twitch bitrate Archives

What is the code rate?

What is the bit rate for? What is frame rate? What is the resolution?

Students often ask, what is the code rate? What is the bit rate for? What is frame rate? What is the resolution?

This problem of not being able to speak clearly, listening and not understanding has worried many beginners.

Today Ben Shuai specially came to solve these professional terms for you.

frame

In the video, do you know what the unit less than a second is?

That’s right, it’s what I’m going to talk about today: “framework”!

Frame: It is the smallest unit in video animation and countless frames constitute seconds.

Simply put, one frame equals one image, and a second is made up of a certain frame, that is, a certain number of images!

Play the images continuously and you will see dynamic images under the influence of the visual residue produced by your eyes.

The more frames per second, the smoother and more realistic the images we see!

We also call the number of frames in 1 second the number of frames, usually expressed in fps (FramesPer Second).

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Bit rate

Bit rate refers to the number of bits (bit) transmitted per unit of time, in bps (bit per second).

Bit rate is also known as “binary bit rate”, commonly known as “code rate”. Indicates the number of bits transmitted per unit of time. It is used to measure the transmission speed of digital information, often written as bit/sec. According to the number of bits occupied by each image storage frame and the transmission bit rate, the digital image information transmission speed can be calculated [1].
In modern digital communication, the transmission volume of digitized video and other information is large, so it is often measured in kilobits per second or megabits per second, which are written as kbit/sec (or kbps) and Mbit/sec. (or Mbps respectively). ). For example, the amount of information digitized from an ordinary color TV signal can reach 216 Mbit/sec. A good digital broadcast channel can transmit dozens of color TV programs, and its capacity can reach several gigabits or gigabits per second (written as Gbit/sec or Gbps) [1] .
Bitrate is often used to measure the quality of video files.
Bitrate is often used to measure the quality of video files.
flexibility edit stream
Because each network is unique and each access line has different conditions (such as length, attenuation, crosstalk environment, etc.), access lines from different telephone companies must support different data rates. For ADSL and VDSL modems, it is best to set the data rate to one of many possible data rates. For example, DMT-based ADSL and VDSL can theoretically change the tariff at fine intervals, and CAP-based RADSL (Rate Adaptive ADSL) also provides some flexibility in tariff configuration [2].
However, telephone companies may want to limit xDSL service to a small set of rates sufficient to provide a variety of services. If a limited set of tariffs can be adapted to a wide range of services, then the management of the services in this case is simpler than in the case of variable tariffs. Telephone companies want the choice of modem speed to be under the control of the network, not the user [2] .
In this mode, the selection of the transmission rate set of the xDSL network must be prudent. In this case, there is a possibility that two adjacent systems receive traffic at very different rates and the system must be able to handle such a situation. The other model, the “best match” approach using adaptive rate ADSL (similar to a voiceband modem), is more beneficial to new network operators and Internet Service Providers (ISPs) [2] .
Transmission control method
Most bit rate control schemes consist of two parts. Part of the encoded bit stream output by the encoder is fed into a buffer. For a constant bitrate channel, the data in the buffer is fetched at a constant rate, and if the buffer is large enough, the bitrate variation caused by the MPEG picture type, etc. can be smoothed out. This is necessary for both constant bit rate transmission and variable bit rate transmission in general. However, in practice, the buffer size is always limited. The buffering process will bring a delay to the system, and this delay is proportional to the size of the buffer. Latency is often a serious issue for real-time image communication, so buffers should be kept as small as possible. That is, long-term fluctuations in bitrate due to changes in scene content or changes, etc. they cannot be softened in this way, so another part is needed. This is to send some measure of the output bitrate to the encoder to control the encoding process, thus changing the output bitrate [3] .

What does MP3 bitrate mean?

Bit rate

The rate at which a digital channel transmits digital signals is called the data transfer rate or bit rate.
The word bitrate has many translations, such as bitrate, etc., which indicates how many bits per second the encoded (compressed) audio data should be represented, and a bit is the smallest binary unit, either 0 or 0. 1. The relationship between bitrate and audio and video compression is simply that the higher the bitrate, the better the quality of the audio and video, but the larger the encoded file; if the bitrate is lower, the situation is reversed.

For example: encode audio and video at 500 Kbps.
where bps are bits 1K = 1010 = 1024
b is little
s is the second
p is for (for)
Therefore, encoding at 500 kbps means that the encoded audio and video data must be represented at 500 K bits per second.
In the baseband transmission system, the bit rate is used to represent the code rate of transmitted information.
The bit rate Rb refers to the unit of time
The number of binary bits transmitted within the unit, the unit is b/s. For example, the transmission speed of a computer serial port is up to 115200b/s.
The symbol rate or baud rate Rs refers to the number of modulation symbols transmitted per unit of time, that is, ternary and ternary
The information transmission rate of the multivariate digital code stream in the

In M-ary modulation, the relationship between the bit rate Rb and the baud rate Rs is:
Rb=Rslog2M
The sampling rate refers to the ratio of the sampling samples to the total number of samples, and the sampling rate refers to the number of samples per unit of time. If it is an instrument, the sampling rate is 40MSa/s, which indicates that the number of samples per second is 40M, but it cannot be represented by 40MHz.

The process of converting analog audio to digital audio is called sampling. In a nutshell, how much data is needed to record a 1 second duration of sound via waveform sampling. A sound with a sample rate of 44 KHz requires 44,000 data points to describe a 1-second sound waveform. In principle, the higher the sample rate, the better the sound quality.

Quality (bit rate)

In multimedia technology, quality is often used to judge the effect of audio, and quality here is actually bitrate.

1. Introduction
2 sound control
3 encoding mode
Introductionedit transmission
The term quality is widely used.
In multimedia technology, quality is often used to judge the effect of audio, and quality here is actually bitrate.
On WINDOWS it is called “bit rate” and on some players it is described as ” bit rate “.
Quality refers to the bit rate at which digital sound is converted from analog to digital format. The higher the bitrate, the better the quality of the restored sound.
sound control edit stream
16 Kbps = phone quality
24 Kbps = increase phone quality, shortwave transmission, longwave transmission, European standard medium wave transmission
40 Kbps = American standard medium wave transmission
56Kbps=Voice
64 Kbps = boost voice (best bitrate setting for cell phone ringtones, best setting for cell phone mono MP3 players)
112 Kbps = FM stereo broadcast FM 128 Kbps = tape (best setting for mobile phone stereo MP3 player, best setting for low-end MP3 player)
160 Kbps = HIFI high fidelity (best setting for mid to high end MP3 players)
192Kbps=CD (best setting for high-end MP3 players)
256Kbps=Studio Music Studio (for music enthusiasts)
In fact, with the advancement of technology, the quality of music is also getting higher and higher, the highest quality of MP3 is 320Kbps, but some formats can achieve higher sound quality.
For example, the emerging APE audio format can provide real audiophile level lossless sound quality and smaller volume than WAV format, and its quality is usually 550kbps-950kbps.
encoding modeedit stream
VBR (Variable Bitrate) Dynamic Bitrate means there is no fixed bitrate. The compression software immediately determines which bitrate to use based on the audio data being compressed. This is a method that takes quality as a premise and takes file size into account The recommended encoding mode;
ABR Average Bit Rate (Average Bit Rate) is an interpolation parameter of VBR. LAME created this encoding mode in response to the low file volume ratio of CBR and the variable size of files generated by VBR. Within the specified file size, ABR takes every 50 frames (about 1 second for 30 frames) as a segment. High-frequency and insensitive frequencies use relatively low traffic, and low-frequency and large dynamic performance use high traffic, which can be used as VBR and CBR, a compromise option.
CBR (constant bitrate), constant bitrate means the file has one bitrate from start to finish. Compared to VBR and ABR, the compressed file size is very large and the sound quality will not improve significantly compared to VBR and ABR.

What is bit rate? Knowledge of the MP3 audio format. Part 2

Bitrate is a benchmark indicator of the efficiency of digital music compression.

The bit rate represents the number of bits bps (bit per second, bits per second) transmitted per unit of time (1 second). We usually use kbps (in simple terms, it is per second) clock 1000 bits) as the unit. The bit rate of digital music on CD is 1411.2 kbps (ie recording 1 second of CD music requires 1411.2 × 1024 bits of data). The higher the bit rate of the music file, the more data (Bit) must be processed in a unit of time (1 second), and the better the sound quality of the music file. However, when the bit rate is high, the file size increases, which will occupy a large amount of storage capacity. 8 to 320 kbps.

1. WMA (Windows Media Audio, Windows Media Audio)

As a Microsoft media compression method, it is a part of the technology that compresses only audio data in Windows Media Technologies. The sound quality is similar to MP3 and can be compressed with half the technology of MP3. It has the copyrighted Windows Media Rights Manager, which can be played by installing in WMP (Windows Media Player, Windows Media Player). Due to the strong influence of Microsoft and Windows, as well as major copyright reasons, the major American record companies EMI and BMG have officially confirmed that they use the WMA method developed and produced by Microsoft. It is believed that this advanced method will become even more popular in the future.

2. MP3 (CBR, VBR, ABR)

MP3 is currently the most widely used and widely used lossy compressed digital audio format, which has been explained above and will not be repeated here.

CBR (constant bit rate)

CBR is the oldest and simplest MP3 encoding (compression) method. When this method is used for encoding, the bit rate of the entire file is the same, in other words, the bit rate used by the MP3 file per second is the same. Although the music file has sections of varying complexity, the encoder always keeps the bit rate constant, unless you use the highest sound quality, otherwise the sound quality of the different sections of the MP3 file will vary. The more complex the passage, the worse the sound quality. Its biggest advantage is that the file size is fixed, which is convenient for calculating storage space.

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 CD discs, audio files in digital format have become popular, but another problem has arisen: the limitation of storage volume and the phenomenon of CD disc wear is still present. Saving to a hard drive (in connection with longer storage time) is also 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, “11” in decimal respectively. 1, 2 and 3 are four numbers.

Difference between CBR (fixed), VBR (variable) and ABR (average) [bit rate]

constant vs variable bit rate

CBR (constant bit rate)
VBR (variable bit rate)
ABR (average bit rate)
There are three types.

I will present the differences between them.

See the following article for the “bit rate”.

Reference: What is a bit rate? Relationship between image quality and sound quality [Video / Audio]
Related: Difference Between VFR (Variable) and CFR (Fixed) [Frame Rate]

Every feature
I will briefly explain each feature.

CBR (constant bit rate)
CBR (constant bit rate) is

A video with a constant video bit rate.

for instance,

Scenes with intense movement
Scenes with complex audio
Even in “scenes that require a large number of bit rates”, for example, the bit rate to be assigned is constant and

Motionless scene
Scene without audio
Even in “scenes that do not require a lot of bit rate”, the bit rate to be assigned is constant.

In this way, a video that assigns a constant bitrate to “Assign a constant bitrate!” In any scene it is called CBR (constant bit rate) video.

The following are the characteristics of CBR.

(○) Search (fast forward / rewind) is fast
Since the transfer rate is the same, you can search instantly.
(○) File size can be predicted
If you decide beforehand to “encode at XX bit rate”, you can predict the file size from resolution, frame rate, video length, codec, and so on.
(○) Easy to use as a material
In the case of video, there is no need to worry so much, but in the case of the sound source, various problems can occur such as drift of sound with VBR or ABR (so if there is a possibility that it will be used later to video edit material, etc. Better to encode with CBR)
(○) Fast encoding speed
It doesn’t change much, but unlike VBR and ABR, you don’t need to “predict” it, so encoding is faster.
(X) Image quality and sound quality are not very good for the file size
Even a monotonous scene that does not require a lot of bit rate allocation may be assigned a certain number, or a scene that requires a large bit rate may not have enough bit rate, so the image quality and sound quality for the file size. Cospa is bad
VBR (variable bit rate)
VBR (variable bit rate) is

A video whose bit rate varies depending on the scene.

VBR_figure

for instance,

Scenes with intense movement
Scenes with complex audio
In “scenes that require many bit rates”, such as assigning many bit rates and

Motionless scene
Scene without audio
For “scenes that do not require a lot of bit rate”, assign a lower bit rate.

In this way, a video that assigns only the required bitrate according to the scene, “You need this bitrate, don’t you?” It’s called VBR (Variable Bit Rate) video.

The following are the characteristics of VBR.

(○) Image quality (sound quality) by file size is the best
Compared to CBR and ABR, the image quality (sound quality) by file size is the best.
(△) Unpredictable file size after encoding
The file size cannot be predicted because the bit rate fluctuates extremely depending on the content of the material to be encoded. (However with the x264 encoder etc it is possible to predict because it puts an upper limit on the file size and allocates the maximum bit rate within that range)
(X) Old MP3 players may not play well
If you have an old MP3 player, the playing time display may be strange, the bit rate display may be strange, or you may not be able to play from beginning to end.
(X) When used as video editing material, it may cause sound drift.
For more information, see the following article
Reference: Causes and countermeasures for sound deviation [Encoding]
If you want to encode video with high image quality and low capacity, VBR is your choice.

By the way, in VBR, it is common to determine video quality by “quality standard” (CRF value in x264 encoder) rather than by “bit rate standard”.

For example, instead of saying “Encode at 192bps!”, Specify something like “Encode at

What is a bit rate?

Audio Bit rate

The bit rate in a video is “how much information is packed in one second”.

BIT RATE

What if the bit rate is high?
Basically, the higher the bit rate, the better the picture and sound quality.

* Although it is closely related to the “codec” described later, it will basically improve.

There are two types of bit rates
Bit rates are assigned separately for “video” and “audio”.

The higher the bit rate assigned to “video”, the better the “image quality”.
The higher the bit rate assigned to “voice”, the better the “sound quality”.
Also, the sum of the two bit rates is “is called the oval bit rate (total bit rate)”. (This oval bit rate is called “video bit rate”)

▲ If you open the video file properties and open the “Details” tab, you can see “What is the bit rate?”

(However, this Windows function is unreliable, so it is better to use video analysis software like MediaInfo)

soon,

Oval bit rate = video bit rate + audio bit rate
It becomes the calculation formula.

So even if it says “bit rate is high!”, It may mean “video bit rate is high” and “audio bit rate is not high”.

In other words, in such a case, the video will be “Image quality is good, but sound quality is not good …”.

Basically, the file size of “audio” is much smaller than that of “video”, so even if you increase the bitrate of “audio” significantly, the overall size of the file will not change as much.

Therefore, “speech” is often encoded uncompressed (linear PCM).

Relationship to image quality
The higher the “video” bit rate, the more accurate the color information that can be assigned to all pixels.

as a result

High bit rates improve image quality and
If the bit rate is low, the image quality will deteriorate.

▲ High bit rate (12 Mbps, 2.57 MB) ▲ Low bit rate (90 kbps, 20 KB)
* Actually, it is a gif video, so the bitrate is not accurate.

Bit rate difference

Also, in the case of a low bitrate, if you allocate bits evenly to all pixels, you will run out of bits, so in scenes where similar colors are continuous (such as a scene where the blue sky stretches without end), etc. Try to reduce the bits preferably.

As a result, “block noise” ↓ is likely to occur in such scenes.

Block noise
▲ Example of block noise (block noise)

Relationship to sound quality
The audio bit rate is

Sampling rate (Hz) x bit depth (bit) = bit rate (bps)
It can be expressed by the formula.

For example, when recording sound as digital data

How often do you record (= sample rate)
How much data is stored per interval (= bit depth)
Decide and register.

for instance,

Sampling frequency: 44000 Hz
Bit depth: 24 bit
If so, the sound is divided and recorded 44,000 times per second, and the sound is recorded using 24 bits for every 44,000 times.

In other words, if you want to improve the sound quality, you can increase the “sample rate” or “bit depth”.

Increase the sample rate → Soft sound
Increase the bit depth → Increase the expressiveness of the sound, such as finesse and volume
Reference: Meaning and Relationship of Sample Rate, Bit Depth, and Bit Rate

Relationship to codec
I mentioned earlier that “the higher the bit rate, the better the image quality and sound quality”, but the image quality and sound quality are “codecs”. they are closely related to the “.

A “codec” is something like a “compression algorithm” for compressing “video” and “audio”.

Reference: What is video format? Codec difference

for example, “the H.264 video codec” It is a very famous codec that is also used on Youtube and Nico Nico Douga,

(Addendum: Not used now …)

“H.265” which improved the “image quality by file size” from “H.264” There is a codec called “which.

“H.265” is “H.264 at about half the bit rate of”, “H.264 will get the equivalent of image quality and”. (The compression rate is double)

for instance,

Using “2Mbps” video bit rate with “H.264 codec”
Video using “2Mbps” bit rate with “H.265” codec
If there are two videos, the image quality of “H.265” is twice as beautiful even though the bit rate (file size) is the same.

Bit rate, what is it?

Bit rate, what is it?

as a feature of digital audio and video

Bitrate: literally, the information bit rate. It is common to use the bit rate when measuring the effective information transmission rate through the channel, that is, the “payload” transmission rate (in addition to that, the channel can transmit service information, for example, start and stop symbols for asynchronous transmission or control symbols for redundant coding). The baud rate, which takes into account the total bandwidth of the channel, is measured in baud.

Bit rate is the number of units of information required to store (transmit) one second of a stream of data (generally audio and video files). It is generally measured in ‘kbps’, kilobits per second.

The term bit rate is used in two basic meanings
: channel or device characteristic: the maximum number of bits that can be transmitted per unit of time.
– The size of the data stream transmitted in real time (the minimum size of the channel that can pass this stream without delay).
– A special case is the compressed video or audio bit rate.
Bitrate is expressed in bits per second (bit / s, bps), as well as values derived with the prefixes kilo, mega, etc.

The term bit rate (in conjunction with subjective quality criteria) is often used as a characteristic to evaluate the performance of lossy compression algorithms.

Bitrate characterizes both the density of the information package and its quality. For example, out of two MP3 files compressed with different bit rates, a file with a higher bit rate will have higher sound quality (close to the original). At the same time, a file of a different format, with the same bit rate, can offer both better and worse sound quality.

On an audio CD, information is losslessly encoded at a constant 1407 kbps bit rate.

The MP3 format allows you to encode audio information with constant or variable bit rates from 32 to 320 kbps, that is, they provide five times the compression compared to CD.

Bit rate as a characteristic of digital video and audio

In streaming video and audio formats (such as MPEG and MP3) that use lossy compression, the bit rate parameter expresses the degree of compression of the stream and therefore determines the size of the channel for which it is compressed data transmission. Most of the time, the audio and video bit rate is measured in kilobits per second (kilobits per second in English – kbps), less often – in megabits per second (for video only).

There are three compression modes for data transmission:

– with a constant bit rate (constant bit rate in English – CBR)
– with a variable bit rate (variable bit rate in English – VBR)
– with an average bitrate (English Average Bitrate – ABR)

Variable and average bit rate

The codec chooses the required bit rate based on the parameters (the level of the desired quality) and, during the encoded chunk, the bit rate may change. When compressing audio, the desired bit rate is determined based on the psychoacoustic model. ABR is a variation of VBR in which the codec is compressed to a specified average value.

What is bitrate: a clear explanation for beginners

Bit Rate

Once a student was teaching a class and asked me to give him the clearest possible explanation of what bitrate meant.

Today I am going to share with you that explanation that although it does not refer to sound but an image in the background, it is the same and is very easy to understand.

bit rate

Imagine that you put me in front of a beautiful landscape full of rivers and trees, mountains and Valleys with some Villas with Fields full of flowers and animals.

There is a lot of information there if I had to make a detailed description.

Imagine that you ask me to give you a description in 4 words.

It would have to make a very general description that, being very brief, Nova contains details. Maybe I’ll say something like “a beautiful autumn landscape.”

if after that you tell me that now I will have 14 words to describe what I am seeing.
I’ll be able to give more information Although it will really continue to be very summary, but you could already give some details.
“a beautiful autumn landscape with fields and mountains that have houses, flowers and animals”

If they ask me for the following explanation and they already allow me to use 50 words, I will be able to give many more details.
Although of course I will still have to omit a lot of details.

How many words might I need to give a detailed, spoken portrait of what I am looking at?

Well, this example that I just gave of the four words at the beginning then 15 words later have maybe 500 words later is exactly what the bit rate is.

We are talking about what is the amount of information that our audio or video file can transmit per second and obviously The higher the information There will be more details and therefore a higher quality and on the contrary the lower the information the lower the details and therefore lower quality.

That’s why a bit rate of 320 thousand bits per second will have a much higher audio quality than one of 90,000 bits per second.

Because in music, images and video, the quality always depends on the amount of information.

And in the specific case of audio and video, the amount of information is measured by seconds.

This means how much information it can transmit per second, that is, how many bits it can transmit per second, which means How much information and therefore How much detail, which is synonymous with quality.

With this we will understand very easily that as well as the sampling frequency is also very important and we will explain it in another article.
The rate of bits that are transmitted per second is crucial in determining the quality that an audio or video will have.

Of course, it must be understood that the higher the bit rate per second, the larger the size of the audio file will be because the greater the amount of information stored will be, but this will result in higher quality and greater definition.

Because here the definition concept is crucial.
The higher the bit rate the higher the definition and therefore the higher the quality.

The definition would be the detail of our initial explanation, if they let me use 2000 words to describe a landscape, I will be able to give many details and define them with great clarity. And that will mention a lot of quality.

This As-is applies to audio or video files.

Surely with this explanation it has been much clearer what is the rate of bits per second and why it is important.