problems using ffmpeg

[IAMTubby]

Hi,
I am trying to {download an mp3 file from youtube} OR {download a video and then convert it to mp3}. I'm unable to do both probably because of ffmpeg.
I have tried the following so far


1. youtube-dl -o ubuntu.flv http://www.youtube.com/watch?v=LoXpLUr5WB4 --audio-format=mp3
strange, but gives me only the flv


2. Tried without the = also as
youtube-dl -o ubuntu.flv http://www.youtube.com/watch?v=LoXpLUr5WB4 --audio-format mp3
again, only downloaded the flv


3. Tried first downloading the flv/mp4 and then converting to audio. as
ffmpeg -i filename.flv filename.mp3
This does generate a file called filename.mp3 , but of size 0. Please find attached the log file of ffmpeg

And this is the ls output of my audio file
-rw-rw-r-- 1 IAMTubby IAMTubby 0 2013-03-23 08:18 myaudio.mp3

4.I also went to this link http://ubuntuforums.org/showthread.php?t=1084538&p=8370224#post8370224 where OP was facing similar problem . His solution was to do sudo apt-get install libavcodec-unstripped-52 . I did the same but it gives me E: Unable to locate package libavcodec-unstripped-52. I have multiverse enabled. And I have done sudo apt-get upgrade && sudo apt-get update also. Why am I not able to do it ? Please find attached my copy of /etc/apt/sources.list just to see that my multiverse is enabled.

Please advise,
Thanks.

PS : I tried the extract audio options in youtube-dl, youtube-dl http://www.youtube.com/watch?v=kYfNvmF0Bqw --extract-audio and it works too. But it gives me a file type called m4a that I cannot play in my mp3 player that I find it hardly useful.

[IAMTubby]

Okay, got it working.
I did sudo apt-get install ubuntu-restricted-extras and got it to work.

So , if you are stuck with the same problem some time, steps would be something like :
1. Make sure multiverse is checked from SystemTools -> SystemSettings -> SoftwareSources.
2. sudo apt-get update(make sure that you have updates from main, restricted. universe and multiverse)
3. sudo apt-get install ubuntu-restricted-extras
This is necessary because you actually need to do sudo apt-get install libavcodec-unstripped-52 but I was, and still am unable to install this. It says E: Unable to locate package libavcodec-unstripped-52. So to overcome this, we do sudo apt-get install ubuntu-restricted-extras. This install a whole lot of things, of which one is ffmpeg.
4. Finally, ffmpeg -i videofile.flv filename.mp3

But if someone could tell me why I'm unable to do sudo apt-get install libavcodec-unstripped-52 , it would be great.
Thanks

[FakeOutdoorsman]

For Ubuntu 11.10 you needed libavcodec-extra-53. The package name can vary depending on your Ubuntu version.

[IAMTubby]

For Ubuntu 11.10 you needed libavcodec-extra-53. The package name can vary depending on your Ubuntu version.
Bingo, thanks FakeOutdoorsman.
Would have marked thread as solved but I guess the feature is not active yet on the new site.