems that written != toWrite , what does that mean and how can I fix the error?

[pschatzmann]

The mp3 decoder expects that is can write all the data to the output. I guess some buffer is defined too small.
It is better (and more efficient) to do the decoding on the output side:

MemoryStream       data(BabyElephantWalk60_mp3, BabyElephantWalk60_mp3_len); // MP3 data source
MP3DecoderHelix    mp3;
I2SStream          i2s;              // final output of decoded stream
EncodedAudioStream dec(&i2s, &mp3); // Decoding stream
StreamCopy         copier(dec, data); // copy dec to out

[eismeraldo]

Perfect, thank you for the help