Finds low quality songs in a directory based on a minimum bit rate. Tested with PHP 5.5.4. Find MediaInfo at mediaarea.net. I don't rely on MediaInfo for the recursion because it uses a fuckton of memory trying to do it.

findLowQualitySongs.php

<?php
/*******************************************************************************
 *  Copyright 2013 Kevin Mark                                                  *
 *                                                                             *
 *  Licensed under the Apache License, Version 2.0 (the "License");            *
 *  you may not use this file except in compliance with the License.           *
 *  You may obtain a copy of the License at                                    *
 *                                                                             *
 *      http://www.apache.org/licenses/LICENSE-2.0                             *
 *                                                                             *
 *  Unless required by applicable law or agreed to in writing, software        *
 *  distributed under the License is distributed on an "AS IS" BASIS,          *
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.   *
 *  See the License for the specific language governing permissions and        *
 *  limitations under the License.                                             *
 *******************************************************************************/

// Finds low quality songs in a directory based on a minimum bit rate
// Tested with PHP 5.5.4
// MediaInfo -> mediaarea.net
// I don't rely on MediaInfo for the recursion because it uses a fuckton of memory trying to do it.

// Directory to search
$directory = "/Users/kmark/Music/iTunes/iTunes Media/Music";

// Minimum overall bit rate in Kbps
$minQuality = 256;

// Path to mediainfo
$mediainfo = "/usr/local/bin/mediainfo";

// Shorten output?
$doShortenPath = true;

// If MP3 and LAME-encoded ignore bit rate on files that match this encoding settings regex
// Set null to disable
$lameIgnore = '/-V ?0/i'; // Skips -V 0 files

// If MP3 and LAME-encoded AND it fails the above check output the encoding settings too
$outEncSettings = true;

error_reporting(E_ALL ^ E_NOTICE);

if(!file_exists($directory) && !is_readable($directory)) {
	exit("Cannot read from $directory\r\n");
}

$recursiveDirectory = new RecursiveIteratorIterator(new RecursiveDirectoryIterator($directory, FilesystemIterator::SKIP_DOTS));
$RegexIterator = new RegexIterator($recursiveDirectory, '/^.+\.(?:mp4|m4a|aac|mp3|aiff|wav)$/i', RecursiveRegexIterator::GET_MATCH);

foreach($RegexIterator as $path) {
	$path = $path[0];
	// May have problems if $mediainfo or $path includes quotes
	$output = shell_exec("\"$mediainfo\" \"$path\"");
	if($output == null) {
		exit("MediaInfo shell_exec failed on $path\r\n");
	}
	if(preg_match('/^Overall bit rate +: ([\d.]+ Kbps)/im', $output, $bitrate)) {
		$bitrate = (int)$bitrate[1];
		if($bitrate < $minQuality) {
			if($lameIgnore != null) {
				if(preg_match('/^Encoding settings +: (-.+)$/im', $output, $encodingSettings)) {
					if(preg_match($lameIgnore, $encodingSettings[1])) {
						continue;
					}
				}
			}
			echo "$bitrate Kbps : " . shortenPath($path) .
				(isset($encodingSettings[1]) && $outEncSettings ? (" [".$encodingSettings[1]."]") : ("")) . "\r\n";
		}
		continue;
	}
	// Uncomment this if you're concerned. Bit rate probably displayed in Mbps or not shown at all
	//exit("Mediainfo regex parsing failed on $path\r\n");
}

function shortenPath($fullpath) {
	if(!$GLOBALS["doShortenPath"]) {
		return $fullpath;
	}
	// Crude but effective
	return substr($fullpath, strlen($GLOBALS["directory"]) + 1);
}