ERROR: audio conversion failed: Error opening filters!

[ghost]

How can I solve it? Thx

[debug] System config: []
[debug] User config: []
[debug] Command-line args: [u'--rm-cache-dir', u'--no-cache-dir', u'-o', u'/root/%(id)s.%(ext)s', u'https://www.youtube.com/watch?v=SAWl2DNx1lE', u'--extract-audio', u'--audio-format', u'mp3', u'--verbose']
[debug] Encodings: locale UTF-8, fs UTF-8, out UTF-8, pref UTF-8
[debug] youtube-dl version 2015.09.09
[debug] Python version 2.6.6 - Linux-2.6.32-504.30.3.el6.x86_64-x86_64-with-centos-6.6-Final
[debug] exe versions: ffmpeg 2.2.1, ffprobe 2.2.1
[debug] Proxy map: {}
Cache is disabled (Did you combine --no-cache-dir and --rm-cache-dir?)
[youtube] SAWl2DNx1lE: Downloading webpage
[youtube] SAWl2DNx1lE: Downloading video info webpage
[youtube] SAWl2DNx1lE: Extracting video information
[youtube] SAWl2DNx1lE: Downloading DASH manifest
[youtube] SAWl2DNx1lE: Downloading DASH manifest
[debug] Invoking downloader on u'https://r11---sn-25ge7ned.googlevideo.com/videoplayback?ipbits=0&pl=20&clen=3221813&requiressl=yes&mime=audio%2Fwebm&expire=1442296150&sparams=clen%2Cdur%2Cgir%2Cid%2Cinitcwndbps%2Cip%2Cipbits%2Citag%2Ckeepalive%2Clmt%2Cmime%2Cmm%2Cmn%2Cms%2Cmv%2Cpl%2Crequiressl%2Csource%2Cupn%2Cexpire&initcwndbps=3071250&mm=31&signature=3408372619423648922DEE8F4001E36F92E0C09D.1E0E594C94091C9DADE0B9B85A9621BDEA597895&mn=sn-25ge7ned&key=yt5&ip=MY_SERVER_IP&dur=208.581&keepalive=yes&sver=3&source=youtube&lmt=1441886775033146&id=o-AMqcuG8rGCcScBj31nfiTEwWMC-MU6soIV1ceYkzWt-F&ms=au&mt=1442274514&mv=m&fexp=9406990%2C9408710%2C9409069%2C9415365%2C9415485%2C9416023%2C9416126%2C9417707%2C9418153%2C9418448%2C9420348&upn=Cfe9cpW3MZ4&itag=251&gir=yes&ratebypass=yes'
[download] /root/SAWl2DNx1lE.webm has already been downloaded
[download] 100% of 3.07MiB
[debug] ffmpeg command line: ffprobe -show_streams /root/SAWl2DNx1lE.webm
[ffmpeg] Destination: /root/SAWl2DNx1lE.mp3
[debug] ffmpeg command line: ffmpeg -y -i /root/SAWl2DNx1lE.webm -vn -acodec libmp3lame -q:a 5 /root/SAWl2DNx1lE.mp3
ERROR: audio conversion failed: Error opening filters!
Traceback (most recent call last):
  File "/usr/local/bin/youtube-dl/youtube_dl/YoutubeDL.py", line 1704, in post_process
    files_to_delete, info = pp.run(info)
  File "/usr/local/bin/youtube-dl/youtube_dl/postprocessor/ffmpeg.py", line 276, in run
    'audio conversion failed: ' + e.msg)
PostProcessingError

[dstftw]

Update ffmpeg.

[mrkapqa]

deleted

[mrkapqa]

i am compiling missing libraries for ffmpeg, eg libmp3lame, libx264, hopefully enables it. i want to use ffmpeg, thanks