public function ParseVorbisComments()
 {
     $info =& $this->getid3->info;
     $OriginalOffset = $this->ftell();
     $commentdataoffset = 0;
     $VorbisCommentPage = 1;
     switch ($info['audio']['dataformat']) {
         case 'vorbis':
         case 'speex':
             $CommentStartOffset = $info['ogg']['pageheader'][$VorbisCommentPage]['page_start_offset'];
             // Second Ogg page, after header block
             $this->fseek($CommentStartOffset);
             $commentdataoffset = 27 + $info['ogg']['pageheader'][$VorbisCommentPage]['page_segments'];
             $commentdata = $this->fread(self::OggPageSegmentLength($info['ogg']['pageheader'][$VorbisCommentPage], 1) + $commentdataoffset);
             if ($info['audio']['dataformat'] == 'vorbis') {
                 $commentdataoffset += strlen('vorbis') + 1;
             }
             break;
         case 'flac':
             $CommentStartOffset = $info['flac']['VORBIS_COMMENT']['raw']['offset'] + 4;
             $this->fseek($CommentStartOffset);
             $commentdata = $this->fread($info['flac']['VORBIS_COMMENT']['raw']['block_length']);
             break;
         default:
             return false;
     }
     $VendorSize = getid3_lib::LittleEndian2Int(substr($commentdata, $commentdataoffset, 4));
     $commentdataoffset += 4;
     $info['ogg']['vendor'] = substr($commentdata, $commentdataoffset, $VendorSize);
     $commentdataoffset += $VendorSize;
     $CommentsCount = getid3_lib::LittleEndian2Int(substr($commentdata, $commentdataoffset, 4));
     $commentdataoffset += 4;
     $info['avdataoffset'] = $CommentStartOffset + $commentdataoffset;
     $basicfields = array('TITLE', 'ARTIST', 'ALBUM', 'TRACKNUMBER', 'GENRE', 'DATE', 'DESCRIPTION', 'COMMENT');
     $ThisFileInfo_ogg_comments_raw =& $info['ogg']['comments_raw'];
     for ($i = 0; $i < $CommentsCount; $i++) {
         $ThisFileInfo_ogg_comments_raw[$i]['dataoffset'] = $CommentStartOffset + $commentdataoffset;
         if ($this->ftell() < $ThisFileInfo_ogg_comments_raw[$i]['dataoffset'] + 4) {
             if ($oggpageinfo = $this->ParseOggPageHeader()) {
                 $info['ogg']['pageheader'][$oggpageinfo['page_seqno']] = $oggpageinfo;
                 $VorbisCommentPage++;
                 // First, save what we haven't read yet
                 $AsYetUnusedData = substr($commentdata, $commentdataoffset);
                 // Then take that data off the end
                 $commentdata = substr($commentdata, 0, $commentdataoffset);
                 // Add [headerlength] bytes of dummy data for the Ogg Page Header, just to keep absolute offsets correct
                 $commentdata .= str_repeat("", 27 + $info['ogg']['pageheader'][$oggpageinfo['page_seqno']]['page_segments']);
                 $commentdataoffset += 27 + $info['ogg']['pageheader'][$oggpageinfo['page_seqno']]['page_segments'];
                 // Finally, stick the unused data back on the end
                 $commentdata .= $AsYetUnusedData;
                 //$commentdata .= $this->fread($info['ogg']['pageheader'][$oggpageinfo['page_seqno']]['page_length']);
                 $commentdata .= $this->fread($this->OggPageSegmentLength($info['ogg']['pageheader'][$VorbisCommentPage], 1));
             }
         }
         $ThisFileInfo_ogg_comments_raw[$i]['size'] = getid3_lib::LittleEndian2Int(substr($commentdata, $commentdataoffset, 4));
         // replace avdataoffset with position just after the last vorbiscomment
         $info['avdataoffset'] = $ThisFileInfo_ogg_comments_raw[$i]['dataoffset'] + $ThisFileInfo_ogg_comments_raw[$i]['size'] + 4;
         $commentdataoffset += 4;
         while (strlen($commentdata) - $commentdataoffset < $ThisFileInfo_ogg_comments_raw[$i]['size']) {
             if ($ThisFileInfo_ogg_comments_raw[$i]['size'] > $info['avdataend'] || $ThisFileInfo_ogg_comments_raw[$i]['size'] < 0) {
                 $info['warning'][] = 'Invalid Ogg comment size (comment #' . $i . ', claims to be ' . number_format($ThisFileInfo_ogg_comments_raw[$i]['size']) . ' bytes) - aborting reading comments';
                 break 2;
             }
             $VorbisCommentPage++;
             $oggpageinfo = $this->ParseOggPageHeader();
             $info['ogg']['pageheader'][$oggpageinfo['page_seqno']] = $oggpageinfo;
             // First, save what we haven't read yet
             $AsYetUnusedData = substr($commentdata, $commentdataoffset);
             // Then take that data off the end
             $commentdata = substr($commentdata, 0, $commentdataoffset);
             // Add [headerlength] bytes of dummy data for the Ogg Page Header, just to keep absolute offsets correct
             $commentdata .= str_repeat("", 27 + $info['ogg']['pageheader'][$oggpageinfo['page_seqno']]['page_segments']);
             $commentdataoffset += 27 + $info['ogg']['pageheader'][$oggpageinfo['page_seqno']]['page_segments'];
             // Finally, stick the unused data back on the end
             $commentdata .= $AsYetUnusedData;
             //$commentdata .= $this->fread($info['ogg']['pageheader'][$oggpageinfo['page_seqno']]['page_length']);
             if (!isset($info['ogg']['pageheader'][$VorbisCommentPage])) {
                 $info['warning'][] = 'undefined Vorbis Comment page "' . $VorbisCommentPage . '" at offset ' . $this->ftell();
                 break;
             }
             $readlength = self::OggPageSegmentLength($info['ogg']['pageheader'][$VorbisCommentPage], 1);
             if ($readlength <= 0) {
                 $info['warning'][] = 'invalid length Vorbis Comment page "' . $VorbisCommentPage . '" at offset ' . $this->ftell();
                 break;
             }
             $commentdata .= $this->fread($readlength);
             //$filebaseoffset += $oggpageinfo['header_end_offset'] - $oggpageinfo['page_start_offset'];
         }
         $ThisFileInfo_ogg_comments_raw[$i]['offset'] = $commentdataoffset;
         $commentstring = substr($commentdata, $commentdataoffset, $ThisFileInfo_ogg_comments_raw[$i]['size']);
         $commentdataoffset += $ThisFileInfo_ogg_comments_raw[$i]['size'];
         if (!$commentstring) {
             // no comment?
             $info['warning'][] = 'Blank Ogg comment [' . $i . ']';
         } elseif (strstr($commentstring, '=')) {
             $commentexploded = explode('=', $commentstring, 2);
             $ThisFileInfo_ogg_comments_raw[$i]['key'] = strtoupper($commentexploded[0]);
             $ThisFileInfo_ogg_comments_raw[$i]['value'] = isset($commentexploded[1]) ? $commentexploded[1] : '';
             if ($ThisFileInfo_ogg_comments_raw[$i]['key'] == 'METADATA_BLOCK_PICTURE') {
                 // http://wiki.xiph.org/VorbisComment#METADATA_BLOCK_PICTURE
                 // The unencoded format is that of the FLAC picture block. The fields are stored in big endian order as in FLAC, picture data is stored according to the relevant standard.
                 // http://flac.sourceforge.net/format.html#metadata_block_picture
                 $flac = new getid3_flac($this->getid3);
                 $flac->setStringMode(base64_decode($ThisFileInfo_ogg_comments_raw[$i]['value']));
                 $flac->parsePICTURE();
                 $info['ogg']['comments']['picture'][] = $flac->getid3->info['flac']['PICTURE'][0];
                 unset($flac);
             } elseif ($ThisFileInfo_ogg_comments_raw[$i]['key'] == 'COVERART') {
                 $data = base64_decode($ThisFileInfo_ogg_comments_raw[$i]['value']);
                 $this->notice('Found deprecated COVERART tag, it should be replaced in honor of METADATA_BLOCK_PICTURE structure');
                 /** @todo use 'coverartmime' where available */
                 $imageinfo = getid3_lib::GetDataImageSize($data);
                 if ($imageinfo === false || !isset($imageinfo['mime'])) {
                     $this->warning('COVERART vorbiscomment tag contains invalid image');
                     continue;
                 }
                 $ogg = new self($this->getid3);
                 $ogg->setStringMode($data);
                 $info['ogg']['comments']['picture'][] = array('image_mime' => $imageinfo['mime'], 'data' => $ogg->saveAttachment('coverart', 0, strlen($data), $imageinfo['mime']));
                 unset($ogg);
             } else {
                 $info['ogg']['comments'][strtolower($ThisFileInfo_ogg_comments_raw[$i]['key'])][] = $ThisFileInfo_ogg_comments_raw[$i]['value'];
             }
         } else {
             $info['warning'][] = '[known problem with CDex >= v1.40, < v1.50b7] Invalid Ogg comment name/value pair [' . $i . ']: ' . $commentstring;
         }
         unset($ThisFileInfo_ogg_comments_raw[$i]);
     }
     unset($ThisFileInfo_ogg_comments_raw);
     // Replay Gain Adjustment
     // http://privatewww.essex.ac.uk/~djmrob/replaygain/
     if (isset($info['ogg']['comments']) && is_array($info['ogg']['comments'])) {
         foreach ($info['ogg']['comments'] as $index => $commentvalue) {
             switch ($index) {
                 case 'rg_audiophile':
                 case 'replaygain_album_gain':
                     $info['replay_gain']['album']['adjustment'] = (double) $commentvalue[0];
                     unset($info['ogg']['comments'][$index]);
                     break;
                 case 'rg_radio':
                 case 'replaygain_track_gain':
                     $info['replay_gain']['track']['adjustment'] = (double) $commentvalue[0];
                     unset($info['ogg']['comments'][$index]);
                     break;
                 case 'replaygain_album_peak':
                     $info['replay_gain']['album']['peak'] = (double) $commentvalue[0];
                     unset($info['ogg']['comments'][$index]);
                     break;
                 case 'rg_peak':
                 case 'replaygain_track_peak':
                     $info['replay_gain']['track']['peak'] = (double) $commentvalue[0];
                     unset($info['ogg']['comments'][$index]);
                     break;
                 case 'replaygain_reference_loudness':
                     $info['replay_gain']['reference_volume'] = (double) $commentvalue[0];
                     unset($info['ogg']['comments'][$index]);
                     break;
                 default:
                     // do nothing
                     break;
             }
         }
     }
     $this->fseek($OriginalOffset);
     return true;
 }