Difference between ABR and VBR

ABR and VBR are two of the encoding modes in LAME. They are used to encode audio as well as video files. Many people assume these two are the same or synonyms for each other. However, this is a completely wrong idea. ABR and VBR are two very different aspects although they are both related to encoding. The way they work differs in several manners. In ABR, we decide on a particular target of bitrate. While in the case of VBR, we can set a target for a particular quality.

In this article, we shall aim to learn about ABR and VBR in detail. When we study them individually, it will be easier to chalk out the difference between the two. Also, we will be able to have a clearer idea as well as knowledge.

ABR vs VBR

The main difference between ABR and VBR is that in ABR, the average bitrate is constant. However, when we consider the bitrate in each frame, it is variable. Whereas, in the case of VBR, its bitrate is variable is bitrate throughout. The change takes place concerning the information that needs to be encoded.

ABR vs VBR

ABR stands for Average Bitrate. It is used to tell about the bitrate that we require. Its quality is not as high as VBR. It has different bitrate in different parts which can be higher or lower. Eventually, the average bitrate is obtained for particular audio or video. It is generally measured per second.

On the other hand, VBR stands for Variable Bitrate. It is used to tell about the quality that we want. Its quality is higher than ABR. In this system, it allows the bitrate t vary during parts of particular audio or video. The general advantage of the VBR encoding is an optimum bitrate from one frame to another.

Comparison Table Between

Parameters of comparison.ABRVBR
ConsistencyEach frame has a variable bitrate however the average bitrate is constant. It has a variable bitrate through out.
FocusABR aims in setting the bitrate for the audio or video file.VBR aims in setting the quality of an audio or video file.
QualityThe quality of ABR is not as high as VBR.It provides higher quality than ABR. Also, it has a better quality to size ratio.
SizeIt produces larger files as compared to VBR.It produces smaller files as compared to VBR
Unknown VariantIn ABR, the resulting quality of encoded files is unknown.In VBR, the resulting size of encoded files is unknown.

What is ABR?

Average Bitrate is the average and final value collected from the group of segments. It is measured per second and is obtained by dividing the number of bits. When it comes to quality, ABR is much lower in quality as compared to VBR.

We can also define ABR as the average value or average amount of data that is transferred per unit of time. It is generally used for music files that are referred to as mp3.

It has compromised in its quality due to the usage of lower bitrates. It takes place during the encoding process and is efficient. It is also a quick process which is considered one of the advantages of ABR. It aims in setting the bitrate from audio and video files.

For an accurate encoding, it requires a two-pass encoding. This is because, in the first part, it is quite not possible to know and record the exact bitrate value. Hence, it proceeds in such away. However, the bitrate does not vary a lot.

What is VBR?

VBR is a technology used in telecommunication and computing. It is a form of encoding which is related to the sound or video file recordings. The measurement is generally obtained per second. It provides a great quality which is higher than ABR.

It has a number of segments. Each segment has a variable range of bitrate. This is why it is known as Variable Bitrate. It has a high bitrate and thus needs large storage space. However, the average rate can be calculated to get a fixed value.

The most common use of VBR is to deliver the HTTP of particular video content. The VBR encoding is used to regulate the data rate and the limit set by us. The bitrate of the files keep on increasing or decreasing while proceeding through the segment,

The encoding process is very flexible as well as accurate. It also provides a satisfying quality-to-space ratio. However, the process is time-consuming. The overall procedure is quite complex. Hence the probability of causing errors is high. Also, the compatibility of hardware is a real concern.

Main Differences Between ABR and VBR

  1. The main difference between ABR and VBR is their main target. ABR is used to set the bitrate for the audio or video file. Whereas, VBR is used to set the quality of an audio or video file.
  2. The quality of ABR is not as high as VBR. On the other hand, VBR provides higher quality than ABR. 
  3. ABR stands for Average Bitrate whereas, VBR stands for Variable Bitrate.
  4. Size is quite an important factor in encoding. ABR can produce larger files as compared to VBR.
  5. There is an unknown variable for both. In the case of ABR, it is the quality. However, in the case of VBR, it is the size.

Conclusion

After studying them individually, we can conclude that ABR and VBR are two different types of encoding. The basic difference lies in their file size content. Moreover, ABR is mainly for audio files or mp3. Wherever VBR is mainly for video files. While listening to the respective files, we can draw a distinct difference between their qualities. VBR has a good quality-to-size ratio. Also, its quality is better than ABR.

ABR can provide room for compromise in case there is a shortage of memories. However, when the bitrate is set very low, ABR can eventually result in distorted and poor quality of sound. When the quality is increased, the VBR file remains the same in size. However, the size of it is unknown. It does produce smaller files at a higher setting.

References

  1. https://ieeexplore.ieee.org/abstract/document/658906/
  2. https://ieeexplore.ieee.org/abstract/document/610048/
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