playMP3(fileName, timecode)

[JonGordon123]

Arduino 1.8.19 LilyPad MP3

I was having a few issues when attempting to play an mp3 from a specified ms time and found the following.

1. The variable "bitrate" is declared in SFEMP3Shield.h as a uint8_t, which only allows bitrates up to 224kbps. I changed it to uint16_t which solves that issue.

2. The If...else if... else if... else statement found in the getBitRateFromMP3File(filename) function (SFEMP3Shield.cpp) seems to not be functioning as, I imagine, it should be. If the MP3 file is MPEG Version 2/2.5 then the first if statement evaluates true, and no other code is run in the if/else if block.... causing the "bitrate" variable to be filled with an incorrect bitrate. I tested with multiple files, bitrates, and sample rates and was getting incorrect bitrates often.

 //found the 11 1's
  //parse version, layer and bitrate out and save bitrate
  if(!(temp & 0b00001000)) { //!true if Version 1, !false version 2 and 2.5
    row_num = 3;
  }
  else if((temp & 0b00000110) == 0b00000100) { //true if layer 2, false if layer 1 or 3
    row_num += 1;
  }
  else if((temp & 0b00000110) == 0b00000010) { //true if layer 3, false if layer 2 or 1
    row_num += 2;
  } else {
    continue; // Not found, need to skip the rest and continue looking.
              // \warning But this can lead to a dead end and file end of file.
  }

I seem to have fixed my issue by replacing the existing if...else if....else if...else with the following.

bool nobits = true;

if(!(temp & 0b00001000)) {
   // MPEG Version 2 or 2.5
   row_num = 3;
   nobits = false;
}
if((temp & 0b00000110) == 0b00000110) {
  // Layer 1
  //row_num += 0;
  nobits = false;
}
if((temp & 0b00000110) == 0b00000100) {
  // Layer 2
  row_num += 1;
  nobits = false;
}
if((temp & 0b00000110) == 0b00000010) {
  // Layer 3
  row_num += 2;
  nobits = false;
}
if(nobits){
  continue;
}

These two changes allowed me to play any file from any ms timestamp, without issue.