wgetとavconvでYouTube URLをM4A (AAC) ファイルに変換

gistfile1.txt

$ python yt2m4a.py "http://www.youtube.com/watch?v=4YMD6xELI_k"
--2014-04-11 02:25:26--  http://r2---sn-ogueyn7z.googlevideo.com/videoplayback?sparams=id%2Cip%2Cipbits%2Citag%2Cpcm2fr%2Cratebypass%2Csource%2Cupn%2Cexpire&ipbits=0&mt=1397150542&expire=1397173854&upn=15FckWnBsJw&fexp=927905%2C936905%2C901065%2C916623%2C945513%2C937417%2C913434%2C936916%2C934022%2C936921%2C936923&signature=A2B6A3A92CCB9F6F09EDEC21266137C2A09975DF.A94CC65958FD475F79CE18DDF05188C29591C7A0&key=yt5&ip=123.224.99.3&pcm2fr=yes&itag=22&source=youtube&sver=3&mv=u&ratebypass=yes&ms=au&id=o-ADTX4MBPHtBDylBsjOsDle1msEAsW4PTJ7EyQH0qyPo1
Resolving r2---sn-ogueyn7z.googlevideo.com (r2---sn-ogueyn7z.googlevideo.com)... 74.125.171.39
Connecting to r2---sn-ogueyn7z.googlevideo.com (r2---sn-ogueyn7z.googlevideo.com)|74.125.171.39|:80... connected.
HTTP request sent, awaiting response... 302 Found
Location: http://r13---sn-ogueyn7z.googlevideo.com/videoplayback?sparams=id%2Cip%2Cipbits%2Citag%2Cpcm2fr%2Cratebypass%2Csource%2Cupn%2Cexpire&ipbits=0&mt=1397150542&expire=1397173854&upn=15FckWnBsJw&fexp=927905%2C936905%2C901065%2C916623%2C945513%2C937417%2C913434%2C936916%2C934022%2C936921%2C936923&signature=A2B6A3A92CCB9F6F09EDEC21266137C2A09975DF.A94CC65958FD475F79CE18DDF05188C29591C7A0&
key=yt5&ip=123.224.99.3&pcm2fr=yes&itag=22&source=youtube&sver=3&mv=u&ratebypass=yes&ms=au&id=o-ADTX4MBPHtBDylBsjOsDle1msEAsW4PTJ7EyQH0qyPo1&ir=1&rr=12 [following]
--2014-04-11 02:25:27--  http://r13---sn-ogueyn7z.googlevideo.com/videoplayback?sparams=id%2Cip%2Cipbits%2Citag%2Cpcm2fr%2Cratebypass%2Csource%2Cupn%2Cexpire&ipbits=0&mt=1397150542&expire=1397173854&upn=15FckWnBsJw&fexp=927905%2C936905%2C901065%2C916623%2C945513%2C937417%2C913434%2C936916%2C934022%2C936921%2C936923&signature=A2B6A3A92CCB9F6F09EDEC21266137C2A09975DF.A94CC65958FD475F79CE18DDF05188C29591C7A0&key=yt5&ip=123.224.99.3&pcm2fr=yes&itag=22&source=youtube&sver=3&mv=u&ratebypass=yes&ms=au&id=o-ADTX4MBPHtBDylBsjOsDle1msEAsW4PTJ7EyQH0qyPo1&ir=1&rr=12
Resolving r13---sn-ogueyn7z.googlevideo.com (r13---sn-ogueyn7z.googlevideo.com)... 74.125.171.50
Connecting to r13---sn-ogueyn7z.googlevideo.com (r13---sn-ogueyn7z.googlevideo.com)|74.125.171.50|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 41464901 (40M) [video/mp4]
Saving to: `Google Maps: Pokémon Challenge.mp4'

100%[===========================================================================================================================================================>] 41,464,901  7.21M/s   in 5.6s

2014-04-11 02:25:32 (7.06 MB/s) - `Google Maps: Pokémon Challenge.mp4' saved [41464901/41464901]

avconv version 0.8.10-4:0.8.10-0ubuntu0.12.04.1, Copyright (c) 2000-2013 the Libav developers
  built on Feb  6 2014 20:56:59 with gcc 4.6.3
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'Google Maps: Pokémon Challenge.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2014-03-28 21:36:51
  Duration: 00:02:33.41, start: 0.000000, bitrate: 2162 kb/s
    Stream #0.0(und): Video: h264 (High), yuv420p, 1280x720 [PAR 1:1 DAR 16:9], 1967 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc
    Stream #0.1(und): Audio: aac, 44100 Hz, stereo, s16, 191 kb/s
    Metadata:
      creation_time   : 2014-03-28 21:36:54
Output #0, ipod, to 'Google Maps: Pokémon Challenge.m4a':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2014-03-28 21:36:51
    encoder         : Lavf53.21.1
    Stream #0.0(und): Audio: aac, 44100 Hz, stereo, 191 kb/s
    Metadata:
      creation_time   : 2014-03-28 21:36:54
Stream mapping:
  Stream #0:1 -> #0:0 (copy)
Press ctrl-c to stop encoding
size=    3648kB time=153.41 bitrate= 194.8kbits/s
video:0kB audio:3596kB global headers:0kB muxing overhead 1.455482%

$ ls
Google Maps: Pokémon Challenge.m4a  Google Maps: Pokémon Challenge.mp4  yt2m4a.py

$ file Google*
Google Maps: Pokémon Challenge.m4a: ISO Media, MPEG v4 system, iTunes AAC-LC
Google Maps: Pokémon Challenge.mp4: ISO Media, MPEG v4 system, version 2

yt2m4a.py

import sys
import re
import urllib2
import urllib
import subprocess

def yt2m4a(url):
    f = urllib2.urlopen(url)
    html = f.read()
    f.close()

    if not html:
        raise Exception('error to get html')

    m = re.search(r'"title": "([^"]+)"', html)
    if m is None:
        raise Exception('error to get title')
    title = m.group(1).decode('unicode-escape')

    m = re.search(r'"url_encoded_fmt_stream_map": "([^"]+)"', html)
    if m is None:
        raise Exception('error to get url_encoded_fmt_stream_map')
    params = [x for x in m.group(1).split(',') if 'itag=22' in x] or [x for x in m.group(1).split(',') if 'itag=18' in x]
    if not params:
        raise Exception('error to get fmt=22 and fmt=18')
    m = re.search(r'url=(.+)\\u0026', params[0])
    if m is None:
        raise Exception('error to get video url')
    video_url = urllib.unquote(m.group(1))

    filename = title.replace('/', '_').replace('\x00', '_')
    subprocess.check_call(['wget', '-O', filename+'.mp4', video_url])
    subprocess.check_call(['avconv', '-i', filename+'.mp4', '-acodec', 'copy', '-vn', filename+'.m4a'])

if __name__ == '__main__':
    if len(sys.argv) < 2:
        print >>sys.stderr, "Usage: python %s URL" % sys.argv[0]
        sys.exit(1)
    url = sys.argv[1]
    yt2m4a(url)