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CBR and VBR Encoding FAQ: What is The Difference?

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Question: CBR and VBR Encoding FAQ: What is The Difference?

If you want to rip your music CDs to an audio format such as MP3, WMA, AAC, etc., or need to convert between formats then it's a good idea to know what CBR and VBR mean before you start. This FAQ aims to give you a primer on what these two abbreviations mean, how they work, and the difference between the two encoding methods.

Answer:

CBR Encoding

CBR stands for Constant Bit Rate and is an encoding method that keeps the bitrate the same. When audio data is encoded (by a codec), a fixed value is used such as: 128, 256, 320 kbps. The advantage of using the CBR method is that audio data is typically processes faster (compared to VBR). However, the files that are created aren't as well optimized for quality versus storage as VBR.

For more information, read our CBR definition article.

VBR Encoding

VBR is short for Variable Bit Rate and is an encoding method that enables the bitrate of an audio file to dynamically increase or decrease -- a target range is used for VBR; the LAME encoder for example can be between 65 - 320 Kbps. Audio formats such as MP3, WMA, AAC, and Vorbis support VBR as well as the standard CBR as an encoding method. The biggest advantage of VBR (compared to CBR) is sound quality to file size ratio. You can usually achieve a smaller file size by encoding audio with VBR than CBR because of the way bitrate is altered depending on the nature of the sound. For instance, the bitrate will be significantly reduced for silence or quieter parts of a song. For more complex areas of a song that contain a mix of frequencies, the bitrate will be increased (up to 320 Kbps) to ensure sound quality is maintained. This variation in bitrate will therefore help to reduce the storage space needed compared to CBR.

However, the disadvantage of VBR encoded files is that they may not be compatible with older electronic devices as CBR is. It also takes longer to encode audio using VBR because the process is more complex.

Which One Should I Choose?

Unless you are restricted by old hardware that only supports audio formats encoded using CBR, then VBR is usually the recommended method. Support for VBR in hardware devices like MP3 players, PMPs, etc., used to be hit and miss, but these days it's usually a standard feature. As mentioned earlier, VBR gives you the best balance between quality and file size. This is therefore ideal for portables that have limited storage or where you want to make efficient use of other storage solutions like USB flash drives, flash cards, etc.
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