"undf" is making my VLC useless! Need help for a Mac (Panther)


Okay, Im sure that something similar has been discussed several times already, but I couldn’t find the exact thread, so I’m making a new one.

For years, I used to keepvid to download YouTube (and other videos) as .flv files to my Mac (which runs OS X 10.3.9, btw), where I would use VLC to play them. But a couple of months ago (after YouTube’s latest revamp) keepvid stopped supporting my downloads, and when I downloaded vids by using Safari, I got that “fourcc 'undf' " error that prevented anything from playing. Very annoying. How do I get around this?

(OT: for some reason, Safari crashes when I go to YouTube these days. Weird, it’s one of their supported browsers.)

Help! Thanks in advance. reply

I’ve had a few of those in the past too. I’m not sure what 'undf' audio stands for.*
I’ve found (on Windows) that both VLC and Media Player Classic - Home Cinema can’t play such files.
However Wimpy’s flv player (freeware) can handle such files fine.
There’s a version for the Mac, so I suggest you give it a try (though I can’t vouch for the results since I don’t own a Mac).
Feel free to report your results.

* here are just personal anecdotes: mediainfo in one sample says ADPCM audio, but on some forums i’ve seen voxware metasound mentioned; the former should be supported in VLC, but perhaps it’s packaged differently in flv? (if I recall, mu-law audio is packaged differently in mov files, which is why WMP can’t play it in mov files, but can in avi files) reply

7 people found this useful

Tried it and can confirm it works. reply


Uninstall VLC and revert to an older version, like 1.0.3:

http://download.videolan.org/pub/videolan/vlc/ reply

8 people found this useful

undf is just a format posted by VLC player when it cant define the type of media

it works fine on this player ! reply

5 people found this useful

hi i have seen aot of these questions all around, i have had the problem myself, so ive tweeked alot with the fraps to see what there would help, and now i got the solution! i hope so :P it worked for me, so here it is: where you choose to record audio, you may have turned “capture sound settings” to “multichannel”... TURN IT BACK TO STEREO!!! that helped for me :) hope you got it working now reply


Hey guys. I know this thread is pretty old. But in response to the initial post, you can use the activity window within Safari to download video files, and thus don’t need an external app. Read: http://www.usingmac.com/2008/5/30/free-download-youtube-video-with-safari reply

9 people found this useful

The GStreamer plugins fix this, at least on Arch Linux. Try them for your OS. reply


byanou reply




Found a solution that works for me. Elmedia Player for the Mac.

http://download.cnet.com/Elmedia-Player/3000-13632_4-75985205.html reply

15 people found this useful

Thank you for your help Macavity. The solution (Elmedia Player for the Mac) worked for me. reply


Thanks Kindly Macavity. Your help is invaluable. reply


I use wondershare, it has a free download and it says you need to purchase to convert the full video, but there is a preview button that you can press watch the full video.
http://www.wondershare.com/pro/mac-video-converter.html reply


Macavity’s solution is the first one that I’ve found for some problematic .mkv files. Thanks! reply


Also seems to have been updated in the latest version. Tried 2.2.1. :O reply


thank you Coinhunter reply


Elmedia Player rocks!
Thanks Macavity!!!! reply


I Love you the “Macavity” you’ve made my day.
Elmedia works very well on the undf!! reply



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