Help – My MP3 Won’t Play! CBR vs VBR Files

A reader contacted me recently about a problem he was having with his car’s audio player. It refused to read some of the MP3s on his USB stick. This a common problem with older media players, and this week we will dip our toes into the consumer electronics world and see why an MP3 won’t play on your system.

The Problem: Some of My MP3s Will Not Play on My System

At thirty years old, MP3 is a dinosaur in the rapidly evolving tech world. Over the years, the format has been tweaked in order to increase compression and mitigate loss of quality.

Those of us in the pro audio world may already know this, but it may be news to the average Joe just looking throw some tunes on a thumb stick and play them in the car. This could be a problem for DJs as well, as some DJ media players – particularly older models – may not play nice with certain types of MP3 files.

The reason for this incompatibility is the emergence of another type of MP3. The variable bit rate (VBR) MP3 became a way to further reduce file size without further sacrificing quality. (For a thorough explanation of bit rates, read this article) Your standard MP3 file is encoded using a fixed, or constant bit rate (CBR).

Constant vs. Variable Bit Rate – CBR vs. VBR

Bit rate is the resolution of your media – the higher the resolution, the better quality of your audio. But what if you’re listening to a song with a few beats of complete silence before the band goes off again? Do you need the highest possible resolution to play back silence?

Of course not! And that’s precisely what the software engineers who developed VBR figured as well. Their codec will vary the bit rate depending on the complexity of a media segment. Silence will have a low bit rate because there is no information to relay. A loud passage with a blistering guitar solo will have a much higher bit rate because there is a wealth of information to convey. The codec will analyze segments of music and continuously adjust the bit rate according to complexity.

And therein lies the problem: the variable nature of VBR MP3s causes older media players to reject them as unsupported formats. Fortunately the solution is simple, and you can solve it in a minute or two.

The Solution: Identify and Re-Encode Your VBR MP3s

Identifying the VBR MP3 files can be a challenge because most software won’t differentiate the two types of MP3 file. Without getting too technical, there is a simple way to differentiate the two in iTunes.

1. Open iTunes
2. If you haven’t already, display a “bit rate” column in song view
3. Look for “odd numbered” bit rates. Constant bit rates will be one of the following values: 96, 128, 192, 256, and 320. Anything outside this set of values is an average bit rate – a common indicator of VBR MP3 files.

Fortunately, re-encoding your VBR files is a simple process. All you need is a converter. There is a wealth of encoders out there, but the best is LAME – a reliable, open-source codec that has been around for a quite long time. But for the purposes of this example, we will be using Audacity (which incidentally also uses LAME to encode MP3).

1. Open Audiacity (available for free here)
2. Ensure LAME for Audacity is installed, available here.*
3. Open the VBR MP3 file giving you problems
4. Go to File > Export Audio
5. Ensure you select Constant as the Bit Rate Mode and select the quality you wish to use. (Again, for more information on bit rates, read here)
6. Complete the export

The exported file will be a fully compatible CBR file encoded to the bit rate of your choosing. This file will work on any media player that reads MP3.

*Due to patents, LAME used to be separate from Audacity, but it is now built in. Linux users still need to install it. If you don’t have it, MP3 will not be an export option.

Conclusion

So why use VBR at all? Disk space has become so vast and affordable that there is no real reason to further compress an audio file. Additionally, the size difference between a CBR and VBR file is often negligible. You won’t be reducing your file size by half. You won’t even get to 75% in most situations. Truth be told, if you are looking for smaller files of comparable quality, you would be better off using Apple’s AAC format – it’s much newer compressed audio format delivering equivalent quality at a fraction of the size. And AAC is supported by most media players.

Until next week,

Chris Lazaga
AudioMunk