Trouble setting volume dynamically

[EpiEndless]

Hi,
I have just started using arduino-audio-tools with ESP32 DevkitC - thanks for providing this great library.

The following code started as the streams-sd_mp3-i2s.ino example, modified to use SPIFFS instead of SD card, and to add volume control. An initial mp3 is played, and then in the loop(), a further mp3 is played 5 times as expected, all at the requested volume.

However, if I uncomment the "setVolume()" command in the loop, the ESP32 reboots after this message:
assert failed: T& audio_tools::Vector::operator [with T = float] Vector.h:257 (index < len)

Apparently I don't know how to change the volume dynamically.
Can anyone put me on the correct track here, please?

#define FORMAT_SPIFFS_IF_FAILED false

#include "FS.h"
#include "SPIFFS.h"
#include "AudioTools.h"
#include "AudioTools/AudioCodecs/CodecMP3Helix.h"

const int chipSelect=10;
I2SStream i2s; // final output of decoded stream
VolumeStream volume(i2s);
EncodedAudioStream decoder(&volume, new MP3DecoderHelix()); // Decoding stream
StreamCopy copier;
File audioFile;

int vol;

void setup(){
Serial.begin(115200);
AudioToolsLogger.begin(Serial, AudioToolsLogLevel::Warning);

// setup file
Serial.begin(115200);
if (!SPIFFS.begin(FORMAT_SPIFFS_IF_FAILED)) {
Serial.println("SPIFFS Mount Failed");
return;
}

audioFile = SPIFFS.open("/02 Garage door.mp3");

// setup i2s
auto config = i2s.defaultConfig(TX_MODE);
i2s.begin(config);

// set initial volume
auto vcfg = volume.defaultConfig();
vcfg.copyFrom(config);
//vcfg.allow_boost = true; // activate amplification using linear control
volume.begin(vcfg); // we need to provide the bits_per_sample and channels
volume.setVolume(1.0);

// setup I2S based on sampling rate provided by decoder
decoder.begin();

// begin copy
copier.begin(decoder, audioFile);

vol = 2;
}

void loop(){
if (!copier.copy()) {
if(vol > 10) stop();
else{
delay(200);
//volume.setVolume(0.5);
vol+=2;
audioFile.close();
audioFile = SPIFFS.open("/01 startup.mp3");
copier.begin(decoder, audioFile);
}
}
}

[pschatzmann]

Use the log level info (or debug) to figure out what is happening...
Provide the backtrace to find out what code path is causing this.

Somehow you access a vector at a position that does not exist. Maybe this is related to a changing number of channels ?

ps. I committed a correction, but I am not sure if it covers your special case w/o having further details...