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Bit rate concept

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Bit rate concept

Bitrate

Concept

Bitrate

Bitrate: literally, the transmission rate of information bits. 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 data stream (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.
Bit rate is expressed in bits per second (bit / s, bps), as well as values derived with the prefixes kilo-, mega-, etc.

The term bit rate (along 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 a 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 a constant or variable bit rate 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 thus 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 (kilobit 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 bit rate (English Average Bit Rate – 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.

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How to Achieve High Quality Videos with Low Bandwidth Part 2

How to Achieve High Quality Videos with Low Bandwidth Part 2

Bitrate

In contrast, a variable bitrate preset a certain level of image quality that is maintained regardless of whether there is movement in the frame or not. The bit rate will change depending on the shooting conditions and the presence of motion.

Bitrate

Dynamic Noise Reduction, as described above, works on the same principle as Variable Bitrate, but with the addition of smart decision-making capabilities based on the presence or absence of motion. This can reduce the bit rate by 50 percent compared to the standard variable bit rate in non-motion scenes.

Priorization
In addition to reducing noise, prioritization can help lower bit rates. By setting priority areas, you adapt the level of compression for different parts of the image. In the image, you can mark several areas, each of which is assigned the parameters of the compression level. A less important area can be configured to use a higher compression rate and therefore a lower bit rate, while important areas can be assigned a lower compression rate to display in more detail.

Take, for example, video surveillance at the entrance of a building. Some parts of the image showing the sky can be considered unimportant for better compression. The area at the entrance of a building can be marked as important and assigned a lower compression ratio to ensure recognition of facial features and other identifying details. Finally, the driveway can be defined as a zone with normal compression.

Reduce costs with dynamic noise cancellation
The combination of noise reduction and image area prioritization produces measurable results. The key advantage of this combination is that you get a significantly lower bit rate without losing image quality. A lower bitrate, in turn, reduces bandwidth and memory usage.

Take, for example, a shopping center with a video surveillance system with 200 surveillance cameras installed throughout the premises inside and outside the facility. Let’s say the mandatory requirement for 1080p HD video surveillance cameras is to record continuously for 12 hours every day, and after the mall closes, they can only record when motion is detected. In this case, to store the video recorded at a rate of 10 frames per second, you will need almost 70 TB, which will allow you to store it for 30 days. The introduction of surveillance cameras that use dynamic noise reduction can save more than 7 TB of required storage capacity. This translates to over $ 10,000 depending on the storage devices used …. Additional savings can also be achieved by adding priorities in certain areas, which will further reduce the bitrate.

Using dynamic noise reduction and priority targeting in small CCTV systems can provide the ability to record video at a higher frame rate for smoother video (when there are moving objects in the video) at the same cost.

Consider, for example, installing a CCTV system in a retail store with 10 CCTV cameras. Using ten indoor 720p HD video cameras, continuously recording for 12 hours every day, and after the store closes, recording when motion is detected, it can store video recorded at a frame rate of 10 frames per second for seven days using the storage device with a capacity of 4 TB. Now let’s look at the same scenario using the dynamic noise reduction method. With Dynamic Noise Reduction, you can stream video at 20 fps and achieve the same storage time using the same 4 TB storage device. You get smoother video movement for the same price.

The ability to reduce bitrate and therefore bandwidth and memory will be even more important as the industry is moving towards the next generation of 4K images. This is characterized by even higher data volumes and therefore higher bandwidth and storage requirements. As a result, a solution that provides high-quality video with the lowest bandwidth and storage requirements will be the most affordable option for customers.

How to Achieve High-Quality Videos with Low Bandwidth

How to Achieve High-Quality Videos with Low Bandwidth

BITRATE

Megapixel surveillance cameras provide their users with more detailed images; however, these capabilities can affect the cost of the entire video surveillance project.

Bitrate

The amount of data that is transported and stored, in this case, increases significantly. Bandwidth requirements and increased capacity required significantly increase the total cost of an IP video surveillance system. The best way to reduce these costs is on the surveillance camera itself, and this can be achieved by reducing the bit rate.

The bit rate can be reduced, in particular, due to noise reduction. Noise is quite a damaging factor that leads to clogging of the encoding process. It leads directly to an increase in the bit rate.

Optimize bitrate to reduce streaming

Classic noise reduction systems are of two types. Spatial noise reduction techniques are applied within the frame to help reduce noise, while temporal noise reduction averages the pixels over multiple frames. These are very effective techniques for still images, but they can cause problems when there is movement. In the event that a temporary noise reduction is applied to a moving image, a ghost image may appear.

By combining spatial and temporal noise reduction with the ability to dynamically adjust them based on lighting levels and the detection of moving objects, we obtain images with low noise, maximum detail and low bit rate. The bit rate can be optimized by adjusting the amount of noise reduction based on the analysis of important moving objects in the surveillance camera’s field of view. When there is no movement, the bit rate is kept to a minimum. If an important object is detected, the bit rate increases, allowing you to capture as much detail as possible. The result is that the bandwidth requirements of the network remain low until something important happens in the frame.

Other ways to reduce the bit rate
For some megapixel surveillance cameras, the bit rate is limited by default. Constant bit rate is often used for this. The constant bit rate is kept at a fixed level. This can result in a constant high bit rate, and setting a low bit rate can result in poor image quality.

Bit rate in DVR. What is it and what does it affect?

Bit rate in DVR. What is it and what does it affect?

Bitrate

In a conversation about digital video recording, the term bit rate will surely ring a bell. This is an important parameter that affects image quality. Including filming on a video recorder.

BITRATE

If you are afraid of foreign words, then the bit rate can be called the recording speed or the compression ratio in another way. Because that’s exactly what happens: the compression of the video stream. How? Let’s take a look.

After the light hits the matrix and the subsequent digitization of the image, a very dense stream of digital video signal is obtained at the output. Also, the higher the video recording resolution and frame rate, the bulkier this stream will be. You cannot write it directly to a memory card; It will fill up very quickly with huge video files and you may just not be able to cope with such a flow of information. This is why the original video stream is compressed to an acceptable bit rate. This parameter is just the output data rate. Basically it reflects the speed at which the video is written to the memory card.

Bit rate can be calculated in bits, kilobits, and megabits per second – (bit / s, bps, b / s), (kbps, kbit / s, kbps) (Mbps, Mbit / s, Mbps). Most of the time, in megabits. The bit rate of the recorded video can be checked on a computer with a video editor or through the file properties menu. By dividing the figure by 8, you can determine it roughly in megabytes per second; it will be more convenient to compare it with the speed of your memory card.

The bit rate indicator is dependent, as you might guess, on the processor and intelligently optimized hardware and software to process the video stream. If all the conditions are met, the video stream will be compressed with high quality and with minimal loss. Otherwise, the video will contain noise, blurry images, artifacts, and other nasty distortions.

The bit rate also affects the size of the file. For example, at a relatively low bit rate (less than 10 megabits per second) more clips can fit on the memory card and cheap low speed cards can be used, but the video quality and details will be low. At a higher bit rate (10-20 begabits per second and more), the image will be of higher quality and more detailed. But the file size will also increase, so you need a memory card of the appropriate size and speed (16GB and above, class 10).

Manufacturers rarely indicate the bitrate on the box, therefore it is almost impossible to find out this indicator before buying. However, sometimes on the packaging you can see promises, for example, “8 hours of video in maximum quality at 32 GB”. And in this case, the bit rate can be roughly calculated. The formula is not complicated:
We took 32 gigabytes and, using the school’s computer skills, we converted them to megabits by multiplying them by eight and by 1024. Then we divided the resulting number by the number of seconds in eight hours.
– (32x8x1024) / (8×3600) – We get the result of 9.1 megabits per second.

Let’s clarify that the result will be conditional. First, because the actual volume of any card is always less than indicated. Second, the promises in the box can be just promises. Therefore, before buying, it is better to carefully study the selected model, having learned the speed of writing in the reviews.
So what bit rate should I be aiming for?

Given the adequate quality of the filling of the recorder (matrix + processor + lens + software), according to our practice, let’s say that this indicator is in the region of 15-45 megabits per second. This bit rate allows you to get a fairly adequate video quality during the day. Again, only during the day, because night photography, as we all know, is still a weak point of many recorders due to insufficient lens aperture and small matrix pixel size.

Note that DATAKAM has currently reached the maximum bit rate for recorders: 45 megabits per second, but only when working with a card with a capacity of 32 gigabytes or more. Some companies, notably Datakam and BlackVUE, are implementing bit rate selection options in settings. We find this option controversial. In our opinion, all drivers are initially interested in the highest quality videos, and it is easier to set the maximum bit rate for the recorder right away and simply choose the right memory card in terms of speed and volume.

And the last thing: they are unlikely to increase the bitrate incessantly on DVRs.

What is the video and audio bit rate?

What is the video and audio bit rate?

Bit Rate

Do you like video production or do you value high quality in movies? You’ve probably come across something like bitrate. It always accompanies the technical characteristics of video recordings and its value determines the quality of the image in the file. When working with converters, you will come across this feature more than once, so it is advisable to fully understand what it is responsible for and how it affects the final product: a video or an audio file.

bitrate

To find out what bit rate is, it is worth understanding how video information transmission works. Any video is a rotating sequence of images. In order not to have a “slideshow feel”, the image change speed must be at least 24 frames / sec. Each box has parameters: width and height. The higher they are, the more pixels are placed in an image, the higher the quality.

Each “point” that makes up a frame has a weight and is equal to 1 byte. Let’s take a Full HD picture and calculate its weight – about two megabytes will be released (1920 x 1080 = 2073 600). So one second of video, containing 24 frames, would weigh 48MB. This is where the concept of bitrate comes in: it is the power to compress a video.

Those. the required file, being encoded, loses weight. But due to strong compression, it may also lose quality. Of course, in reality, not everything is so simple; Much depends on the codec used for encoding. This is the name of the direct compression method. So videos in different formats, but with the same bitrate, can produce images of different quality. The concept of “audio bit rate”, denoting the strength of compression, is also applicable, but for an audio stream.

Bit rate types
Delving into the topic, it is worth noting that the bitrate is not always the same. And now we are not talking about a quantitative indicator, but about a division into types. To work competently with media conversion, read about three types of bitrate: constant, variable, and average, which is a hybrid of the first two.

Constant Bit Rate (CBR)
As the name implies, this type of bit rate does not change during file playback. This compression method allows you to fairly accurately determine the size of the output file and ensure consistent quality throughout your listening or viewing session. But in the entertainment industry, constant bitrate is rarely used due to the impossibility of adjusting it. for dynamic playback, because the files get bigger than they could be.

Variable Bit Rate (VBR)
This type of bit rate is flexible and resistant to change, as a result of which it can be adjusted to the playback object and produce an optimal size / quality indicator. For example, for pictures or musical pieces with a reduced information density, the bit rate will decrease, thus reducing the weight of the object.

Average bit rate
This view is a compromise between the previous ones. The problem with variable bitrate is that changes are automated, and sometimes overcompression can occur. Average bitrate allows the user to set the range in which compression variation will occur. True, the technique of its use is not so simple and is mainly used in professional studios when working on serious projects. An additional advantage of the average bitrate is that it allows you to more accurately calculate the file weight even when the compression force changes.

Explanation of the sample rate, bit depth and bit rate

Explanation of the sample rate, bit depth and bit rate

Bit Depth

This is what happens when you compress audio files
High-resolution streaming and audio promise us particularly good lossless sound when playing digital music. But what exactly does that mean? Sample rate, bit depth, and bit rate are explained.

16-bit 44.1 kHz – CD Quality: This slogan is often used when marketing high-resolution and lossless audio formats and equipment. But what exactly is it about?

israelburrows | Israelsaepblog

The quality of digital audio signals is primarily determined by three things: sample rate, bit depth, and bit rate.

In principle, you have to imagine that a digital audio signal is not a constant flow of information. Rather, music is divided into very, many small “slices” (samples), each of which carries the information for the digital-to-analog converter in a short section.

The more samples a signal has per unit time, the more precisely the original analog signal can be mapped.

The sample rate reveals how tight the samples are: the 44.1 kHz of a CD represents 44,100 samples per second.

Bit depth

Bit depth (resolution) is specified in “bits” and indicates how many different values each sample can assume. With 16 bits (CD quality), this is 2 ^ 16, that is, 65,536. The recording studio usually works with 24 or even 32 bits.

This is where many high-resolution formats come into play that also promise studio quality at 32-bit resolution.

▶ ︎ MP3, FLAC, ALAC, WAV – the most important music formats in comparison

Bit rate

The bit rate (bandwidth) of an audio file in uncompressed formats is initially nothing more than the summary of the sample rate, the bit depth and the number of channels. It is specified in kBit / s and therefore provides an initial characteristic value for evaluating the quality of a file.

Example: A stereo CD stores two tracks at 44.1 kHz with a bit depth of 16 bits. This means that its bit rate is 44.1 kHz x 16 bits x 2 channels = 1411.2 kBit / s

What does “bit rate” mean in a video?

When downloading videos from the Internet or copying videos from disc to your computer, you may have the option of choosing a different bitrate. Even DVDs have specific bit rates. As technology has advanced, video media are able to achieve higher quality, such as high definition DVD, and this is achieved by increasing the video bit rate.

Bitrate

Definition

Bit rate, sometimes referred to as “bit rate”, is the term used to define compression of audio, video, or other multimedia compression in terms of the amount of data, measured in bits, per unit of time in the printed material. Bit rate is the ratio of quality to time. Bit rate is also often measured in kilobits or megabits per second.

Bitrate

Sense

Videos with a higher bit rate will have a larger file size. For example, it will take longer to download or stream from the Internet and upload to a device or computer, and you can burn fewer videos to DVD. However, a higher bit rate usually indicates a higher quality. In this way, your video can be clearer and sharper. When browsing for video or importing it to computer from DVD or camera, choose the highest bit rate for higher quality. However, if space is your main concern, choose the lowest bitrate when downloading or compressing video files.

bit rate factors

Programs will have different bit rates depending on different factors. For example, the output material may have more depth and quality, thus producing a higher bit rate. High definition movies have a higher bit rate than standard definition, for example. Different types of video files have different bit rates and you can also choose different bit rates for the same file. For example, iTunes allows you to compress audio files with a bit rate greater than 128 kilobytes per second to save space on your iPod.

Standard bit rates

Most standard definition DVDs have a maximum bit rate of 9.8 megabits. High definition television has a bit rate range between eight and 15 megabits per second, while the standard for 720p high definition video is approximately 19 megabits per second. At the time of publication, Blu-Ray DVDs have the highest bit rate of all consumer videos with a maximum of 40 megabits per second. This makes the content of Blu-Ray DVDs more than four times that of standard DVDs.

Understanding the bit rate

When you start to make comparisons between video cameras you are faced with a series of aspects to take into account: numbers, characteristics, options … One of the lesser known but no less important issues is the bit rate. Let’s find out what it is, once and for all.

Bit rate

What is the bit rate?

Bit rate is the amount of digital information (bits) that is transferred or recorded in the unit of time.
In the case of video, the bitrate is generally expressed in bits per second, and the amounts being played to date are Mbps (Megabit, that is, millions of bits, per second) or kbps (kilobits, thousands of bits per second).

Bit rate

Because it is important

The bit rate is a parameter to take into account because it affects many aspects of digital production, both technical and more practical (ie economic).
First of all, it affects the quality of the video and the size of the single file: obviously, the more data is transmitted in the unit of time, the higher the quality of the recording. And at the same time, it will increase the size of the recorded file.
However, this should not lead us to think that a very high bit rate is always necessary: in fact, we must bear in mind that as the bit rate increases, the difference becomes more and more marginal.
Basically, bit rate variations made from already high values to reach higher values are less visible than variations made from low values.

Then there is the question of file accessibility on the network: if the bit rate is very high, it will take a long time to download a video and watch it (for example, YouTube recommends not very high bit rates).

Finally, the bit rate also influences our portfolio: if we want to record at very high bit rates, we must first have a higher performance equipment, and then we will have to have more capable and higher performance media. Hence, larger SD, with high write speeds and consequently higher costs.

This is why you need to know what bitrate is, especially if you are serious about creating videos.

Bitrate, framerate and resolution

To get an idea of the concept of framerate you can read this article that talks about 24 fps and the cinema effect. Instead, resolution is simply the number of pixels the camera uses to “describe” the scene – more pixels means more resolution and therefore more detail (up to a certain limit).

Why are we talking about these other two concepts? Because the bit rate is a bottleneck that can make you lose part of the information we want to record.

A little math

Let’s imagine that we have our machine and we set it to 4K and choose a frame rate of 60 frames per second.
Now let’s take the same machine and set it up in HD choosing a frame rate of 30 frames per second.

How will the bit rate change?

Since the bit rate is bit / second, let’s try to calculate the bits to transfer in each case.

-In the first case we will have 4096 × 2160 pixels, all multiplied by the 60 times in one second that the frame is recorded: a total of 530841600 pixels.
In the second case, however, 1920 × 1080 pixels multiplied by 30 frames: a total of 62,208,000 pixels.

That is why the bit rate can be a bottleneck: each pixel is represented by a certain number of bits, and if we record with resolution and framerate parameters that exceed the bit rate possible with a certain machine, this will have to apply compression to the file. And we know that the more compressed a file is, the lower its quality.

What is the bit rate and how does it influence the quality of the videos?

Amid the pandemic we are facing and authorities increasingly asking people to stay home, the use of the Internet, especially broadcast services, is skyrocketing. Amazon Prime Video, Netflix, YouTube, Twitch and others have already announced measures to try to ensure everyone accesses their videos without gagging, but there are differences between the measures on some platforms.

YouTube reduces standard video quality to SD worldwide

Netflix, for example, opted for a reduction in the data rate or bit rate without lowering the resolution of the video itself. YouTube is already one of the platforms that now forces you to load at a lower resolution while maintaining the data rate, that is, the final quality, and allows you to increase the image size manually by the user.

bitrate

Oops wait! So does reducing resolution not reduce the quality and quantity of data to transfer? Not quite. Resolution is not the only thing that defines the quality of a video image, or even a JPG image, audio and the like, there are a number of factors. Among them, in addition to the image size, the bit rate that will be transferred from a server to a device, for example.

Data rate versus bandwidth

Reducing the amount of data sent to each user can help guarantee the service for everyone (Photo: Pixabay)
To understand metering on Netflix, you first need to understand the difference between the data rate of a media file and the bandwidth of the connection. Both can be called bitrate and throughput, and whether those terms are correct or not matters little. What matters is that it confuses, so it is necessary to clarify it.

The data rate of a media file refers to the maximum size of a second of the video. A video, as you may already know, is divided into frames, the most common speed is 30 fps (30 frames per second). Each table has its own set of information, and the total of 30 (or 24, 60, 120, and the like) forms the bitrate.

The bandwidth of the connection is the speed of your internet. Brazilian 4G, for example, has an average of 20 Mbps. Some fixed broadband operators offer packages of 100 Mbps, 200 Mbps or even more. This rate is the maximum amount of data that your Internet can receive from a central server.

Data volume

YouTube chose to lower the standard resolution without decreasing the volume of data (Photo: Pixabay)
The bit rate of a media file, therefore, is the amount of data it has each second. Netflix reduced this rate to decrease the amount of information that its servers need to send to each user connected to the platform. This reduces the quality of the image because it is less data, which can slightly reduce sharpness and cause noise, which some call “pixelization”, especially in very dark areas of the frame.

The resolution is not the lowest: it is that this image has less information. When loaded onto a large screen such as a TV, details are missing to display. On smaller screens, you will hardly notice the difference.

Facebook and Instagram will reduce the quality of video in Brazil
Globoplay will reduce video quality to meet demand
In short, Netflix’s decision ensures resolution, keeping sharpness a little closer than the user is used to, but reducing the amount of data transferred, resulting in images with a lower level of detail and sometimes , even more noise, even.

By sending less information to each user, Netflix, as well as Facebook, Globoplay and other services with similar measures, the platform avoids what we call server bottlenecks. This could cause suffocation and connection failures. YouTube’s measure also alleviates traffic because not everyone will manually increase the resolution, which in itself already reduces the amount of information to be transferred.

What is a video bit rate? What is mp3

The bit rate is of two types:

internal: the number of bits transmitted per second;

external: data rate and its value for real-time transmission (to watch a movie or listen to music).

Let me remind you that high bitrate usually means better quality, however this may depend on the source file.

How to find out the bit rate of a specific file?

It can usually be found right inside

And what is the difference, let’s see?

There is said to be little difference. 🙂 In my opinion)) (hearing), it is necessary to listen to music not through the speakers for 100 rubles, and certainly not through a portable speaker. C and everything fits immediately: it does not sound, but cacophony, if the bit rate is less than 120 kbps.

Bitrate

Different bit rates for people who work with sound. Well, to listen at home, any bitrate, even the lowest bitrate, will. Here it is, as the saying goes, an amateur.

Incidentally, one of the “representatives” of music with a high bit rate is the .flac format. . , the bit rate weighs less than 800-1000 kbps, however it takes up more space, such a song can weigh 30mb, and the album less than 400.

I hope this explanation of “What is the bit rate in music” has helped me a little? Please leave the comments below so I can reply to you.
Don’t be afraid of me and add

With the concept of “bit rate” we are faced with the mention of files in audio and video format. To understand the essence of this term, you must master file compression and encoding. German scientists have established the general principle of compressing files with minimal loss. Using the MP3 encoding example, the source audio file is cut into chunks lasting 50 milliseconds, each of which is analyzed separately. In the analysis, the fragment is broken down into harmonics according to the Fourier method, of which, according to the theory of sound perception, the harmonics that the person perceives worse than the rest are expelled from the human ear. These are quieter harmonics in the context of the stronger ones. As a result, sounds masked by hearing inertia are ejected (for example, if a very short beep sounds at once, with a delay of a fraction of a second, some other short-term signal is heard, then it will not be heard. ) The remaining harmonic information after filtering is recorded in an MP3 file, which results in a much smaller size than the original WAV. The WAV file stores complete information about the original sound, digitized and quantized at a frequency of 44 kHz. This information is stored on normal audio CDs. During playback, a reverse transformation is performed, in which the remaining harmonics are converted back into a sound wave. Some information about the original signal has disappeared, therefore the sound is not the same as the original. But insignificant sounds have been thrown, so the human ear cannot distinguish the signal from the original, which it was before packaging in MP3.

Bit rate is the amount of information per unit of time. Its essence: how much information about each second of the registry can we spend. Of course, the smaller it is, the smaller the files are with the same duration over time, so they have to throw more “extra” harmonics. Bit rates have units of measure: kilobits per second (Kbps) and megabits per second (Mbps). The MP3 audio compression algorithm is often used with 128 kbps compression. They are of two types: fixed and variable. So with video compression, if a constant bit rate is applied, a fixed amount of data is used to encode a second of a movie. In the case of variable bitrate, the codec sets its own bitrate value based on the scene in the movie. For example, when encoding in MPEG, in practice, the compression gain is obtained by saving only the difference between adjacent frames. With a slow scene change, the difference between the frames is small, and therefore it is possible to reduce the bit rate required to reproduce these scenes.