Select bitrate for multimedia recording

Bitrate (English) - means the amount (number) of bits that is used to record or transfer multimedia material lasting for one second. When fixing multimedia (audio and video) content in MP3 format, it is block-wise compressed using certain procedures (algorithms). And these algorithms are divided into types depending on the bitrate (its value). On each of these blocks (frames) is allocated from thirty two to three hundred and twenty bits.

Coding

Algorithms VBR, CBR and ABR, used for encoding in MP3 format, do not provide full quality preservation - it is lost. However, this can be felt only when viewing (playing) only on high-quality equipment.

For a non-professional look, the material recorded using the mechanisms of VBR, CBR and ABR, will look quite high quality.

We will analyze the differences in the algorithms VBR, CBR and ABR, in order to know which of them to use correctly for recording and subsequent storage or transfer of files. Which one is better for quality or for other tasks.

Constant bitrate

As the name implies (constant - constant, eng.), In this type of algorithm a constant number of bits is allocated for one second of the material. All blocks are equal to each other.

Through the use of CBR, it is possible to know in advance the size of the source file or the width of the stream. This is important for transmitting information on channels that have a limited width.

Constant bitrate algorithm

The use of such coding is not ideal:

  • when recording empty segments, the flow of the selected bits remains the same;
  • when recording complex fragments for which, in principle, it would be worthwhile to allocate more space, the bitrate also remains set.

Disadvantages of quality when recording “difficult” sections are solved by increasing the bitrate, for example, up to a maximum of 320 kbps, but this increases the width of the transmission stream or the file size.

Variable bitrate

It is easy to guess that this kind of method (VBR) is a variable (variable - variable, eng.).

This encoding is characterized by the fact that the bitrate in this case changes during the encoding process itself by the codec program. And the bit rate in this case depends on the saturation of the sound or video.

That is, when VBR coding is selected by the program for recording empty pictures, a lower bit rate will be selected, and for recording saturated pictures or quickly changing images, a higher one.

Variable bitrate algorithm

The disadvantage of this algorithm is the difficulty of anticipating the upcoming changes. Increasing the bitrate when recording will actually happen late.

In addition, fragments that sound quietly are perceived by VBR coding as fragments that do not carry importance, and under them on this basis is allocated the minimum bitrate.

Therefore, CBR with a maximum value of 320 kbps will provide greater quality.

True, the encoding VBR 2 Pass has now appeared.

Its essence is that the program first analyzes the multimedia stream (for the first time), and then makes a recording, compressing it based on the data obtained during the initial scan. This gives the best result in quality, and in this sense such encoding is better.

Average bitrate

Average is translated from English as averaged. This is a kind of ABR, which is in some way a mixture of VBR and CBR.

Selecting the ABR mode, the user sets its value in kilobits per second. The codec can change it in one direction or another, adhering to the established average value.

Algorithm Average bitrate

The ABR method compares favorably with other assignable bits per second. You can select absolutely any numeric parameter from 8 to 320. While the CBR encoding can use only sixteen times the value.

From the foregoing it follows that if the size of the resulting file is important for the result, then for higher quality it is better to look at the ABR or CBR encoding.

Otherwise, pay attention to the VBR 2 Pass method.

In this article you have read the encodings VBR, CBR and ABR. Now you know what makes each one different, which one is better for your particular task and which one should be chosen.