ESP32 play mp3

[utiq]

I just saw this video of this person who was able to play mp3 without a codec chip using an ESP32 module https://www.youtube.com/watch?v=kdKnddqCJbY it seems interesting and I wanted to include it in my project, the problem is that I'm not being able to decode a mp3 file.
He implemented it in Arduino

https://github.com/atomic14/esp32-play-mp3-demo
https://github.com/lieff/minimp3

I'm creating a C module to be able to implement the library, this is my code, it crashes in line 36. What am I doing wrong? 🤔

#include "py/obj.h"
#include "py/runtime.h"
#include "py/binary.h"

#define MINIMP3_IMPLEMENTATION
#include "minimp3.h"

STATIC mp_obj_t minimp3_decode(mp_obj_t mp3_data)
{
    // Initialize decoder
    static mp3dec_t mp3d;
    mp3dec_init(&mp3d);

    mp_buffer_info_t bufinfo;
    mp_get_buffer_raise(mp3_data, &bufinfo, MP_BUFFER_READ);

    // Validate the entire buffer once
    if (!bufinfo.buf || bufinfo.len <= 0)
    {
        mp_raise_ValueError("Invalid buffer or length in mp3 decoding");
        return mp_const_none;
    }

    // Setup buffer management variables
    size_t buffered = bufinfo.len;
    size_t to_read = buffered; // This represents the initial buffered amount
    const uint8_t *input_buf = bufinfo.buf;
    const uint8_t *read_ptr = input_buf; // Pointer to the current read position
    mp3dec_frame_info_t info;
    short pcm[MINIMP3_MAX_SAMPLES_PER_FRAME];
    int total_samples = 0;

    // Decode process
    while (to_read > 0)
    {
        int samples = mp3dec_decode_frame(&mp3d, read_ptr, buffered, pcm, &info);

        if (samples > 0)
        {
            // Process or store the decoded samples...
            total_samples += samples;

            // For simplicity, I'm just testing some frames from the mp3 file
        }

        if (info.frame_bytes > 0)
        {
            // Update buffer pointers and sizes
            read_ptr += info.frame_bytes;
            buffered -= info.frame_bytes;
            to_read -= info.frame_bytes;
        }
        else
        {
            // No more decodable data
            break;
        }
    }

    // Return the total number of samples decoded as a simple indicator, for testing purposes
    return mp_obj_new_int(total_samples);
}

MP_DEFINE_CONST_FUN_OBJ_1(minimp3_decode_obj, minimp3_decode);

// Define the module dictionary
STATIC const mp_rom_map_elem_t minimp3_module_globals_table[] = {
    {MP_ROM_QSTR(MP_QSTR_decode), MP_ROM_PTR(&minimp3_decode_obj)},
    // Add more functions if needed
};

STATIC MP_DEFINE_CONST_DICT(minimp3_module_globals, minimp3_module_globals_table);

// Define the module
const mp_obj_module_t minimp3_user_cmodule = {
    .base = {&mp_type_module},
    .globals = (mp_obj_dict_t *)&minimp3_module_globals,
};

// Register the module with MicroPython
MP_REGISTER_MODULE(MP_QSTR_minimp3, minimp3_user_cmodule);

[jimmo]

@utiq Unfortunately line 36 is the call to mp3dec_decode_frame so it would be helpful to know where in mp3dec_decode_frame it's crashing.

But just from a quick review, I'm nervous about the to_read variable being size_t, and therefore potentially being able to underflow when you do to_read -= info.frame_bytes ?

Either way... add some print-style debugging to the line before and verify that all the variables and points are what you expect. And also whether it's failing on the first iteration or later.

[MATTYGILO]

@utiq Did you find a solution in the end?

[utiq]

@MATTYGILO I'm using ESP-ADF

[MATTYGILO]

@utiq Thanks. Is it possible for you to share your Micropython C module? I would be incredibly grateful.