When compressing audio and video files, the MP3 bit rate indicates how many bits are available to the decoder to encode exactly one second of a track. The higher the bit rate of the MP3 file, the better the quality achieved. The bit rate can be constant (constant bit rate, CBR) or variable (variable bit rate, VBR). Our guide explains the differences.

MP3 has established itself as a leading music format on the Internet in recent years and all popular MP3 players support this format. It was developed by the Fraunhofer Institute and is now considered the best known standard for Audiocodierun g. But where are the differences in the jungle of MP3 bit rates?

What MP3 bitrates are there anyway?

A distinction is made between the following common bit rates for MP3 files:

32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 and 320 kBit / s.

This increases the quality of MP3s, but also the size of the files created. Compared to the original, an MP3 file only requires about 10 percent of the original storage space.

Starting at a bit rate of 192 kbit / s, you can hardly hear any difference from the quality of the original CD in many pieces of music.

Low bit rates: 32 to 128 kBit / s
Average bit rates: between 128 and 192 kBit / s
High bit rates: more than 192 kBit / s

What is the best bit rate for MP3 compression?

Again and again the question arises of what bit rate to select when converting songs to MP3 to achieve roughly CD quality. An MP3 compression with 192 kbit / s variable bit rate here is an ideal compromise between size and quality.

At just 128 kb / s, you can often hear a distinct difference from the original songs on CD. Music pieces with a lot of dynamics suffer more if the compression is too high (weak bass, lack of treble). So here it is better to use a higher bit rate.

How does the quality of bit rates differ depending on the compression method?

Constant Bit Rate (CBR)

With constant bit rate, each unit of time (for example, one second) is always allocated the same amount of storage space in the entire MP3 file. Therefore, the quality may vary depending on the piece of music. For this, the size of the resulting file can be calculated more precisely.

Variable Bit Rate (VBR)

Variable bit rate is usually the best compression method for normal use, as it can be used to produce consistent high quality. With Acapella parts, 320 kBit / s are not required, as only a few complex frequencies need to be encoded here. However, if you are playing a full orchestra, 128 kBit / s is usually not enough to cover the entire frequency spectrum of the various instruments. Depending on the piece of music, more bits are used when they are important, or those that are not can be omitted. In return, the file size varies more.

Average Bit Rate (ABR)

Some MP3 encoders also support average data rates. Technically, this variant is almost identical to Variable Bit Rate (VBR). Here, too, the encoder software always tries to achieve a uniform quality of the musical piece. However, the bit rate achieved often deviates slightly.

As an example: if you want a target bit rate of 128 kBit / s, then the bandwidth of the achieved bit rate is between 120 and 140 kBit / s. To achieve the desired average bit rate as accurately as possible, some codecs offer a two-pass compression process. The material is analyzed first and is only encoded in the second run. The ABR mode corresponds to a mix of CBR and VBR and is therefore qualitatively more in the middle.