Converting Youtube videos to MP3!

Yesterday I have downloaded two fantastic songs from Youtube. Later, I wanted to move them to my mobile as MP3. As the downloaded vidoes are in FLV format, I would need to convert them to MP3. I thought, no problem, I have ffmpeg install in my LinuxMint :).

I hit the following command:

ffmpeg -i videofile.flv -f mp3 musicfile.mp3

Grrrrrrrr! I got an error something like unsupported codec.

Later, I found a solution here. It is quite simple. He said, the audio format in the FLV is already in MP3. So a stream copy will be enough. Here is the command I ran:

ffmpeg -i videofile.flv -acodec copy musicfile.mp3

Great! It is converted without any issue and the file properties also says it is MP3. However, to be sure whether by default Youtube video’s audio is mp3 or not, I read the wiki page.

Here it is mentioned that Youtube now uses AAC format (most probably from February, 2009). My question is how then a simply stream copy worked earlier? Is it due to for AAC being the successor of MP3?