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Bitrate and its calculation Bit rate (bit rate) Part 3

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Bitrate and its calculation Bit rate (bit rate) Part 3

bit rate

coding.

bit rate

Codecs and Media Containers

Since 2014, the most common high definition video format is HD (Full HD), with a screen resolution of 1920 x 1080 pixels and a screen aspect ratio of 16 x 9. (This format is compatible with most modern LCD and plasma televisions, but not all are capable of providing a high quality picture.
The fact is that most of these televisions have a lower screen resolution than is necessary for viewing in Full HD, for example 1280×720. The HD format has varieties: 1080i and 1080p. As with other formats, the letters i and p represent progressively scanned or interlaced images.

But, unlike the usual PAL and NTSC formats, here with interlaced scanning the frame rate is 60 and with progressive scanning 50 frames per second. This is a standard, you can stick to it, but you can work around it too. The fact is that today a full HD format can only be played on a computer, there are no special devices (players) to watch it (HD DVD (gradually dying) and Blu-Ray disc players do not provide Full HD quality, but more on that later), therefore full compliance with the rules is no longer as important. The next most common high definition video quality and format is HDV, with a screen resolution of 1440 x 1080, but also with a 16×9 aspect ratio. This ratio is achieved by “stretching the pixels” horizontally, from 1440 to 1920. Therefore, for a Full HDV display, a FullHD television with a screen resolution of 1920×1080 is also required. Of course, the video quality in HDV format is lower than HD, but still, HDV format is quite common among users. The reason is that the HDV format was invented before HD, and even before the latter came out, a lot of video equipment was developed and released that only supports 1440×1080. High definition movies, generally recorded on HD DVD and Blu-Ray discs, also have an HDV resolution of 1440 x 1080. Even before the advent of HDV and HD, the 720p “high definition” format appeared. The resolution is 1280×720, the aspect ratio is 16×9. It is essentially a transitional format, from standard PAL to HDV and HD. The world’s first “high definition” hobby camcorder produced by JVC recorded at 720p. Even earlier, the PAL television format appeared in 720×576 resolution with 50 Hz interlaced scan. Now, this format is used in digital and satellite television (not HD). Now (2014-2017) I use mp4 format: mp4 – Full HD – 1920 x 1280, 16×9 variable bit rate 10 – 15 mbps for home viewing on 64 inch Full HD TV, this is enough. mp4 – HD – 1280 x 720, 16×9, variable bit rate 4-6 mbps. – if you need to save disk space, or if quality doesn’t really matter (or if you need to speed up rendering).
Источник: https://vseprost.ru/vybor-bitrejta-dlya-zapisi-multimedia.html

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Bitrate and its calculation Bit rate (bit rate) Part 2

Bitrate and its calculation Bit rate (bit rate) Part 2

bit rate

Let’s go back to the DVD story for a moment.

bit rate

When the first analog-to-digital converters appeared in capture card form, it was claimed that 60 minutes of video could be put on a DVD-R with no loss of quality. In the claimed presentation data of the DVD format, the maximum bit rate of the multiplexed stream is 9.8 Mbit / s. When DVD recorders appeared that were capable of digitizing an analog signal in high quality, it was said that the recorder could fit up to 125 minutes on a disc without losing quality and up to 90 minutes if you wanted to save sound in PCM format.

We test, we verify, we write from both disk and videotapes; there is no visual difference even during pauses and in frame by frame mode (if the recorder is good). The bit rate that the recorders give to the output of the digitized image is 9000 Kbps and sometimes a little more. Why is the math not the same as the DVD burner result?

Probably because we do the calculation for a constant bit rate, and the recorders can already digitize video with a variable bit rate and have appropriate compression algorithms. By setting the upper limit of the bit rate at 9000 Kbps, you can achieve a good picture in video segments with dynamic actions, while in other parts of the same video the value of the bit rate can reach 2000 Kbps. noticed that when you record a video or a photo with a digital camera, the files have different sizes? Once the initial parameter is set, the codec itself chooses the value of the bit rate. Optimal bit rate for DVD video Considering the fact that up to 120 minutes of video can be recorded on DVD-R without quality loss, we ask ourselves: how to do this? Let’s consider 2 ways: 1. If you are using a DVD burner, set it to “lossless quality” mode and set to record. If your video is 60 minutes long, the recorder will not stretch it by 4. 36GB and it will only take up half the free space. 2. If you use a capture card or TV tuner, first capture as described here and then compress the resulting file with a quality program with modern codecs and multiple passes (at least the same Freemake Video Converter) at the speed of dvd5 for 120 minutes (don’t forget the menu). Consider an option when your video is short and you are not going to burn it to DVD-ROM or if you want to burn multiple MPEG-2 files to disc at once without losing quality. Below is a table calculated mathematically on the basis that you can fit 120 minutes of video on 4464MB of disk space (no menus). There are a few things to keep in mind: The table is written for MPEG-2 files. The table is not written for previously compressed videos. These values do not include a menu. Using different programs, you can get different results. The values in the table may vary depending on the content of the video. If the program has a bit rate option then you need to set “VBR” (variable). The values in the table are based on “lossless compression”. In this article, “lossless compression” refers to the viewing experience. In fact, in the analytical version, the word “compression” already denotes a loss of quality.
Источник: https://vseprost.ru/vybor-bitrejta-dlya-zapisi-multimedia.html

Bitrate and its calculation Bit rate (bit rate)

Bitrate and its calculation Bit rate (bit rate)

bit rate

Flow rate data per unit of time.

bit rate

Information flow is normally measured in bits and transit time in seconds (bit / s, bps). There are other quantities derived with the prefixes kilo- and mega- (kbit / s, kbit / s, kbps, Mbit / s, Mbps, Mbps). Bit rate is one of the main parameters of a video. Its value affects the size and quality of the video file. The bit rate is directly proportional to the quality and size of the file. The higher the bit rate, the better its quality and the larger the file size. Two types of speed must be distinguished: maximum bit rate: the maximum number of bits that can pass per unit of time, and bit rate: the bandwidth of the channel without delay.

Data stream compression modes

Constant Bit Rate Constant Bit Rate (CBR) is the encoding of the data stream, specified by the user and has a constant value throughout the length of the file. This mode improves compatibility and the ability to calculate more accurately, but can increase the size of the output file. Do not use this mode for dynamic scenes (sports programs, action movies, etc.) and when objects are moving in different directions. Variable Bit Rate (VBR) Variable Bit Rate is a mode in which the codec determines the amount of information stream transmitted based on the complexity of a given file segment. This mode produces the best quality in an optimal size and prevents flickering. The disadvantages of this method include only the unpredictability of the output file size and the possibility of incompatibility. Variable bit rate is actively used for burning Blu-Ray and DVD discs, where there is no limitation on the size of the file as such. Average Bit Rate (ABR) Average Bit Rate is a combination of variable and constant bit rates set by the user. Unlike variable bitrate, the data stream varies within strict limits and does not reach the minimum and maximum values. This allows you to predict the output file size much more accurately than VBR and improve video quality in fast-moving video scenes. The method was applied in the network. This mode is sometimes used to compress audio.

Bitrate calculation

Having mastered what the bit rate is and having disassembled the compression modes of the flow of information, we can proceed to the independent calculation of the bit rate. Let’s establish the conditions of the problem: video: home video 120 minutes long sound: present; menu: necessary; DVD-R Media (DVD + R) 4.36 GB; Output format: DVD (MPEG-2) DVD-R size: 4.36GB = 4464MB. Size is critical, so we will be calculating from 4300MB for several reasons: 1. Bitrate cannot be accurately calculated and the file may be larger than planned. All full disk space sometimes leads to improper disk startup. 3. Many programs are recoding based on this value. We subtract another 300MB for the menu and the audio track (if your sound is not in PCM format, whose bit rate is much higher, and if you don’t plan to create multiple audio tracks) and we get 4000MB. 4000: (120 * 60) = 0.556 Mbps = 0.556 * 8 = 4.444 Mbps = 4.444 * 1024 = 4551 Kbps. For a high-quality DVD-Rip, this value is ideal, but for MPEG-2 it is barely supportable. The fact is, different video formats need different bitrate values for an acceptable picture. You can try to play this video and if there are dynamic moments, you will see artifacts in the shape of squares in the video. It follows from this that you need to reduce the length of the file to about 60 minutes or look for other compression methods.

What is video bitrate, frame rate, and aspect ratio?

What is video bitrate, frame rate, and aspect ratio?

What is a video file?
Video, like cinema itself, is a rapid alternation of images. How fast is it? For a human, there should be 24 images in one second. In this case, images that change rapidly become moving. Film is based on this and now video. Also, each image has several properties. Which? They are wide and tall. Also, for video, these values are measured in points. So many points of width and so many points of height.

What does the video consist of

If we zoom in on any frame in our video, then we can see the individual squares that make up our image. Each of these squares was called “Pixel”, which comes from the English “Picture element”, that is, a picture element.

Pixels on screen

So when we look at the file properties, or the project properties, we see the video formats, which indicate how much the frame is and how wide it is.

video aspect ratio

In the image we can see that the width of the frame is 1920 pixels, and its height is 1080. It is clear that the more pixels in our frames, the more details can be accommodated. And consequently, the better the image will be. At the same time, do not forget that the frame rate must be at least 24 frames per second.

Older video formats, such as the PAL standard, were 720×576 pixels. Modern HD or Full HD, already 1920×1080. Well the latest 4K format is already 4096×2304 pixels. That is, the further, the better quality is achieved.

See Also: Video Codecs, Video Formats – What Does All This Mean?
Video aspect ratio.
This is also a parameter that for many is almost a thing of the past. The fact is, there used to be a TV format that had a 4/3 aspect ratio, and a widescreen format, mainly for watching movies, that had a 16/9 aspect ratio.

Monitor with 4×3 aspect ratio

Now the television format is a thing of the past (almost) and only the wide format remains

Monitor with a 16 x 9 aspect ratio
What is the video bit rate?
Like I said, each frame is made up of a large number of pixels. If we try to put this amount on our hard drive, it will take up too much space. Strictly speaking, the arithmetic here is simple. Let’s count.

One frame – 1920×1080 = 2,073,600, that is, two megabytes (actually, this is not entirely true, but I’ll simplify it a bit)

That is, we now know that a painting we have weighs 2 mb. It seems a bit, but let’s keep counting.

One second. A second must have at least 24 frames. What do we get? 24×2 = 48 mb.

One minute. 48×60 = 2880 mb. I mean, think about it. In one minute, almost 3 gig! Well, how long will an hour take then?

One hour 2880×60 = 172800 mb. In other words, one hour of movie will take up 172 gigabytes of memory.

Well, since such a thing will not work, smart people decided: we must squeeze. We need to compress the video so that we can put everything on a computer, on a phone. What can be seen on the Internet, etc. And that is why there are various video formats. Since each format has its own rules for video compression.

See also: Do you know what a chroma key is? Learn the secrets of working with chroma key in 5 minutes
But here we come to the concept of bitrate.

Bitrate: read / write speed. You are recording a video. The video camera matrix takes measurements of light, that is, it measures pixels. Transfer them to a USB flash drive or SSD. The speed of this transmission is the bit rate.

Next, we watch the video. At this time, the data is read from memory and transferred to the monitor / screen. Again, we are faced with a certain data rate.

But in video, the role of the bitrate value is somewhat different. Video Bit Rate: The video compression rate. When recording video from the matrix, the signal is immediately encoded and compressed. The more the signal is compressed, the less space it occupies, but at the same time, and the lower the quality.

What is a video codec?
Now, let’s move on to the next concept: video codec. When I said that if you lower the bitrate, the video quality will be lower.

What is the bit rate?

What is the bit rate?

The bit rate, or as they also say the width of the stream, is the amount of data transmitted or processed in 1 second. The concept mainly applies to multimedia content, for example, video bit rate is nothing more than the amount of video information that is displayed on the screen in one second. To measure the bit rate, the designation “Kbit / s (kbps)” is used, that is, kilobits per second, less frequently Mbit / s, and so on. The more information that is transmitted during a specific period of time, the higher the quality of the image.

When people say “low bit rate video” they are generally referring to low quality video. Blur, opacity, and pixelation are characteristic features of such video, while high-bit-rate video has a detailed image with a rich color gamut. Like video, audio also comes with low and high bit rates. Music with a low bit rate loses in the frequency range, words and chords become less distinguishable, and itself takes on an unnatural sound, as if it were an electronic sound.

Bit rate types

It is not enough to understand what the video or audio bit rate is. To successfully work on programs for editing and converting multimedia content, you need to know what types of bit rates exist. These are constant, variable, and average, and each of them can be used in a specific situation.

Constant bit rate

Constant refers to a bit rate that does not change throughout the file, providing an accurate estimate of the size of the output material. On the other hand, it is not very suitable for multimedia with dynamically variable audio and video streams, as it does not provide an optimal balance of size and quality. Constant bit rate is mainly used at home level, as well as when processing files with relatively constant picture and sound characteristics.

Variable bit rate

In files with variable bitrate, the latter is changed by the codec for each frame according to its characteristics. For example, in frames that are not very informative and easy to encode, the video bit rate is lowered, which saves space, and this saving can differ significantly. Variable bit rate technology is often used to achieve the best quality / size ratio. The downside of this method is the unpredictability of the final size of the media file.

Average bit rate

A more flexible option is the averaged bitrate, which is a hybrid of the first and second types. Unlike Variable Bitrate, by choosing Average Bitrate the codec can only work within the user defined range. Professionals use this method when creating large projects, allowing you to achieve high-quality encoding with a relatively small file size. The precision of calculating the size is much higher.

How to find out the bitrate of the file

Novice users are often interested in how to find out the video bit rate and if special programs are needed for this. With few exceptions, it is not necessary to use third-party tools for these purposes, since the bit rate of the file can be obtained by the operating system itself. Right-click on the video file and select “Properties” from the menu. Then switch to the “Details” tab in the window that opens and look for the item “Data transfer rate”. This will be the bitrate of the video. In the case of audio files, the item will be named “Bitrate”. If the required information is missing from the properties, for example in the case of MKV files, use the MediaInfo utility.

What bit rate value to set

But much more relevant is the question of what bit rate should be set for a video when creating or converting it. It will not be possible to answer it unequivocally, it all depends on the situation and the purpose of the content. If you focus on average values, you should configure 2.5-5 Mbit / s for video and approximately 192 kbit / s for audio. When choosing, you should also consider the video format. Therefore, for 1920 x 1080 SDR video, the bit rate is better to set 8 and 12 mbps (60 frames / s), and for HDR video with the same resolution – 10 and 15 mbps, respectively.

What is the bit rate?

Bit rate measures the speed at which information can be transmitted between two locations. The standard unit for this speed is “bits per second”, but a kilo or mega value is often prepended to indicate the high speeds of modern digital technology. Communication technology measures speed as a function of bit rate, especially on the Internet. The transfer rate indicates how fast the data can be downloaded. This measure is also widely used to describe audio and video. higher rates mean higher quality.

In its simplest form, bit rate describes how many bits per second are transmitted between two different locations. The higher the rate, the faster information can be exchanged between them. For this reason, the bit rate can be particularly important for communication technologies such as broadband, as it defines how quickly a user can download or upload information.

The standard unit for bit rate is bits per second (bps). However, this measurement is often too small to be practical in modern communication technology, as millions of bits can be transmitted per second. To solve this problem, the device is usually prefixed by a different letter indicating its size. For example, kbit / s means kilobits per second or 1000 bits per second. Megabits per second are written as Mbit / s and represent millions of bits per second.

Bit rate is an important measure for a large number of different areas of computing. Broadband, for example, is often specified as a certain number of Mbit / s, with speeds of around 2 Mbit / s being common. Fiber broadband, which is much faster, can deliver speeds of up to 5 Mbps. This measure also describes the speed of mobile connections such as 3G and Bluetooth.

Audio and video quality are commonly reported in terms of bit rate, with higher rates indicating a higher quality picture or sound. In multimedia, this metric is a quick way to show how much information is stored in each second of recording, so higher rates lead to increased quality. The bit rate can depend on a variety of factors, including whether the information has been compressed.

The standard bit rate for audio is between 100 and 160 kbit / s, while higher quality recordings can reach up to 320 kbit / s. Video speeds can be significantly higher for Blu-ray discs with speeds up to 40 Mbps. Standard DVDs are only about 9 Mbit / s, so there is a difference in quality.