Q: My iPod has 160GB and should be able to hold around 40,000 tracks however after just over 19,000 being loaded it is now full. Previously I have had over 30,000. So what is wrong this time is there some duplication going on?
A: There are a couple of possible reasons why you may not be able to store as many songs on your iPod as the advertised capacity.
Firstly, it’s important to understand that not all music files are created equally, and can vary in size depending on the format and bit-rate used, and of course the length of the song itself. Apple’s capacity estimates are based on four-minute songs encoded using the AAC encoder at 128 kilobits per second (kbps). A 128kbps AAC or MP3 file takes up approximately 1MB of storage for every minute of audio playback. This means that a 160GB iPod, with 160,000 MB of storage, would be capable of storing approximately 160,000 minutes of music encoded at 128kbps.
With the average song being 4 minutes in length, this translates to approximately 40,000 songs.
However, it’s not uncommon these days for music to be encoded at higher bit-rates, such as 192kbps or 256kbps, and in fact most music purchased from the iTunes Store now comes in a 256kbps AAC format. These bit rates provide higher quality by encoding more audio data for each minute of audio. The result is larger song files to store the additional data required for the higher quality audio: approximately 2MB per minute of audio in the case of a 256kbps file.
Therefore, if your music library is made up mostly of 256kbps AAC or MP3 files, you will only be able to store approximately 20,000 of these on your 160GB iPod.
You can determine the bit-rate and size of your songs simply by choosing View, View Options from your iTunes menu and enabling the Bit-rate and Size columns.
This will display this information in your iTunes library column view beside each of your tracks.
That having been said, another thing to check is to ensure that you don’t have any space on your iPod being taken up by “orphaned” files. iTunes and the iPod use a database to store your track information, and there are some situations in which files can be written to the iPod without being updated into the iPod’s file index. A common cause of orphaned files is unplugging the iPod from your computer without waiting for iTunes to finish syncing with it; since iTunes updates the iPod’s database at the end of the sync operation, this results in a scenario where new content has been copied to the iPod, but the iPod database has not been updated to include this new content.
The result is storage taken up on your iPod that neither iTunes nor the iPod know what to do with. You can easily check if this is the case by selecting your iPod from your iTunes Devices’ list and checking the Capacity bar at the bottom of the screen:
If the orange “Other” bar looks excessively large, this could indicate the presence of orphaned files. Note that it is not abnormal to have some space taken up by “Other” since this represents any data on your iPod that iTunes doesn’t specifically recognize as audio, video or photos. This can include information such as album artwork, iPod Games, or any files you may have stored on your iPod manually as an external hard disk.