MP3 Bitrate Calculation Methods

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MP3 Bitrate Calculation Methods

What is MP3 Bitrate?

MP3 bitrate is the amount of data that is used to encode an MP3 audio file. The higher the bitrate, the higher the quality of the audio file. However, higher bitrates also result in larger file sizes.

How is MP3 Bitrate Calculated?

MP3 bitrate is calculated using a variety of factors, including the complexity of the audio signal, the desired quality of the audio file, and the target file size.

What are the Different Types of MP3 Bitrate Calculation Methods?

There are two main types of MP3 bitrate calculation methods:

Constant bitrate (CBR): This method uses a constant bitrate for the entire audio file. This results in a consistent audio quality throughout the file, but it can also result in larger file sizes for complex audio signals.
Variable bitrate (VBR): This method uses a variable bitrate, which means that the bitrate changes depending on the complexity of the audio signal. This results in smaller file sizes for complex audio signals, but it can also result in a slight variation in audio quality.

Which MP3 Bitrate Calculation Method is Best?

The best MP3 bitrate calculation method depends on your needs. If you need a consistent audio quality throughout the file, then CBR is the best option. If you are more concerned about file size, then VBR is the best option.

How to Choose the Right MP3 Bitrate for Your Needs

When choosing the right MP3 bitrate for your needs, you should consider the following factors:

The type of audio signal: Complex audio signals, such as those that contain a lot of high-frequency content, require a higher bitrate than simple audio signals.
The desired quality of the audio file: If you want the highest possible quality, then you should use a higher bitrate. If you are more concerned about file size, then you can use a lower bitrate.
The target file size: If you have a specific file size in mind, then you can use a bitrate calculator to determine the bitrate that you need.

Conclusion

MP3 bitrate is an important factor to consider when encoding audio files. By understanding the different types of MP3 bitrate calculation methods and how to choose the right bitrate for your needs, you can ensure that your audio files sound great and have a reasonable file size.

Here are some additional details about the different types of MP3 bitrate calculation methods:

Constant bitrate (CBR): This method is the simplest to understand and implement. It is also the most reliable, as it ensures that the audio quality is consistent throughout the file. However, it can result in larger file sizes for complex audio signals.
Variable bitrate (VBR): This method is more complex than CBR, but it can result in smaller file sizes for complex audio signals. This is because VBR allows the encoder to use a lower bitrate for less complex parts of the audio signal, and a higher bitrate for more complex parts of the audio signal. However, VBR can result in a slight variation in audio quality, depending on the complexity of the audio signal.

Ultimately, the best MP3 bitrate calculation method for you depends on your specific needs. If you need a consistent audio quality throughout the file, then CBR is the best option. If you are more concerned about file size, then VBR is the best option.

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The bitrate and its relationship with the audio quality in an MP3

The bitrate is a measure of the amount of audio information that is encoded per second in a compressed audio file, such as an MP3. Bit rate is measured in kilobits per second (kbps).

The higher the bitrate, the higher the audio quality. However, a larger file size will also be required to store the same amount of audio time. Therefore, it is important to choose a suitable bitrate to balance quality and file size.

For music files, a bitrate of at least 128 kbps is recommended for decent sound quality. However, if you want higher sound quality, you can go for a higher bitrate, such as 256 kbps or even 320 kbps.

For voice audio files, a bit rate of 64 kbps is sufficient for clear sound quality. However, if you want higher sound quality, you can go for a higher bitrate, such as 96 kbps or 128 kbps.

In short, bitrate is an important factor in the audio quality of an MP3 file. It is important to choose a suitable bitrate to balance quality and file size.

Also, it’s important to note that bitrate isn’t the only factor that affects the audio quality of an MP3. Other important factors include the sample rate and the number of channels. The sample rate refers to the number of times the sound is measured per second, while the number of channels refers to the number of audio channels in the file.

For example, an audio file with a bit rate of 128 kbps and a sample rate of 44.1 kHz and 2 audio channels will have higher sound quality than a file with the same bit rate but a sample rate of 22 kHz and 1 audio channel.

In conclusion, if you want to get the best audio quality from an MP3 file, it’s important not only to choose a suitable bitrate, but also to consider the sample rate and number of channels. It is advisable to choose an optimal combination of these factors to obtain the best sound quality.

In addition, it is important to mention that there are other audio formats, such as WAV, FLAC, AIFF, which, unlike MP3, are not compressed, which means that they do not lose audio quality to the compression process. However, these formats often have much larger file sizes than compressed formats like MP3.

So, if you want the best audio quality, it’s recommended to use uncompressed formats like WAV or FLAC, but it’s also important to consider storage space and compatibility with different devices and audio players. In case of opting for compressed formats, it is important to choose an appropriate bitrate and take into account other factors such as the sampling frequency and the number of channels.

In summary, bitrate is an important factor in the audio quality of an MP3 file, but it is not the only factor to consider. It is important to choose a suitable bitrate, as well as take into account the sample rate and the number of channels to obtain the best sound quality. In addition, there are other uncompressed audio formats that offer higher sound quality, but also have a larger file size.

Why are MP3 bitrates often multiples of 32? (power of 2)

Some people say:

I understand why multiples of 2 often show up on computers since they are binary, but I can’t figure out how the most common mp3 bitrates (64kbps, 128kbps, 160kbps, 192kbps, 256kbps, 320kbps, etc.) also tend to follow this rule.

Since MP3 is just a sequential encoding of sound waves, why is it important to represent each second in kilobits divisible by 2?
Does a music player like iTunes continue to read the file and play the encoded sound regardless of the second limit, or does it read the file every second?
In the latter case, reading a 256kbps file requires reading slightly fewer memory pages than a 257kbps file, but the player can always read 256KB chunks, regardless of their bitrate, and just process them automatically. incremental, right, Bar?
Are 128kbps MP3 songs popular simply because it’s a generally accepted bitrate, or do they really have any advantages over 126kbps and 131kbps files, apart from a very slight difference in quality/file size?

For constant bit rate (CBR) encoding, the MPEG-1 Audio Layer III standard specifies standard bit rates of 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256 and 320 kbit/second. There are a few others defined in the MPEG-2 standard, but they are also multiples of 2 (actually all multiples of 8 in the range 8 to 160 – see the table called “Bitrate Index” in the link above) .

Technically, there is nothing that limits the MP3 bitrate to a multiple of 2, since variable bitrate encoding can be used, or a custom bitrate can be achieved using some flags not used in the MPEG specification ( although this must be implemented manually). . In order for MP3 to be MPEG-compliant, and therefore compatible with most MP3 decoders, it must have a bitrate defined by the specification, so all CBR-encoded MP3 files have a bitrate of two.

What is a good bitrate guide for mp3 files?

(a good bitrate guideline for mp3 files?)

MP3 files are compressed audio files created from audio formats such as wave (.wav). Wave files replicate analog recordings and digital sound files at the expense of large file size, while MP3 files sacrifice some quality for a smaller footprint. There are several factors that mitigate the quality sacrifice during the conversion process. With the correct bitrate and settings, MP3 files can provide very high quality results, making them very close to the original wave files when played on portable audio players.

An mp3 player.

The balance between file size and quality is somewhat subjective. For audiophiles, any difference is noticeable. Others may simply not be able to tell the difference between a high quality MP3 file and a raw wave source. In many cases, the nuances of the sound environment will only become clearer when played through a high-quality stereo system.

MP3s are compressed digital music files that sacrifice quality for file size.
MP3 files are primarily targeted at portable audio players. In this field, high-quality MP3 files are played with incredible sound due to their small file size. With the limited memory of portable players, it makes sense that one would want MP3 files to be as small as possible while maintaining the highest possible quality.

For this, one of the most important factors when creating MP3 files is the bit rate. In general, the more bits per second that are preserved from the original file, the higher the quality of the MP3 and the larger the file size. Lower bit rates reduce size and quality. The idea is to use the bitrate for maximum realism without saving unnecessary data, which just creates larger files with no noticeable difference to the ear.

For voice recordings such as lectures or language lessons saved to waveforms, a bit rate of 32 kilobits per second (kbps) is acceptable, although 64 kbps may offer better quality, depending on the source. At 32 kbps, the sound may sound “flat”, but that’s understandable. A 64 kbps MP3 file created from a voice recording should sound nearly identical to the original.

Desaturated acoustic music with simple arrangements should work fine at 192kbps bitrate. You can choose 256 kbps if the music will be played on a high quality device. Music that falls into this category includes folk, boy band songs, easy listening, and folk music. There are also works by many classic artists such as James Taylor, Linda Longstadt, Jonny Mitchell, and Simon Garfunkel.

What is bit rate? Knowledge of the MP3 audio format.

Digital audio formats are audio signals that are recorded, processed, and reproduced in digital form.

The emergence of digital audio formats is to meet the needs of high-fidelity playback, storage and transmission. Simply put, early analog audio formats had issues with playback distortion and glitches due to media wear. Since the advent of the CD, digital format audio files have become popular, but another problem has arisen: the limitation of the storage volume, and the CD still has the phenomenon of wear. Saving to hard drive (relatively longer storage time) is not a good solution when storage media (mainly hard drives) are still expensive at the time. The rise of the Internet has created a requirement for long-distance file transmission. Under the restriction of bandwidth, the demand to reduce file size has become more intense. All this has led to the generation of lossy compressed digital audio formats from external factors!

In terms of internal factors, with the improvement of computing and coding capabilities, the progress of various acoustic psychological models has promoted the emergence of various lossy compressed digital audio formats. Some of the most commonly used audio formats in MP3 players are briefly introduced below: MP3 (CBR, VBR, ABR), WMA, WAV, ADPCM, and the emerging audio formats AAC, ASF, and OGG.

Before introducing various digital audio formats, let’s clarify one concept: bitrate.

In the field of computing, all information is digitized. Bit is the smallest unit of data in a computer, it refers to a number of 0 or 1, which is a mathematical binary number, a “0” or “1” , is a bit. For example, when we say a 2-digit number, it means that it is a two-digit binary number, and there are 4 combinations of “00”, “01”, “10” and “11”, which represent 0, 1, 2 and 3 is four numbers.

What is the capacity of the high resolution sound source?

Hi-Res audio

High resolution sound source with more information than conventional CDs.

HiRes Audio

Since the data size is large, you can enjoy high-quality sound with a three-dimensional effect, but the problem is that when managing multiple high-resolution audio sources, the required storage capacity becomes huge.

Then I will introduce what is the capacity of the high resolution sound source, including the management method.

What is the capacity of Hi-Res Audio sources compared to CDs?
In determining the capacity (file size) of a high-resolution sound source, the sampling frequency and bit depth of the sound source are important factors.

The sample rate (sample rate) is a numerical value that is used as an index when converting analog data, such as speech, to a digital signal.

It indicates how many times per second an information sample was measured, and is expressed in “Hz (hertz)”.

If sampling is done every 44,100 seconds, it will be “44.1 kHz”.

On the other hand, the bit depth is a numerical value that indicates how many pieces are recorded in each divided data.

It is represented by “bit”.

Both the sample rate and the bit depth mean that the higher the number, the more information there will be, that is, the higher the resolution.

The amount of music data per second is called the bit rate.

Bit rate is the sample rate multiplied by the bit depth and is expressed in “bps”.

The calculation formula is as follows.

Bit rate (bps) = sample rate (Hz) x bit depth (bit) x 2

For example, the bit rate and sample rate of a CD sound source are generally “44.1 kHz / 16 bits”.

Most so-called “CD sound quality” sound sources are based on this number.

The size of the 5 minute 44.1 kHz / 16 bit / sound source file is about 50 MB.

But what about hi-res audio sources?

High resolution sound source capacity per song (5 minutes) varies depending on the music data format, as shown below.

WAV: 192 kHz / 24-bit: capacity for 5 minutes is 330 MB
FLAC: 192 kHz / 24 bit: capacity for 5 minutes is 200 MB
ALAC: 192 kHz / 24 bits: capacity for 5 minutes is 200 MB
What you can see from this is that the capacity of the high resolution sound source is 4 to 6 times that of the CD sound source in 5 minutes.

Large capacity high resolution music management equipment
If you download 5 high-resolution songs for 4 minutes, it will take up about 700MB (for 96kHz / 24-bit WAV files).

In the case of 10 songs, it exceeds 1400MB, that is, 1GB.

If so, I would like to have enough storage to handle that amount of data.

An effective way to do this is to build a NAS-centric network audio system that incorporates a large-capacity hard drive.

For example, if you can prepare a 4TB (terabyte) hard drive, it can store around 20,000 high-resolution songs.

Next, we will explain what NAS and network audio are like.

NAS
NAS stands for “Network Attached Storage” and it reads like aubergine.

It stands for network attached storage, and it is also called a network hard drive or network compatible HDD.

In other words, it is an external hard drive that is used when connecting to a network (LAN).

A normal external hard drive used when connecting to a PC = PC via USB etc. can basically be used with only one PC.

However, if it is a NAS, it can be used with multiple devices participating in the LAN.

Files saved on the hard drive can also be used and shared from, for example, the personal computers of each family member participating in the home LAN, smartphones connected via Wi-Fi, and TVs in the living room to be.

It is also possible to access the data on the NAS from the outside via the Internet.

The NAS is often used in the home to store and share data for music, video (video / TV recording data), photos (images), etc.

Meaning and relationship of sample rate, bit depth, and bit rate

bit depth

Sampling rate
Bit depth
Bit rate

bit depth audio

I will present the three meanings and relationships of.

Table of Contents
What is the sampling rate?
What is bit depth?
What is a bit rate?
resume
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What is the sampling rate?
For example, let’s say you say “Ah” for 1 second.

When recording this “Ah” sound on a personal computer, the “Ah” sound is divided into tens of thousands per second, each divided into tens of thousands.

“The height of this section was about this.”
“The length of this section was about this.”
Record it as data like this.

The personal computer continually reads each of this divided data and outputs it as a “voice” called “Ah”.

At this time, “how many tens of thousands of sounds are collected per second” is called the “sample rate.” (Also called “sample rate”)

Sampling rate
▲ Sample rate image

The more divisions you make, the smoother the sound will be, and as a result, you will feel that the sound quality has improved!

What is bit depth?
The sample rate is “how many tens of thousands of sounds are collected per second”.

“How much capacity is given to each divided data (sample)” is called “bit depth”.

Figure_bit depth
▲ Bit depth image

Also called “number of quantization bits”, “number of sample bits”, “bit offset”, and so on.

For example, if the bit depth is “16 bits”, the amount of information is 2 to the 16th power (65536) for one sample.

The higher the bit depth, the greater the expressiveness of the sound’s fineness and volume, and as a result, I feel like the sound quality has improved!

By the way, the bit depth of most of the world’s sound sources is 16 bit.

that’s why

“Import music from CD!”
“Import music downloaded from the Internet!”
In such cases, 16 bits is sufficient.

On the other hand, if you say “What you recorded in your DAW comes out wav!”, It is better to have 16 bits or more.

This is because, for example, when processing audio effects with audio editing software, sound deterioration can be reduced to zero by assigning an additional bit depth (for example, 32-bit). (Although 16 bit is fine for final output)

What’s more,
note that “bit depth” on this page has a different meaning than “bit depth” in video.

Reference: What is Bit Depth (Color Depth)? Differences like 10bit / 24bit / 30bit

What is a bit rate?
Bit rate is the “amount of data per second”.

Reference: What is a bit rate? Relationship between image quality, sound quality and codec [Video / Audio]

The “sample rate” and “bit depth” presented above are

Sample rate: how many tens of thousands of sounds are collected per second
Bit depth: how much to give to each divided data
Therefore, the product of these two values is the “bit rate”.

Audio encoding

Audio Encoding

I wrote over audio files last time, but if you reduce the file size (code at a lower bit rate), the sound quality tends to deteriorate. How much should it really be? .. ..

audio encoding

When compressing using audio encoding (AAC, MP3, etc.), the compression rate is determined by the bit rate at the time of encoding. Specifically, if you set a low bit rate, the compression rate will be higher and the file size when saved will be smaller, but first of all, what is the bit rate for uncompressed original sound source (PCM) ?
If you save it as PCM, the sound quality will be that of the original sound, but it can be a bit awkward to save without worrying about the file size. Also, depending on the application, I think the memory capacity is sufficient even for the original sound size and the communication speed is fine. Therefore, I would like to write about the sample rate and bit rate that are often heard in digital audio.

The bit rate of digital audio is determined by the sampling frequency, the number of bits assigned to a sample (number of quantization bits), and the number of channels (stereo, monaural, etc.).

PCM bit rate (uncompressed) = sample rate x number of quantization bits x number of channels
As I wrote a bit last time, in file containers like wav and mp4 format, this information is attached as a header, so that the application can see the header and play it back. The compression rate of the encoding is determined by the bit rate specified at the time of encoding for this PCM (uncompressed) bit rate.
For example, as many of you know about music CDs, with 44.1 kHz stereo, this is the next bit rate.

Music CD bit rate: 44100Hz x 16bit x 2ch (stereo) = 1411.2kbps
When encoding this with MP3, AAC, etc., it is natural to specify a bit rate lower than 1,411.2 kbps. For example, when encoding at 256 kbps, the compression rate is around 18% when the original sound is 100% and the file size is 1/5 or less.

Encode a music CD at 256 kbps: 256 kbps / 1,411.2 kbps = about 18%
In general, the sample rates of audio devices connected to PCs are 48 kHz and 44.1 kHz for music, 16 kHz and 8 kHz for audio such as microphones and headphones, and 32 kHz, 24 kHz, 22.05 kHz. , etc.

The bit rate of PCM (uncompressed sound source) with 16-bit quantization bits is as follows.

Stereo (for music) PCM 16-bit bit rate (example)
Sampling frequency Number of quantization bits Number of channels Bit rate Comments
48kHz 16 16 2 1536 kbps
44.1 kHz 16 16 2 1,411.2 kbps Music CD
32kHz 16 16 2 1,024 kbps
24kHz 16 16 2 768 kbps
22.05 kHz 16 16 2 705.6 kbps
Monaural (for audio) PCM 16-bit bit rate (example)
Sampling frequency Number of quantization bits Number of channels Bit rate Comments
32kHz 16 16 1 512 kbps Super Wide Band
24kHz 16 16 1 384 kbps
16kHz 16 16 1 256 kbps broadband
8kHz 16 16 1 128 kbps Narrow band

Sampling rate
If you check the web, there are explanations such as the sampling required to convert analog waveforms to digital conversion. For example, it shows how many samples of an audio signal input from a microphone are taken per second and digitized. The larger the sample, the greater the range that can be recorded. When an analog waveform is digitized, the frequency that can be expressed is half the sampling frequency (sampling theorem). For example, with a sample rate of 48kHz, it is possible to express up to 24kHz. At 8kHz (narrowband) and 16kHz (wideband), which are often used for audio, you can only hear up to 4kHz and 8kHz, respectively. The higher the sample rate, the higher the bit rate.

sampling theorem
It is a very simple explanation, but it can express up to half the sample rate. When sampling a signal, if the interval is small, it can be restored close to the original signal, but if it is too thick, it cannot be restored (I would like to write a little more detail when talking about signal processing or other time ).

What is the bit rate? Simple explanation

bitrate

Bit rate is a unit of data transfer.

When used in video or audio, as in video editing, it indicates how much data is represented per unit of time, and “bits per second (bps)” is generally used.
A bit is the smallest unit of data that a computer handles.
Two states of “0” and “1” can be expressed by 1 bit. (1 binary digit)
Similarly, a byte representing the size of a file is a unit of data handled by a computer. (1 byte = 8 bits)
Here are some things to keep in mind about bit rates.
In home appliance hard disk recorders, it is sometimes expressed as a recording mode such as XP, SP, LP.
The higher the bit rate value (numerical value), the better the picture and sound quality, but the greater the amount of data (file size).
The unit of bit rate is usually Mbps, which means 10 6 (10 to the sixth power) for video, and kbps, which means 10 3 (10 to the third power) for audio.
When burning a video to DVD, there is a limit to the amount of data that can be burned to DVD, and if you try to burn a long video, you will have to lower the bit rate, resulting in poor image quality. . To record high-quality video, the bit rate must be increased, which increases the amount of data required and shortens the recording time.
Even if the bit rate used is the same, the image quality and sound quality will differ depending on the encoder and compression method used for digitizing.

What are “bit depth” and “sample rate”? Part 2

Understanding Sample Rate, Bit Depth, and Bit Rate - Headphonesty

What is the sample rate?

Bit Depth

Next, I will explain the sample rate.

The sample rate is like the “resolution” of the audio.

The higher the sample rate, the more samples per second = you can hear better.

Requires double sample rate

One thing to keep in mind here is that you need twice the sample rate to hear sound at that frequency.

For example, if you want to hear a 1000 Hz (1 kHz) sound accurately and clearly, the sampling frequency must be at least 2000 Hz (2 kHz).

If the sample rate is less than twice the value you want to hear, “aliases” will occur and you will not be able to process the sound accurately, such as crackle or noise.

Nyquist frequency

By the way, to use a little technical word, it also means not to exceed the “Nyquist Frequency”.

The Nyquist rate is exactly half the supported sample rate.

For example, if the sampling frequency is 44.1 kHz, the Nyquist frequency will be 22.05 kHz.

If you try to handle this high-pitched sound that exceeds 22.05 kHz, the above-mentioned “aliasing” will occur and you will not be able to reproduce the sound correctly.

Range recognizable by the human ear

The loudest sound that can be recognized by the human ear is said to be 20 kHz, so to hear a 20 kHz sound, you only need to have a sample rate of at least 40 kHz.

After that, to avoid aliasing, apply an anti-aliasing filter until the Nyquist (Transition Band) frequency is reached.

For 44.1 kHz, 2050 samples x 2 are required.

In other words, a sample rate of 44.1 kHz is all that is needed to minimize the limit of sound (20 kHz) that the human ear can hear.

When the sampling frequency is high (96 kHz, 192 kHz)

Recently, it can be set to a high sample rate, such as 96 kHz or 192 kHz.

Unfortunately, even with such a high sample rate, it’s hard to tell the difference.

As shown in the image above, non-human animals can hear higher frequency sounds.

However, it is a level that we do not have to worry about because it is a completely inaudible zone for the human ear.

By the way, many audio interfaces cover up to 192 kHz.

Controversy over sampling rate

In fact, in the 1970s, many media outlets were controversial about sample rates.

At the time, 48 kHz was the audio standard used in radio, television, and video work.

However, broadcasting stations have decided to use 44.1 kHz as a standard to prevent data from being copied to consumers (viewers) by intentionally breaking compatibility (or making conversion difficult) …

It’s difficult to change data from 44.8 kHz to 44.1 kHz, so it prevented the average viewer from converting it to the sample rate used for home devices.

By the way, the article “Comparison of professional versus cheaper audio interface” is summarized here, which is also explained from the point of view of bit rate and sample rate.