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Talking about some basic differences between VBR and CBR in mp3 files Part 3

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Talking about some basic differences between VBR and CBR in mp3 files Part 3

CBR vs VBR

For VBR encoded mp3 files, since the bit rate of each frame is not fixed, the data size of each frame is arbitrary.

CBR vs VBR

Obviously, the size of the data reproduced per second is different. In this way, the duration of all the audio cannot be calculated with the above formula and other data fields are needed, which is one of the shortcomings of VBR technology: it is relatively difficult and complicated to calculate the duration of the audio.

There is another disadvantage of VBR technology. When playing an audio file, there will inevitably be an operation to jump to the position of the specified time to play (ie, the so-called seek operation). At this time, it is necessary to convert the time position of the target to the position of the file. Then jump to this file position offset to read and decode. If it is a download and play network playback mode, you must first calculate the position of the file during the search operation. Jump to this position and download a paragraph before continuing to play. . For CBR encoding, the conversion to file position offset is also very simple, using the following formula:

file position (byte) = target time position ( s ) * bitrate (kbps) * 1000/8 + id3v2 field size (if any)
But for VBR encoding, it is obviously impossible to use this formula to convert file position. The reason is also very simple: the bit rate of each frame is not fixed and the length of data per second is not average. Therefore, just like calculating duration, other data fields are needed.

The method to calculate the duration of the audio and implement the seek operation using VBR encoding
To solve the above two problems, VBR encoding adds some data fields. At present, there are mainly two types of VBR encoding technologies, one is the Xing specification proposed by the Xing Company, and the other is the VBRI specification of the Fraunhofer encoder. This article only presents how the Xing specification solves the audio duration computation and the implementation of the seek operation.

The main content of the Xing specification is the Xing header, which means that the first audio frame at the beginning of the VBR-encoded mp3 is not used to store specific audio data, but to store additional audio information. This information is marked with the four characters of “Xing” as the beginning of the field (some files also use the four characters of “Info” as the beginning of the Xing header).

The position of the Xing header in the first audio frame is after the standard 4-byte mp3 audio frame header. Between the table header and the Xing header, there will be a blank part with all 0 data content. This blank The length of the section is specified. After the decoder parses the frame header of the first audio frame, it skips the blank part of the specified length, and then judges whether the next content is the four characters of ‘Xing’ or ‘Info’ to judge the audio If the VBR encoding.

The length of the blank part is determined by the mpeg version and the number of channels, as shown in the following table (unit is byte):

non-mono infectious mononucleosis MPEG version
MPEG 1 18 32 (most common)
MPEG2 9 18
The following figure is an example of the field structure of the first VBR-encoded mp3 data frame:

The field structure and the content of the information stored in the Xing header are as follows:

Location (from marker ‘Xing’) longitude direction Example
0 4 VBR header tag, 4-byte ASCII characters, content is ‘Xing’ or ‘Info’ ‘Xing’
0 4 A flag indicating the specific content of the VBR header, the combination is logical OR. The area is
mandatory
. exists, excluding tags;
0x0004 – TOC index storage area set to exist;
0x0008 – Quality Indication Storage Area set to exist 0x0007 (meaning total number of frames, file length and TOC storage area are valid)
8 4 Stores the Big-Endian value of the total number of frames 7344
8 or 12 4 Stores the Big-Endian value of the file length, in Bytes 45000
8, 12, or 16 100 The TOC table, which is a byte array with a length of 100, is a positional index used for fast addressing in the file and is primarily used to resolve the implementation of the seek operation.

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Talking about some basic differences between VBR and CBR in mp3 files Part 2

CBR vs VBR

The appearance of VBR encoding technology is to solve the problem of this waste of space.

CBR vs VBR

VBR technology selects the most suitable bit rate for each audio frame. For audio frames with a lower pitch, the bit rate will be lower and the data size will be smaller. If the pitch is higher, the bit rate will be higher. The size is larger. In this way, the storage space of the audio data can be saved and the size of the mp3 file can be further compressed without losing the audio quality.

The figure above briefly compares the differences in data content between CBR and VBR mp3 files. It can be seen that the bit rate of the VBR encoded mp3 is not necessarily the same due to the difference in data content between frames. Generally, VBR technology will compress and encode in the range of 8~320kbps, so the bit rate of the whole file is higher than that of the whole file. Constant CBR encoding, VBR encoding has a bit rate variable bit rate throughout the file, hence the name VBR (variable bit rate).

In addition to the two encodings CBR and VBR, there is also an ABR (Average Bit Rate, Average Bit Rate) type encoding, which is basically the same as CBR, most audio frames are encoded at the bit rate specified, but they will be The content is encoded with a higher bitrate than specified, but usually this content is short, so there is not much difference in file size compared to CBR, so this type is not common.

Disadvantages of VBR technology compared to CBR technology
Using VBR technology to encode and compress mp3 files can certainly optimize file size, but at the same time, it also brings some new problems in acquiring audio information and monitoring playback progress.

The first is the calculation of the duration of the audio. If it is CBR encoding, since the bit rate is constant, the data size of all audio frames is fixed, so the data size needed to decode for each second of playback is the same, so it is very simple to calculate the audio time length. Just use the following formula:

timelength ( s ) = (total file length (Byte) – total id3 field size (if present)) * 8 / (bitrate (kbps) * 1000 )
In the formula, the id3 field refers to the basic information field that is placed at the beginning or end of the mp3 file, and is generally used to record the audio file name, singer name, and album name. The id3 is divided into two versions, v1 and v2, and v1 only registers. The above three types of information, and the size is fixed, are usually placed at the end of the file; v2 is more flexible than v1, the type of the recorded information is not limited to the above three, and the size is not fixed, it is usually placed at the beginning of the file. The id3 field is an optional field, and the mp3 file doesn’t necessarily have it, so to calculate the audio time of the mp3, you must first read it to see if the id3 exists.

Talking about some basic differences between VBR and CBR in mp3 files

CBR vs VBR

From the perspective of bitrate encoding, one of the most common audio file formats, MP3, can be divided into two types: one is constant bitrate CBR (constant bitrate).

CBR vs VBR

The bit rate of a frame is constant and unique. ; the other is Variable Bit-Rate VBR, which is the opposite of CBR. The bit rate of each frame is not fixed. The bitrate may or may not be the same. Due to the existence of these two types, some jobs that need to be done when playing mp3 files, such as getting audio information and controlling playback progress, need to be handled separately.

Introduction to some basic concepts.
To clearly understand the specific differences between CBR and VBR, you need to understand an important attribute of audio files: bit rate, also known as bitrate or bit rate, refers to the number of bits transmitted per second. The unit is bps (bits per second). The higher the bit rate, the higher the data transmission speed. Bitrate in audio refers to the amount of binary data per unit of time after converting an analog sound signal to a digital sound signal, which is an indirect measure of audio quality.

The bitrate unit of audio files is generally kbps, 1 kbps = 1000 bps. The default bitrate of mp3 is 128kbps, but the mp3 downloaded from the net is more common at 192kbps, and if you want to get high definition mp3 with better sound quality, the bitrate usually reaches 320kbps. The higher the bitrate, the better the sound quality, but the more disk space it will take up.

In general, the higher the pitch of the sound clip, the more space it needs to store and the higher the bitrate. The traditional mp3 file is encoded with CBR, that is, the bit rate of each frame is the same, which brings a problem: if the bit rate of each frame is the same, then the data size of each frame it’s the same way, no matter the pitch of this frame is high or low, the storage space of the audio frame with the highest pitch in all audio is used to store this frame, but for the audio frame with low pitch, not much storage space is needed. This will result in a loss of storage space and will virtually increase the size of the mp3 file.

MP3 bitrate encoding mode

VBR, ABR and CBR.

Generally, there are three mp3 bitrates namely VBR, ABR and CBR.

VBR, ABR and CBR.

1.1 RBC
CBR is short for Constant Bit Rate, which means Fixed Bit Rate in Chinese.

For a CBR MP3 song with a bitrate of 128kbps, the first 128kb of the song describes the sound of the first second, and the second 128kb describes the sound of the second second…if the song is finished, it will take 640 seconds , then the size of the song is 128kb × 640 = 80Mb = 10MB. The so-called 128kbps means 128kb per second.

If you are careful, you will find that the volume compressed by this encoding method will be very large, because the bit rate is fixed. Of course, the sound quality has some advantages over the other two, although this advantage may be minimal.

1.2VBR
Dynamic bit rate VBR (Variable Bitrate). That is, there is no fixed bitrate and the compression software determines on the fly which bitrate to use based on the audio data being compressed.

A simple understanding is that the bitrate will be relatively high at the time the song is rich in detail, and relatively low at other times, so sound quality and size are taken into account. For example: at the beginning of the song, a person sings alone, the sound is relatively simple, we use 64kb to describe the sound within one second; at the climax of the song, everyone sings, the sound is more complicated, we use 256kb to describe a second voice within the species.

1.3 APR
ABR (Average Bit Rate) Average Bit Rate is an interpolation parameter of VBR.

For example, when you specify 192kbps ABR to encode a wav file, Lame will use a fixed 192kbps encoding for 85% of the file, then dynamically optimize the remaining 15%: complex parts are encoded with more than 192kbps, simple parts are encoded with less than 192 kbps. Compared to CBR 192kbps, ABR 192kbps has a similar file size, but the sound quality is much better. ABR encoding is 2 to 3 times faster than VBR encoding and has better quality than CBR in the range of 128 to 256 kbps.

It can be used as a compromise between VBR and CBR. Under normal circumstances, files with this encoding method are rarely found.

VBR Part 2

vbr

For audio compression, such as MP3, the traditional CBR (Constant Bit Rate) is a static bit rate.

vbr

CBR accepts that the MP3 sampling rate is a fixed value. An MP3 is compressed with a fixed value like 128 KBit/s from start to finish. VBR adopts a new compression method with full dynamic adjustment technology to strike a balance between sound quality and file size. When VBR encodes an audio file, the program will try to maintain the selected quality of the entire file and will select different bit rates to encode different parts of the music file. When in the low range (simple part), VBR will automatically use a lower bit rate, such as 32 KBit/s, to compress the sound quality; when in the high range (complex part), it will use a higher bit rate, such as 224 KBit/s. s to compress sound quality Compression is performed; at the high end, use up to 320 KBit/s for compression. VBR MP3 maximizes MP3 sound quality while controlling file size. VBR automatically allocates fewer bits to the simple part of the content during encoding, leaving enough bits to generate high-quality complex parts. The output result of VBR encoding is of better quality than that of CBR encoding, and the encoded file is relatively small and suitable for storage. However, the disadvantage of VBR is that the amount of computation is large, the compression time is long, the size of the compressed file cannot be estimated during encoding, the requirements for the decoding algorithm are also much more complicated, and the Requirements for the hardware (such as the CPU) of the decoder are also high.
Differences between CBR and VBR:
(1) CBR: The size of the FRAME with a fixed bit rate is also fixed. As long as the total file length and frame length are known, the total mp3 playback time can be calculated from the 26 ms required to play each. frame, and can also be controlled by counting the number of frames. Fast forward, fast rewind, slow playback, etc.
(2) VBR: VBR is an algorithm released by XING company, so there will be the keyword “XING” in the FRAME of MP3 (many popular small software can also do VBR compression, whether they abide by this agreement, then it is impossible to Got it), it is stored in the first valid FRAME in the MP3 file, and identifies that the MP3 file is VBR. At the same time, the first FRAME stores the total number of FRAMEs in the MP3 file, making it easy to get the total playing time. At the same time, there are 100 bytes that store the INDEX of the 100 time-sliced FRAMEs. of the total playing time.
beginning
Edit
VBR is a variable encoding rate MP3 compression method. Its principle is to encode the complex part of a song with a high bit rate and the simple part with a low bit rate. Through this dynamic adjustment of the encoding rate, the sound quality can be improved. additionally obtained and the size of the file. Its main advantage is that the entire song can approximately meet our sound quality requirements, but the disadvantage is that the size of the compressed file cannot be estimated during encoding.
Most MP3 players released now support VBR, but although some machines can play songs in VBR format, they cannot display the playing time correctly (especially in car stereos). Many high-quality MP3s today are encoded with VBR. when purchasing, please pay attention to whether MP3 Walkman supports VBR effectively.
other acronyms
Edit
VBR: Valid Business Reason
VBR: Vector Base Register
VBR: Vertebral Body Replacement
VBR: Virginia Blue Ridge Railroad
VBR – Variable Diameter Ram (Oil Drilling)
VBR: Basic Rule Violation (Oregon Traffic Division)
VBR: Kind regards
VBR: ventricle-brain ratio
VBR: Virgin Branson Richard
VBR: Visual Basic custom control file control file,
Visual Basic customization
VBR: VärnamoBygdens Ryttarförening VärnamoBygdens Ryttarförening
VBR: Visions come true
VBR: Vinnell, Brown and Root Vinnell, Brown, Root
VBR: Varsity Brands, Inc. Some brand companies

VBR

VBR (variable bit rate) dynamic bit rate. That is, a bit rate is not fixed.

VBR

The audio encoding software immediately determines which bitrate to use based on the complexity of the audio data during encoding. This is an encoding method that is premised on quality and takes file size into account.
Table of Contents
1 Definition
dynamic bit rate
other meanings
2 differences
3 principles
4 Other acronyms
definition
Edit
dynamic bit rate
VBR is also called dynamic bit rate encoding. Using this method, you can choose various transition levels from worst sound quality/maximum compression ratio to best sound quality/minimum compression ratio. When encoding the MP3 file, the program will try to preserve the quality of the entire selected file, the encoding will choose different bit rates suitable for different parts of the music file. The main advantage is that the sound quality of the entire song can approximately meet our quality requirements, but the disadvantage is that the compressed file size cannot be estimated during encoding.
Bitrate is the bitrate (speed) of the waveform [be careful not to confuse with sample rate, MP3 sample rate is generally 44.1 KHz and some higher ones are 48.0 KHz ], sound is naturally a waveform, that is, vibration. The vibration is drawn as an oscillating curve and the computer is on this curve when saved.
The best (highest) mp3 bitrate is 320 kbps (i.e. 320 kilobits per second), the waveform below 320 kbps will be corrupted and a lot of non-sharp detail will be lost (wave clipping) , while 320 kbps MP3 encoding mainly compresses treble details. Above 320 kbps, only a few programs support encoding, and the sound quality improvement is not obvious, so it is better to use lossless compression.
The higher the bitrate, the more accurate the waveform reproduction and the less distorted the sound. VBR is a technology that does not allow all music to take the same bit rate. The encoder determines the bit rate according to the complexity of the audio. Through dynamic adjustment, the music bitrate is high at complex places and the bitrate at simple places is low, so files of the same size will sound higher quality.
other meanings
VBR variable diameter gate (variable bore ram). Oil vocabulary in English (V1)
the difference
Edit
For video, VBR is different from fixed bitrate mode, and its bitrate can vary with image complexity, so its encoding efficiency is relatively high, and there are few mosaics of fast-moving images. When compressing, the encoding software immediately determines which bitrate to use based on the video data, not only ensuring quality but also taking file size into account. In this way, the encoding program can choose from the worst video and audio quality (usually the highest compression ratio) to the best video and audio quality (usually the lowest compression ratio) among various video qualities. When encoding a video file, the encoding program tries to maintain the selected quality of the entire file by choosing different bit rates to encode different parts of the video file.

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.

CBR VS VBR | What is the difference?

CBR vs VBR: A Detailed Comparison of Video Encoding

CBR (Constant Bit Rate) and VBR (Variable Bit Rate) are two popular video encoding methods used in digital multimedia applications. CBR, as the name suggests, maintains a consistent bit rate throughout the entire video, ensuring predictable file sizes but potentially sacrificing video quality in complex scenes. On the other hand, VBR adjusts the bit rate dynamically based on the complexity of each frame, resulting in higher quality in visually demanding scenes while optimizing file size during less complex parts. When deciding between CBR and VBR, content creators need to consider their specific needs and the trade-offs between consistent file sizes and varying video quality.

CBR vs VBR: The Impact on Video Quality and File Size

The CBR vs VBR debate often centers around video quality and file sizes. CBR ensures a stable bit rate, which can be beneficial for streaming applications where a consistent connection speed is required. However, this uniform bit rate might lead to over-allocating bits for simple frames, resulting in a lack of efficiency. On the other hand, VBR allocates more bits to visually complex scenes, leading to improved video quality and reduced file sizes in comparison to CBR. For applications where storage or bandwidth is a concern, VBR offers a compelling advantage, as it maximizes video quality while minimizing the overall file size. However, VBR’s dynamic nature can lead to challenges for real-time streaming or constrained network conditions, where a constant bit rate might be preferred for smoother playback.

CBR vs VBR: Choosing the Right Encoding Method for Your Video Content

When selecting between CBR and VBR, content creators must carefully assess their specific video content and its intended use. CBR is well-suited for scenarios where maintaining a constant bit rate is essential, such as video conferencing or live broadcasting, as it ensures consistent playback quality despite varying network conditions. On the other hand, VBR excels in applications where video quality and file size optimization are key considerations. This makes VBR an excellent choice for online streaming platforms, video distribution services, and media content with varying complexities. Ultimately, the decision between CBR and VBR will depend on the target audience, the platform of delivery, and the desired balance between consistent bit rates and varying video quality to deliver the best possible viewing experience.

Do you have a music CD and copy it to output in MP3, AAC, WMA, etc.? Or do you just need to convert one file format to another? In this case, we recommend reading this comparison between CBR and VBR first.

First we learn what exactly these abbreviations mean. It would also be useful to know their functionality, the significant difference between these file formats and encoding methods.

Important:

Please note that the terms CBR and VBR represent different aspects. For example, CBR for comic files saved on CDisplay and VBR for the volume boot record. However, you should know that none of these terms describe what we explain in this article comparison between CBR and VBR.

Coding of the CBR file format

CBR is the abbreviation that describes the term “constant bit rate”. In fact, it is an encoding method that allows the file bit rate to be maintained without changes. In the event that audio data is encoded (this is done by the codec), the file uses a fixed value for its bit rate. For example, the bit rate would be approximately 128 Kbit / s, 256 Kbit / s or 320 Kbit / s.

The most notable advantage of the CBR file format is that it offers faster data processing. This means that when comparing CBR and VBR in terms of data processing speed, CBR wins. However, when it comes to Quality Score, CBR output files don’t offer a better optimization. Again, VBR is better if CBR is compared to VBR in terms of quality. In short, it’s basically about choosing quality instead of speed, or vice versa.

If you need to stream multimedia files, CBR can be seen as a useful option. Suppose your connection supports only a certain bit rate (e.g. 320 kbit / s) for steam streaming. In this case, a constant bit rate (300 Kbit / s) or less makes sense. Compared to a format that constantly changes the bit rate during transmission, a format with a constant bit rate is better. If the bit rate exceeds the compatible bit rate value of the respective network, the transmission is interrupted. Therefore, it makes more sense to have a CBR file when it comes to activities like online streaming.

Encoding of the VBR file format

The abbreviation VBR refers to the term “variable bit rate”. Well, the term itself indicates its functionality. You just have to understand the difference between the terms “constant” and “variable”. In other words, the constant bit rate and the variable bit rate are concepts with exactly opposite meanings. VBR is an encoding method that increases or decreases the bit rate of audio files as needed. There is a target area when it comes to bit rates. For example, the range can be between 65 kbit / s and 320 kbit / s. VBR supports audio file formats such as MP3, WMA, OGG and many other formats.

VBR file formats have a special sound quality function compared to the file size ratio. In fact, this is the main advantage of VBR files over CBR. Because of this aspect, it is possible to get smaller files to match the quality of the video. For example, if the original sound quality of the file is low enough, VBR will resize the file. This way, low quality files are lightweight and high quality files do the opposite.

Under the VBR mechanism, the file bit rate for inaudible segments is significantly reduced. What about the more complex parts of the track (where there is a mix of frequencies)? Well, the bit rate of these segments automatically increases to a maximum of 320 kbps. Therefore, the sound quality is preserved in areas where this is absolutely necessary. Overall, this is a great way to get a relatively small file capacity while maintaining quality. All in all, you need less space to store VBR files than CBR.

The main disadvantage of VBR, however, is a compatibility problem. With floating bit rates in the encoding process, VBR is considered a more complex file format. As a result, this file format may not be compatible with some older devices. On the other hand, CBR files are compatible with practically all devices, including older ones.