Bit by Bit: When MP3 320 Kbps Isn’t Enough

Posted: May 30, 2010 in Bit by Bit (Digital Audio), music
Tags: , , , , , , , , , ,

For years now, I’ve been happy to rip all my CDs to MP3 at 320 Kbps using the CDex digital audio extractor, which is open source software and does an excellent job. Many people (i.e. not audiophiles) consider MP3 320 Kbps “CD quality”. It isn’t CD quality, but it’s generally good enough. I rip the CDs so I can put them in iTunes and copy them to my iPod, of course, and I use MP3 compression because it allows me to store about four tracks in the space that it would take me to store one WAV (CD) track.

I’ve recently realized that this one-size-fits-all approach isn’t always the best choice.

I purchased Animal Collective’s most recent album, “Merriweather Post Pavilion” through iTunes. I rarely purchase through iTunes because I’d rather buy the CD and rip my own. However, it was late, the shops were closed, I had a craving for some new music, and after a solid recommendation from All Songs Considered I decided I couldn’t wait.

Lossy Compression

iTunes supplies their music in 256 Kbps m4A file, which many say is on a par with a 320 Kbps MP3 file. Lossy compression is used to convert WAV files to each of these file types, which means information is lost during the conversion process, but at these high bit rates the theory is that most people’s ears won’t notice the difference.

The few iTunes albums I purchased previously sound decent enough. On this occasion I wasn’t satisfied. There was a dense, muddy quality to the recording, and I found the album increasingly unpleasant to listen to with each play.

To be fair, when I wrote to iTunes regarding my issues with “Merriweather Post Pavilion”, they replied with a letter saying that they take the quality of their music very seriously. They also gave me a full refund, even though I didn’t ask them to do that.

Wondering what this album really sounded like, I went off to HMV, where I was lucky to find it in the “2 for €12” rack. As usual, I ripped it to the aforementioned MP3 320 Kbps format…and it still sounded like crap! Hmmm, could it be that my ears were waking up from the induced coma caused by years of listening to compressed music, or was there something else going on here?

“Merriweather Post Pavilion” is a great and unusual album pop album. It sounds a bit like what might really have been going on in Brian Wilson’s head the first time he tried to record “Smile” with the Beach Boys – Lush harmonies and clever melodies overlaid with electronic loops, bleeps, synthesized arpegiators, and other subterfuge, This might not sound very appealing on paper, but it all makes sense when you hear the album. Consequently, it is chock full of sound, which means it is loaded with digital information.

Trying to put this simply, this type of compression works by removing information that isn’t being used, and by making compromises with information that is being used. The less information there is, the happier you are going to be with the results. The more information there is, the more compromises there are. Generally speaking, the differences between WAV and MP3 320 Kbps aren’t glaringly obvious. For example, you might notice a little less sizzle in a cymbal, or the guitars might not be as smooth as when they were captured. However, when there is an above average amount of information, as there is with “Merriweather Post Pavilion”, the compromises can be overwhelming, and MP3 simply isn’t good enough.

The obvious alternative might be to copy the Wav files into iTunes. That is, the files as they exist on the CD (which, by the way, was as sonically pleasing as I hoped when I finally listened to it in this format). In such a case there is no conversion, therefore there is no compression. iTunes and iPods play WAV files, although they do require more processing power, so they’ll run down the battery faster. There are also two other issues with WAV files:

  • Storage space overhead (1 WAV album = about 4 MP3 320 KPs albums).
  • Tagging is not supported (i.e.album information and artwork).

Apple Lossless Compression

Up until now I hadn’t tried any of the so called “lossless” compression formats, which provide some compression but render a file that can be converted back to a WAV file without losing any of the information. You can’t do that with an MP3 file. Also, a lossless file should sound more authentic because you’re retaining significantly more of the information.

In this case, I used the Apple lossless encoder, which I had seen referred to in the discussion boards. Even though I’ve used iTunes for years, I wasn’t aware I had this capability, or what it was, or where it was. It’s well hidden in the preferences (at least to me), and the help file is not particularly illuminating. To set iTunes to rip CDs using the lossless encoder:

  1. Select EditPreferences.
  2. On the General tab click the Import Settings button.
  3. Select Apple Lossless Encoder from the Import Using dropdown list.

“Merriweather Post Pavilion” sounded much better in the Apple Lossless format, but it still wasn’t right. There was obvious coloration so that the overall sound was “darker” and still somewhat compressed. In addition, the expected 40%-50% file size reduction from WAV looked to me more like 30% – definitely not worth it for an inferior version. I should point out that this is the only album I have converted to this format. I suspect that the encoder produces better results with most other albums.

AIFF files

At this point I decided to give up on compression for “Merriweather Post Pavilion”, but I wasn’t satisfied with using WAV files without tagging capability. Tagging is what allows you to include information like artist, album, album cover, genre, etc. When you’ve got ten thousand plus tunes on your box, you want to be able to sort them for easy access. However, there is a format that allows you to have the uncompressed music file with tagging – AIFF.

Even though you may never have heard of them, AIFF files have been around long enough to have wide support. In a nutshell, they place the WAV file information in a new container that can be tagged just like compressed audio formats, although placing that information in the file can require more manual labor than when ripping MP3s, depending on how your software is set up.

What did I learn?

Since having this experience I’ve started ripping new CDs to MP3 and AIFF. Most albums, even my Beatle’s remasters, aren’t as dense and complex as “Merriweather Post Pavilion”, so differences between MP3 320 kbps and AIFF files are far less noticeable, although there is no denying they are there.

MP3 320 Kbps is fine for the road 99% of the time. When you have an album like “Merriweather Post Pavilion”, you’re far better off using the extra space to have a version on your iPod you can stand to listen to. That’s easy for me to say, with a 160GB iPod Classic. But it is worth doing this for the few times it will be necessary.

When at home, why wouldn’t you want to hear the best version of the recording? Sure, this requires more storage space, but hard disk costs have been continually dropping for years. For example, I can now buy a 1 TB external hard drive for half of what it cost for a 300GB hard drive four years ago. There is also something to be said for having a back up copy of your CDs in the event they are lost or damaged.

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