Rated 5 out of 5 stars

you can even edit vedio's info by it!
but it can't download mp3... I've setup "YoutubeMP3Podcaster-Windows-3.0.2.xpi". it still showing a message: "Unicode file path detected, Download failed. Please go to Tools->Options->YoutubeMP3Podcaster->Troubleshooting, enable default location for temporary files, and set it to a folder with only letters a-z, A-Z or numbers 0-9"
 
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I got it! coz I didn't find the folder!
  (1) open the menu bar.
  (2) "Tools->YoutubeMP3Podcaster->Options" NOT "Tools->Options->YoutubeMP3Podcaster"
thanks for answer! I've solve this problem. :)

This review is for a previous version of the add-on (2.8.9.1-signed). 

Hi, this is a limitation of Firefox :). Firefox needs ffmpeg to make the mp3, and when YoutubeMP3Podcaster calls out to ffmpeg it can't find the original video to make the MP3 with if the path to the file has unicode.

As the pop up mentions there is a work around. Under Tools -> Options -> outubeMP3Podcaster->Troubleshooting you can set a temporary folder to save the MP3 to. Put a check mark in the box and make sure the path to the folder has only ASCII (a-z, A-Z or 0-9) in the box next to the checkmark.

Sorry for the inconvenience. I'm still trying to find a better solution, but it's tough because of how file system security works :(.