aacgain.py

import os
import subprocess
import threading

from Queue import Queue

ITUNES_DIR = os.path.expanduser("~/Music/iTunes/iTunes Music/")
KNOWN_EXTENSIONS = ('.mp3', '.aac')
AACGAIN_PARAMS = ['-a', '-k', '-d', '3']
AACGAIN_LOCATION = 'aacgain'

def get_files():
    """
    A generator that returns tuples with album name and a list of mp3 files.
    """
    for root, dirs, files in os.walk(ITUNES_DIR):
        files = filter(lambda x: os.path.splitext(x)[1] in KNOWN_EXTENSIONS, files)
        if files:
            yield [os.path.join(root, f) for f in files]

def get_num_cpus():
    """
    Returns the number of cpus in the machine, and 1 on failure.
    """
    try:
        return int(subprocess.Popen(['sysctl', '-n', 'hw.ncpu'], stdout=subprocess.PIPE).communicate()[0].strip())
    except:
        return 1

def run_aacgain(queue):
    """
    Returns a callable that will be called inside a thread.
    """
    def callable():
        try:
            while True:
                files = queue.get()

                if files is None:
                    break

                p = subprocess.Popen([AACGAIN_LOCATION] + AACGAIN_PARAMS + files)
                p.wait()
        except KeyboardInterrupt:
            pass
    return callable

queue = Queue()
workers = []

for i in range(get_num_cpus()):
    worker = threading.Thread(target=run_aacgain(queue))
    worker.start()

    workers.append(worker)

for album_files in get_files():
    queue.put(album_files)

for i in range(get_num_cpus()):
    queue.put(None)