what does bit rate vbr mean Archives

Audio Coding Part5

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Audio Coding Part5

VBR

About VBR

VBR Encoding

VBR: An interesting feature of MP3 files is that they can be read and played, which is also in line with the most basic features of streaming media. That is, the player can play without first reading the entire content of the file and play where it reads, even if the file is partially damaged. Although mp3 can have a file header, it is not very important for mp3 format files. Because of this feature, each frame of an MP3 file can have a separate average data rate without a special decoding scheme. That is why there is a technology called VBR (Variable bitrate, dynamic data rate), which allows each segment or even each frame of an MP3 file to have a separate bitrate, the advantage of this is that the sound quality is guaranteed to the maximum. . File size is limited. The advantages of this technology are obvious, but it is really difficult to use, because it requires the encoder to know how to assign the bitrate to each segment, which is like a dummy for encoders without waveform analysis. As such, VBR technology didn’t seem glamorous as soon as it appeared.
Experts have found that the human ear has a protective effect through long-term acoustic research. The sound signal is actually a type of energy wave, which propagates in air or other media. The most direct response of the human ear to the amount of sound energy, that is, the volume or pressure of the sound, is to hear the size of the sound. We call it the volume, which means the volume. The unit of energy is the decibel (dB). Even sounds of the same volume can be perceived by people as different in size due to their different frequencies. The 500 Hz frequency is most easily heard by the human ear. No matter whether the frequency is increased or decreased, even if the volume is the same, everyone will feel the sound become smaller. But when the volume drops to a certain level, the human ear cannot hear it, and each frequency has a different value.
You can see that this curve basically forms a V. When the frequency exceeds 15000 Hz, the human ear will feel that the sound is very small. Many people who are not very good at hearing cannot hear the frequency of 20000 Hz at all, no matter how loud it is… When the human ear hears two sounds with different frequencies and different volume at the same time, the one with the lower volume will also be ignored. For example, it is hard to hear the sound of the computer cooling fan during the day, but it becomes a noise source at night. According to this principle, the encoder can filter out many inaudible sounds to simplify information complexity and increase the compression ratio without significantly reducing sound quality. This shading is called the simultaneous shading effect. However, sound A is protected by sound B. If A is within the protection range centered on B, the protection will be more obvious. This range is called the critical bandwidth. The critical bandwidth of each frequency is different and the higher the frequency, the larger the critical bandwidth.
Frequency (Hz) Critical Bandwidth (Hz) Frequency (Hz) Critical Bandwidth (Hz)
Based on this effect, the experts designed a mental model of human hearing. After this model was imported into mp3 encoding, it led to a momentous revolution in sound quality. gradually eluted. At this point, the VBR technology, which has been buried for a long time, shines brightly, and with the use of the psychological model, it can perform powerful temptation and lethality.
For a long time, many people have a bad impression of MP3. More and more people think that the best sound quality of WMA is better than MP3. This statement is not correct. At medium and high bit rates, properly encoded MP3 is much better than WMA. It’s close to CD quality, with not-so-great hardware support, not many people can tell the difference between the two, it’s not a fairy tale, though you used to be able to easily tell the difference between MP3 and CD blindly. listening, but now cannot guarantee that it can distinguish correctly. Because MP3 is an excellent codec that was buried before.

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What is bit rate and what is it for?

What is bit rate and what is it for?

bitrate

If you become familiar with the term, you can understand that there is nothing supernatural about it.

Bit-Rate

This value can be found in multi-server settings when people are streaming video and audio.

For example, when making desktop and online converters. To understand how to change the video and audio bitrate, you need to go to a specialized site, where, in principle, more information on how to do it.

Also, it should be borne in mind that you can not do without a special program. It should be used 100 percent and only after that will it be possible to see the result on whether the bit rate has been changed in the video or audio file.

There really is a lot that you can achieve with modern software. What features of the term should I pay attention to? It should be noted that the bit rate is translated exactly as the width of the stream. Basically, it is the amount of information that is transmitted or processed per second of time.

This concept is more related to the multimedia sphere, for example, the video information that can be seen on the screen in one second – this is the bit rate. Among the characteristics are the following: To measure bit rate, one must understand what a kilobit per second is. This is the transmitted information that can be viewed. Thanks to the VideoMaster program, the kilobit can be tracked visually.

A video clip where the low bit rate is one that is low quality in digital format. Also, you can see how the video looks blurry, dull, and pixelated during streaming. At a high quality bit rate, you can see a wide color gamut, as well as hear a high enough quality sound, because the music gamut will be really distinguishable and clear. Varieties include: a constant type of bitrate, variable, averaged.

All of them can be viewed using the VideoMaster program, which directly adjusts the video to every second. Bitrate can be used in the program in any specific situation to remove one second or another from the video, or leave it.

What is the bit rate?

What is the bit rate?

What is bit rate

What is the bit rate? It is difficult to do without this term when we talk about audio and video files. It is not difficult to understand what you need to see behind this term. Even someone who is far from any modern technology.

What is bit rate

First, you need to understand that there is a general principle for compressing and encoding files. For example, MP3 encoding assumes that the original audio file must be cut into chunks, the length of which will be 50 milliseconds. Each of these fragments is analyzed separately to break down into harmonics.

A person perceives the sound with the ear so that it throws out those harmonics that it perceives worse. That is, quieter sounds, when the loudest are heard, you do not perceive them. Therefore, due to the inertia of hearing, a person makes masked sounds. This means that you will not be able to hear any short-term signals that will pass in a fraction of a second, for example for a clap.

Information about the harmonics remaining after filtering is recorded in an MP3 file. It is significantly smaller than the original WAV. A WAV file is a complete repository of information about the original sound, which is digitized and quantized at 44 kHz. The resulting information is stored on normal audio CDs.

When playback is in progress, reverse conversion is performed. That is, the remaining harmonics are transformed back into a sound wave. Some of the information about the original signal is lost because the sound does not match the original. Since insignificant sounds were removed, the human ear does not distinguish the signal from the original. The same as it was before packing in MP3.

This means that the bit rate should be called the amount of information per unit of time. The essence of the bit rate is how much information we can spend on each second of recording. The smaller it is, the smaller the size of the files of the same length in time. This means that it will be necessary to eliminate a greater number of “extra” harmonics.

The higher the bit rate, the larger the file size and the higher its quality. For bit rates, units of measure are provided: kilobits per second (Kbps) and megabits per second (Mbps). The MP3 audio compression algorithm is mainly used with 128 kbps compression.

There are also two types: constants and variables. For example, in video compression, when using a constant bit rate, a fixed amount of data is used to encode one second of a movie. With a variable bit rate, depending on the scene in the movie, the codec sets its own bit rate value.