diff -r 490d5cc509ed -r cf61fcea0001 wp/wp-includes/ID3/module.tag.id3v1.php
--- a/wp/wp-includes/ID3/module.tag.id3v1.php	Tue Jun 09 11:14:17 2015 +0000
+++ b/wp/wp-includes/ID3/module.tag.id3v1.php	Mon Oct 14 17:39:30 2019 +0200
@@ -22,7 +22,7 @@
 		$info = &$this->getid3->info;
 
 		if (!getid3_lib::intValueSupported($info['filesize'])) {
-			$info['warning'][] = 'Unable to check for ID3v1 because file is larger than '.round(PHP_INT_MAX / 1073741824).'GB';
+			$this->warning('Unable to check for ID3v1 because file is larger than '.round(PHP_INT_MAX / 1073741824).'GB');
 			return false;
 		}
 
@@ -60,6 +60,26 @@
 			foreach ($ParsedID3v1 as $key => $value) {
 				$ParsedID3v1['comments'][$key][0] = $value;
 			}
+			// ID3v1 encoding detection hack START
+			// ID3v1 is defined as always using ISO-8859-1 encoding, but it is not uncommon to find files tagged with ID3v1 using Windows-1251 or other character sets
+			// Since ID3v1 has no concept of character sets there is no certain way to know we have the correct non-ISO-8859-1 character set, but we can guess
+			$ID3v1encoding = 'ISO-8859-1';
+			foreach ($ParsedID3v1['comments'] as $tag_key => $valuearray) {
+				foreach ($valuearray as $key => $value) {
+					if (preg_match('#^[\\x00-\\x40\\xA8\\B8\\x80-\\xFF]+$#', $value)) {
+						foreach (array('Windows-1251', 'KOI8-R') as $id3v1_bad_encoding) {
+							if (function_exists('mb_convert_encoding') && @mb_convert_encoding($value, $id3v1_bad_encoding, $id3v1_bad_encoding) === $value) {
+								$ID3v1encoding = $id3v1_bad_encoding;
+								break 3;
+							} elseif (function_exists('iconv') && @iconv($id3v1_bad_encoding, $id3v1_bad_encoding, $value) === $value) {
+								$ID3v1encoding = $id3v1_bad_encoding;
+								break 3;
+							}
+						}
+					}
+				}
+			}
+			// ID3v1 encoding detection hack END
 
 			// ID3v1 data is supposed to be padded with NULL characters, but some taggers pad with spaces
 			$GoodFormatID3v1tag = $this->GenerateID3v1Tag(
@@ -73,13 +93,14 @@
 			$ParsedID3v1['padding_valid'] = true;
 			if ($id3v1tag !== $GoodFormatID3v1tag) {
 				$ParsedID3v1['padding_valid'] = false;
-				$info['warning'][] = 'Some ID3v1 fields do not use NULL characters for padding';
+				$this->warning('Some ID3v1 fields do not use NULL characters for padding');
 			}
 
 			$ParsedID3v1['tag_offset_end']   = $info['filesize'];
 			$ParsedID3v1['tag_offset_start'] = $ParsedID3v1['tag_offset_end'] - 128;
 
 			$info['id3v1'] = $ParsedID3v1;
+			$info['id3v1']['encoding'] = $ID3v1encoding;
 		}
 
 		if (substr($preid3v1, 0, 3) == 'TAG') {
@@ -95,7 +116,7 @@
 				// a Lyrics3 tag footer was found before the last ID3v1, assume false "TAG" synch
 			} else {
 				// APE and Lyrics3 footers not found - assume double ID3v1
-				$info['warning'][] = 'Duplicate ID3v1 tag detected - this has been known to happen with iTunes';
+				$this->warning('Duplicate ID3v1 tag detected - this has been known to happen with iTunes');
 				$info['avdataend'] -= 128;
 			}
 		}
@@ -357,4 +378,4 @@
 		return $ID3v1Tag;
 	}
 
-}
\ No newline at end of file
+}