Difference between MPEG1, Layer 2 and MPEG1, Layer 3

Question

Difference between MPEG1, Layer 2 and MPEG1, Layer 3

I noticed I have 20 songs in my Library that won't copy to my ipod. Upon inspecction I found that these songs, even though their extension is .mp3 are MPEG 1 Layer 2 instead of Layer 3, which seems to be the codec the ipod can play (correct me if I am wrong please).

What are the differences between these two codecs? More importantly, how can I convert the files to the correct codec so I can put them in my ipod?

Finally, out of the 20 songs I have identified 11, my Library is 3000+ songs, is there an easy way to search for the other 9 without going through all the Library?

Thanks in advance.

Running iTunes 6.0.1, ipod software updated to 3.1 (up to date)

Ibook G4, 768mb RAM Mac OS X (10.3.9)

Posted on Dec 21, 2005 3:06 PM

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Answer 1

cabin

Level 1

0 points

Jan 26, 2006 8:43 AM in response to Fernando Cuenca

Did you ever get an answer to this? I have the same problem. I've downloaded from the internet some Spanish lessons that are MP3 files, but when they are imported into iTunes they are MPeg-1, Layer 3. I can't move them to my iPod.
Nancy

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Answer 2

Jan 28, 2006 4:57 AM in response to Fernando Cuenca

Hi Fernando,

Welcome to Apple Discussions

What are the different layers in MPEG-1?
The different layers have been defined because they all have their merits. Basically, the complexity of the encoder and decoder, the encoder/decoder delay, and the coding efficiency increase when going from Layer I via Layer II to Layer III.
Layer I has the lowest complexity and is specifically suitable for applications where also the encoder complexity plays an important role.
Layer II requires a more complex encoder and a slightly more complex decoder, and is directed towards 'one to many' applications, i.e. one encoder serves many decoders. Compared to Layer I, Layer II is able to remove more of the signal redundancy and to apply the psychoacoustic threshold more efficiently.
Layer III is again more complex and is directed towards lower bit rate applications due to the additional redundancy and irrelevancy extraction from enhanced frequency resolution and Huffman coding.

Found this with Google on http://www.tnt.uni-hannover.de/project/mpeg/audio/faq/mpeg1.html#1A

Regards,
Colin R.

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