Difference Between ABR and VBR

ABR vs VBR

Initially, MP3 presented a huge reduction in file size without too much loss of quality. Compared to a standard CD, the file size of an MP3 may be around one tenth. The introduction of VBR (Variable Bitrate) encoding introduced even more improvement by varying the number of bits used per section of the sound file to reach the desired quality level. ABR (Average Bitrate) is one way of encoding a VBR file. In ABR, the user sets a certain bitrate. Certain parts of the song may have lower or higher bitrates but the overall bitrate of the sound file would stick to the value that has been set.

The most significant difference between the two is which aspect of the sound file it holds constant. A VBR encoded file would always strive to keep the quality constant while ABR strives to keep the file size constant. You can therefore deduct that the final file size of VBR file would not be known until the encoding has finished. And in similar fashion, you would not know the quality of the file until you listen to it. For this reason, it is better to encode your music files into VBR as quality is often the desired quality of a sound file. But for those who have limited memory, ABR may provide a compromise.

Generally, VBR encoding creates a file that has a better quality to size ration than ABR encoding. It may not be smaller for some files, but it would have better sound quality. Setting the bitrate very low for ABR may result in a very distorted sound quality.

Although the quality of the file may greatly vary at the lower bitrate levels, the differences start to disappear once you increase the bitrate significantly. At some point, the qualities of the files become identical, though it would be much bigger than what you’d expect. As you increase the quality or the bitrate even further, a VBR file would remain the same in size while an ABR file would continually increase. This is because VBR would not use more space than it really needs to while ABR needs to fulfill the bitrate setting.

Summary:

1. ABR is one way of encoding VBR audio files

2. ABR sets the bitrate for the entire audio file while VBR sets the quality level of the file

3. The resulting quality of ABR encoded files are unknown while the resulting file size of VBR encoded files are unknown

4. VBR generally produces better quality to size ratio compared to ABR

5. VBR would produce smaller files at very high settings compared to ABR

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