Issue with audio.h in esp32

I’m just exploring how I can store short sentence response I got from https://texttospeech.googleapis.com/v1/text:synthesize such as saving it as mp3 encoded or decoded. But when I tried to read from SPIFFS and play the audio, nothing gets played.

obj = JSON.parse(payload);
mp3Value = obj["audioContent"];
char buffer[sizeof(mp3Value)];
memcpy(buffer, &mp3Value, sizeof(mp3Value));
unsigned char * decoded = base64_decode((const unsigned char *)buffer, sizeof(buffer), &outputLength);
Serial.println(buffer);

// file.println(mp3Value);
file.write((uint8_t *)decoded, sizeof(decoded));
file.close();