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Video encoding, how it works (part 2)

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Video encoding, how it works (part 2)

So far, we’ve only talked about image compression. But a full video also involves an audio component. CD-quality sound is believed to need to be digitized at 44.1 kHz at 16 bits per channel, which is equivalent to 706 Kbps per channel (1.4 Mbps for stereo). The quality of the DAT signal determines the sampling rate of 48 KHz (frequency band 4-24000 Hz) and increases the stream to 768 Kbps per channel.

The information compression approach is the same: discarding the part that is not very important for the human ear to perceive. The MPEG standard allows 3 layers of audio compression. Layer 1 uses the simplest algorithm with minimal compression, assuming 192 Kbps per channel. The Layer 2 algorithm is more complex, but the compression rate is higher, only 128 Kbps per channel. A powerful CD-quality digital audio compression algorithm (11 times lossless distinguishable by the human ear) Layer 3 provides the highest possible sound quality with severe transmission restrictions – no more than 64 Kbps per channel. It is primarily intended for the Internet. Its importance is so great that it has received a special abbreviation MP3, which stands for MPEG Layer 3. There are many Internet sites that contain hundreds of thousands of MP3 files of popular music. With the help of special playback programs (Real Audio), MP3 music can be listened to in real time over the Internet, copied indefinitely (note that a typical song is 2-8MB), and illegally distributed. There are already portable MP3 players priced around $ 200 (like the Diamond Rio). The music industry, with tangible losses, began an active fight against MP3 sites (the Recording Industry Association of America found and closed most of them). But the gin is out, you can’t close everyone. Adaptec predicts that billions of songs will be downloaded from the Internet in the coming years and announces MP3 support in the next version of EasyCD Creator. However, in digital editing tasks, audio signal compression is not used, therefore, in allowable stream calculations, it is necessary to allocate up to 1.5 Mbps to the audio component.

MPEG2 for non-linear editing tasks

The term non-linear editing does not correspond to the essence of the process, but only reflects one of its characteristics. In fact, we are talking about video editing, done in digital format on computers. In this case, the original video fragments are subject to mandatory digitization and recording on the hard disk in the form of appropriate files. Unlike tape drives, accessing any of these fragmented files does not require tedious rewinding (and this process is linear), meaning all video frames are available in random order. This important property gave rise to the name of digital editing as non-linear, although, obviously, the possibilities of digital processing are much broader and richer.

Remember that according to the ITU-R BT.601 recommendation, a television frame is a 720×576 matrix. Taking into account the television frame rate of 25 Hz, we conclude that one second of digital video in 4: 2: 2 representation requires 25x2x720x576 = 20,736,000 bytes, that is, the data stream is 21 MBps. Recording these streams is technically feasible, but difficult, expensive, and inefficient in terms of post-processing. The real possibilities of practice require a significant reduction in flows. Many algorithms are known to perform lossless compression, but even the most effective ones do not provide more than 2x compression on typical images.

Until recently, M-JPEG reigned supreme in the world of non-linear video editing systems. The different solutions differed in the degree of compression, which corresponded to different levels of quality of the resulting video. Quite conditionally, 4 levels can be distinguished here: Standard Video (VHS, C-VHS, Video8), Super-Video (SVHS, C-SVHS, Hi8), Digital Video (Betacam SP, DV / DVCAM / DVCPRO, mini -DV, Digital8) and Studio Video (Digital-S, DVCPRO50). For simplicity, we will refer to them as Video, S-Video, DV, and Studio-TV in what follows. Quantitatively, they are generally characterized by horizontal resolution (the number of distinguishable elements in a line: television lines). Video is considered to provide a resolution of up to 280 lines and corresponds to an MJPEG stream of approximately 2 MBps.

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Video encoding, how it works (part 1)

Video encoding, how it works (part 1)

The effective compression of video information is based on two main ideas: the suppression of small details of the spatial distribution of individual frames that are insignificant to visual perception, and the elimination of temporal redundancy in the sequence of these frames. Consequently, we speak of spatial and temporal compression.

The first one uses the experimentally established low sensitivity of human perception to distortions of small image details. The eye notices a non-uniform background more quickly than the curvature of a thin edge or a change in brightness and color of a small area. Two equivalent representations of the image are known from mathematics: the familiar spatial distribution of brightness and color and the so-called frequency distribution associated with the spatial Discrete Cosine Transform (DCT). In theory, they are equivalent and reversible, but they store information about the image structure in completely different ways: the transmission of smooth background changes is provided by low-frequency (center) values of the frequency distribution, and the high-frequency coefficients. They are often responsible for the fine details of spatial distribution. This allows the following compression algorithm to be used. The frame is divided into 16×16 blocks (720×576 corresponds to 45×36 blocks), each of which is converted to DCT in the frequency domain. Then the corresponding frequency coefficients are quantized (rounding of values with a given interval). If the DCT itself does not lead to data loss, the quantization of the coefficients obviously causes a thickening of the image. The quantization operation is performed with a variable interval: low-frequency information is transmitted more precisely, while many high-frequency coefficients take zero values. This provides significant compression of the data stream, but leads to a decrease in effective resolution and the possible appearance of minor spurious details (particularly at block boundaries). Obviously

For attentive readers, we repeat that this algorithm came from digital photography, where, under the name JPEG, it was developed to efficiently compress individual frames (JPEG is an abbreviation of the name of the Joint Photographic Experts Group, which endorsed it). It was then successfully applied to frame video sequences (each processed completely independently) and renamed MJPEG (Motion-JPEG). It should also be noted that the DV encoding of the DV / DVCAM / DVCPRO digital standards is essentially based on the same algorithm, but uses a more flexible scheme with adaptive selection of quantization tables. The compression ratio for different blocks, unlike MJPEG, varies with the image: for non-informational blocks (for example, at the edges of the image) it increases, and for blocks with a large number of small details, it decreases relative to the middle level of the image. As a result, with the same quality, the data volume is reduced by approximately 15% (or vice versa, with the same flow, the quality of the output signal is higher).

Temporal MPEG compression uses a high redundancy of information in images separated by small intervals. In fact, between adjacent images, usually only a small part of the scene changes; for example, there is a smooth movement of a small object on the background of a fixed background. In this case, the complete information about the scene should be saved only selectively, for reference images. For the rest, it is enough to transmit only difference information: about the position of the object, the direction and magnitude of its displacement, about new background elements (which open behind the object as it moves). In addition, these differences can form not only in comparison with the previous images, but also with the later ones (since it is in them, as the object moves, the part of the background that was previously hidden behind the object is revealed). Note that mathematically the most difficult element is the search for displaced blocks, but little change in structure, (16×16) and the determination of the corresponding vectors of their displacement. However, this element is the most essential as it can significantly reduce the amount of information required. It is the efficiency of the real-time execution of this “smart” element that distinguishes various MPEG encoders.

MPEG-1 Audio Layer II

MPEG-1 Audio Layer II

MP3 (MPEG-1 Audio Layer III

MPEG-1 Audio Layer II or MPEG-2 Audio Layer II (MP2, sometimes incorrectly called Musicam or MUSICAM), is a lossy audio compression format defined by ISO / IEC 11172-3 in conjunction with MPEG-1 Audio Layer I and MPEG Audio Layer -1 III (MP3). While MP3 is much more popular for PC and Internet applications, MP2 is still the dominant standard for streaming audio.

MP3

Development history from MP2 to MP3

The MPEG-1 Audio Layer 2 encoding was derived from MUSICAM (masking pattern adapted by Universal Subgroup Integrated Coding And Multiplexing), an audio codec developed by the Center commun d’études de télévision et télécommunications (CCETT), Philips and Institut für Rundfunktechnik (IRTfunktechnik) in 1989 as part of the EURECA 147 pan-European intergovernmental research initiative for the development of an audio and data transmission system to fixed, portable or mobile receivers (established in 1987).

MPEG audio

In the late 1980s, ISO’s Moving Picture Experts Group (MPEG) began an effort to standardize digital video and audio encoding, which is expected to have a wide range of applications in digital radio and television broadcasting ( later TOUCH, DMB, DVB) and use on CD-ROM (later Video CD). The MUSICAM audio encoding was one of 14 proposals for the MPEG-1 audio standard that were shipped to ISO in 1989.

The MPEG-1 audio standard was based on the existing MUSICAM and ASPEC audio formats.

The MPEG-1 audio standard included three audio “layers” (encoding techniques) now known as Layer I (MP1), Layer II (MP2), and Layer III (MP3).

All algorithms for MPEG-1 Audio Layer I, II, and III were approved as draft in 1991 by the ISO 11172 committee and completed in 1992 as part of MPEG-1, the first set of MPEG standards that led to the international ISO standard. / IEC 11172-3 (also known as Audio MPEG-1 or Part 3, MPEG-1) published in 1993. Additional work on MPEG audio was completed in 1994 as part of the second set of MPEG standards, MPEG-2, more formally known as International Standard ISO / IEC 13818-3 (also known as MPEG-2 Part 3 or MPEG-2 Audio backward compatible or MPEG-2 BC Audio), originally published in 1995. MPEG-2 Part 3 (ISO / IEC 13818 -3) defined additional bit rates and sample rates for MPEG-1 Audio Layer I, II and III. The new sample rates are exactly half of those originally specified for MPEG-1 Audio. MPEG-2 Part 3 also expanded MPEG-1 audio, allowing audio programs with more than two channels to be encoded in 5.1 multichannel.

Component Layer III (MP3) uses a lossy compression algorithm that has been designed to dramatically reduce the amount of data required to present an audio recording and be like a decent reproduction of the original uncompressed audio for most listeners.

What are CBR and VBR?

What are CBR and VBR?

CBR VBR

As you know, the result of encoding a signal using an algorithm such as MPEG-1 Layer III (MP3) (and many other algorithms) is a bit stream with a frame (block) structure. This is due to the fact that the source stream is not encoded in its entirety, but in parts. That is, in fact, the original stream is divided into blocks of some fixed length, then each block (frame) is encoded individually, and the result (encoded information block) is sent to the resulting stream (either a file or a stream of data).

CBR vs VBR

CBR (constant bit rate) is a way of encoding the original audio stream, in which all its blocks (frames) are encoded with the same parameters (with the same bit rate). In other words, the bitrate over the entire length (all frames) of the resulting stream is constant.

VBR (variable bit rate) is a method of encoding the original audio stream, in which each separate block (frame) is encoded with its own bit rate. The choice of the optimal bit rate to encode a given frame is made by the encoder itself by analyzing the “signal complexity” in each individual frame.

What are the differences between CBR, VBR and ABR for Lame Encoder?

Before starting the conversation, let’s clarify two details:

1. MP3 encoding happens block by block: the encoded file is divided into frames (frames) with the same interval, each frame is encoded and written to the output stream; therefore, the output stream also has a frame structure.

2. Frames cannot be encoded at any bit rate, but only at one of the standard MPEG1 Layer III bit rates listed in the table: 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320. The standard does not provide encoding at intermediate bit rates (“free format”).

Introduction

People using VBR in Lame often argue this with the phrase, “I want to get constant quality, not constant bitrate.” In fact, in music there are simple passages, for which 128 Kbps is sufficient (for example, pauses between songs), and there are also complex passages, in which a person with good hearing, a good audio card and other audio equipment. audio will hear compression defects even at 320 Kbps / sec. In fact, such an argument is not entirely valid.

CBR

Even in CBR mode, the mp3 encoder can reallocate bits over time, emphasizing more or fewer bits during complex or simple passages, thus improving the overall sound quality. This redistribution of bits is carried out at the expense of the so-called bit deposit: during the encoding of simple passages, the encoder spends not the entire user-specified bit rate on them, but only about 90%, about 10% is saved in the repository to encode complex locations (initially repository is empty). When encoding complex passages, the encoder will use 100% of the specified bit rate and add additional bits from the bucket (if any, that is, if the bucket is not empty). Unfortunately, according to the standard, the size of the tank is limited. This means that if a single signal lasts long enough, the tank builds its volume up to certain maximum allowed limits and then the encoding is already using 100% of the bit rate. And the opposite situation: if a complex signal lasts long enough, all the saved bits are taken from the repository (gradually) and then encoding is done using now 100% of the bit rate.

ABR: Explanation

You could say that the reservoir does a good job with its main function – accumulating “extra” bits during simple passages and issuing them as additional bits when encoding complex passages, if not for one “but”: it has a finite and additionally very limited size, which means that it can only be stored up to certain limits and consequently also until the tank is empty. It is in order to eliminate this major tank drawback that the ABR was developed.

The main difference between ABR and CBR is that in CBR all frames must be the same size (that is, the bitrate for all frames must be the same), but in ABR this restriction is removed, respectively, there is an opportunity to use an almost infinite tank instead of the standard, very limited in size. “virtual” reservoir. Does it look like this.

ABR: mechanism

Suppose user specified ABR mode and a certain bitrate B (user can specify absolutely any bitrate from 32 to 320, even not from standard bitrate grid, for example you can specify 129 as the rate Average Bit Rate). AND

Why are video files growing too big in 2021?

Why are video files growing too big in 2021?

VideoHeight

There are many factors when it comes to creating multimedia content in 2021. Creators are at a stage where high definition falls short of high standards and people are always striving for the best possible results when it comes to quality of the media. With this in mind, as you work out your development plan, you need to consider the size of the videos you will create and how you will deliver them globally to your team and audience.

Video Height

It’s safe to say that if you dive into this blog post, then you are the creator of it. The purpose of this publication is to provide new or expanded information to creators in the Broadcasting industry. We want to highlight the continued increase in the size of video files, as well as the decisions on how to handle this growth without losing quality or data. Let’s debunk the myth that you need to compress video files before transferring them. There are solutions available in the streaming industry that allow you to use your large video files even when working on a remote production team. Today we will see what is happening with these video files and how you can estimate the size of your project and its transfer time.

Video length …

When creating a storyboard for your content, the first thing to consider is the length of the media file. Thinking of developing a feature film? Maybe an e-learning video course? This factor plays an important role in determining the size of your file, as it is the backbone of your content. Naturally, the shorter the duration, the smaller the size of the video that can be estimated.

Video Resolution …

Looking for the ultimate in sharpness, 8K or 4K? Or are your standards lower for your content? The question you should always ask yourself at the beginning of your project. This is important to know before you start filming, as you may need to purchase special tools to get your content to the level of quality you want. For example, you may need to purchase certain cameras, editing tools, and transfer software. There are tools that give you various resolution options. FileCatalyst Solutions lets you work without limiting your creative flow, as you can stream large video files around the world at an accelerated speed. Video quality ultimately affects the video file size in terms of pixels – the higher the quality of the movie, the more pixels make up the image. Higher quality results in a larger file size, while a larger file size makes transfer more difficult.

Video format …

Your video format also plays an important role in the size of your video file. There are two main components of a video format: codec and containers. Codecs refer to the process of compressing a file, and a container specifies how a video file is held together and displays it via the type of file extension (eg .mov, .mp4, .avi, etc.) . complications that can arise when compressing a large video file. Let’s say you created a 2 hour 8K video, to reduce its size, you have to compress it. In this process, the probability of data loss is high. “Video compression applications work by searching for duplicates in a frame and saving them from frame to frame. For example, a patch of blue sky is the same as another patch of blue sky. The blue section runs through each frame. With a high compression ratio, this becomes clear. ”

Solutions that eliminate the need for compression when working on a project are very useful. Its overall quality remains unchanged and there is virtually no transfer latency.

Video Frame Rate …

A quick way to analyze the size of the video you are working with is to find out the frames per second (FPS). The higher the FPS, the better the quality of your video. Here’s a cheat sheet that we created to help you understand this concept.

For the purposes of our diagram, suppose the standard frame rate is 25 frames per second, compressed with the BluRay H.264 codec to create an .mp4 file.

So now that you have an estimate of your video file size, let’s tune it in to understand how long it will take to transfer it.

It doesn’t matter if you are a company or a startup, the point is that there are always other teammates involved in creating video files.

Download all Netflix movies in one second.

Download all Netflix movies in one second.

Imagine the opportunity: download your entire Netflix movie library in less than a second. Unfortunately, real users won’t see this anytime soon, but scientists and specialists from the UK and Japan have set a new record for the speed of data transmission over the Internet using a fiber optic channel. The indicator was 178 Tbit / s or 178 million Mbit / s.

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In comparison, the fastest commercially available Internet today is used in Japan. There, the connection speed can reach 10 Gbps. Even the high-speed computing network of the Energy Sciences Network, which serves the scientists of the US Department of Energy and its employees around the world, is capable of delivering only 400 Gbps at its peak.

Scientists and engineers from Japan’s KDDI Research, University College London, and Xtera’s Submarine Communications Cable Installation Service set a new data rate record. Together they have developed new technologies that allow more data to be transferred using existing fiber optic infrastructure.

In most cases, the current capabilities of fiber optics allow transmitting a signal with a frequency of up to 4.5 THz, some innovative solutions, which are just beginning to be introduced in commercial operation, allow increasing the bandwidth to 9 THz. In turn, the new system allows to transmit signals with a frequency of 16.8 THz.

To set a record in the data transmission speed, specialists have applied various technologies to amplify the signal power, based on the geometric modulation method of the constellation of signals. Allows you to minimize the possibility of signal distortion during transmission by using patterns of signal combinations that allow you to more effectively use the phase, brightness, and polarization properties of light, as well as manipulate each length of single wave.

Since this technology can use existing fiber optic infrastructure to operate, it will be much easier and cheaper to integrate for commercial use than other experimental developments in this area. It is enough to upgrade the signal amplifiers located at a distance of 40 to 100 km from each other, without changing the fiber optic cables themselves. The researchers explain that the installation of an updated signal amplifier will cost around $ 21,000, and the cost of laying a kilometer of fiber optic cable in an urban setting can reach $ 593,000.

What is the bit rate in a Mp4?

What is the bit rate in a Mp4?

Mp4 Bitrate

Bit rate, also known as data transfer rate, is measured in seconds and determines the rate at which data travels through a communications network. Both video and audio have bit rates, and understanding what that is will help you better deal with your media.

Mp4 Bitrate

1. What is video bit rate (MP4)?

Video bit rate is defined as the number of bits that are processed and the unit is measured in bits per second. This is the speed at which the video is streaming at any given time. The higher the bitrate of mp4, the greater the data transfer at any given time. The exact bit rate of a video can be determined based on the device it will be played on. Good quality video on the web has a bit rate of about 2 Mbps, while standard definition DVDs have a bit rate of 6 Mbps.

2. What is the audio bit rate (MP3)?

The audio bit rate is defined as the number of bits that are used for the playing time per unit to represent the audio after encoding the source. It is defined as the degree of compression used to encode files in the audio aspect. The higher the MP3 bit rate, the better the sound quality and file size.

Part 2. How to choose the right bitrate for your video / audio
After examining the definition of video and audio bit rate, you should know how to choose the correct bit rate for your video or audio files. Since bit rate is related to the quality and size of your video and audio, it is important to choose and change the bit rate for your file. The two most frequently asked questions are listed below:

1.What is a good 1080p bitrate to upload to YouTube?

For YouTube uploads, the recommended video bit rate for a 1080p file is 8 Mbps for standard frame rates (24, 25, and 30). For high frame rates (48, 50, 60), the recommended bit rate for 1080p files is 12 Mbps.

2. What is the best bit rate for iTunes Audio?

Music files in the iTunes store are encoded in 256 kbps AAC by default. Previously, the bitrate of an iTunes song was 128 kbps and now it is 256 kbps. AAC codec files support up to 320 kbps.

Part 3. How to Change Video Bitrate with Simple Steps
There are many ways to compress a video, for example change the video resolution, trim the unwanted part, and convert the video format. However, changing the video bitrate is also a good option.

Media containers and their formats (Part 2)

Media containers and their formats (Part 2)

MEDIA CONTAINER

MKV (Matroska or Matryoshka) is the most popular multimedia container format that meets all modern requirements. Mainly focused on the H.264 codec family. Its main features include:

OSD menu creation;
divide the content into chapters;
fast backward through the file;
switch “on the fly” between audio and video tracks, as well as subtitles.
Therefore, it is a package that can contain many video, audio and subtitle sequences, allowing you to store a movie with all the additional materials in a single file, while providing a high level of navigation through the multimedia content. . It is also worth noting that MKV has high error resistance, modular scalability, and supports streaming materials over the Internet.

The wide popularization of this format is facilitated by the fact that it is an open source project. That is, for personal use, it is completely free. Currently, the most commonly used files with the “.mkv” extension are high definition video files, typically with multiple audio tracks and channels of subtitles.

MP4 (MPEG-4 Part 14) is another modern file format for storing digital video and audio streams, which is part of the MPEG-4 standard. It has almost all the same features as MKV. But MP4 has an advantage: files in this format can be played on almost any device, from smartphones to game consoles. MKV, in addition to personal computers, is compatible only with the most modern media centers.

Don’t forget the fact that MP4 is a “native” format for all Apple products from iPhone to Mac. So if you are a fan of “apple” iron, then it is better to collect and store your collection of home videos in MP4.

It should be noted that the MP4 container, unlike MKV, has a number of limitations and cannot contain video of the MPEG-1, MPEG-2 and WMV standards, as well as audio in AC-3 (Dolby Digital) and WMA formats.

VOB (Versioned Object Base) is the main container used to store multimedia content on DVD. It can contain multiple MPEG-2 video streams, up to nine audio tracks, up to 32 channels with subtitles and an OSD.

FLV (Flash Video) is a media container used to place and stream video clips on the global Internet. Used by many of the major video hosting services such as RuTube, YouTube, Vimeo, Flickr, and others. The video stream in the FLV file is generally encoded using the H.263 or H.264 codecs, and the audio is MP3 or AAC.

MOV is a file format developed by Apple to store videos, graphics, animations, and 3D. It owes its appearance to QuickTime media playback technology.

TS and M2 TS are specialized containers for storing HD video. TS is used in IPTV and DVB digital television transmission. It is true that this container cannot contain subtitles at all. M2TS is a standard container for Blu-Ray video, which can include video and audio streams provided by the BD-ROM standard, as well as subtitles in PGS graphic format.

Media containers and their formats

Media containers and their formats (Part 1)

Container Formats

Like any other digital information, video is stored on disk in the form of files, or as they are also called, media containers that contain video, audio, and other streams, as well as metadata. At any time, you can take, for example, video or audio tracks from the container, recode them and put them in another container, that is, change the format of the video file. Multimedia containers can be of different types (formats) and the file extension indicates which type they belong to.

MEDIA CONTAINERS

Even though most of the containers are bound to a specific format, some of them can store videos in completely different standards. For example, a file with the AVI extension can contain clips in MPEG-1 and MPEG-2 or MPEG-4 formats. What then influences the type of container?

Of course, to a greater extent, the quality of the movie is determined by the codec and parameters that were set during compression. But a lot also depends on the container. Various types of video files have certain requirements and restrictions regarding the number of audio tracks, subtitle channels, types of codecs used, as well as compatibility with consumer players and players.

Now, let’s take a look at the most popular video file formats and take a quick look at their advantages and disadvantages.

AVI (Audio Video Interleave) is the oldest and most traditional of all types of media containers, first used by Microsoft in 1992. It can contain video and audio information compressed using various combinations of codecs. Therefore, AVI files with external similarity can be very different in their internal “padding”, and to accurately determine their content, you will need to use special programs (for example, VideoToolBox).

Strictly speaking, this container has been outdated for a long time and has a number of serious drawbacks: the impossibility of containing mixed videos (for example, NTSC and PAL) and alternative audio tracks, the lack of timestamps and frame rates, the lack of normal operation with subtitles, poor support for modern codecs, etc.

However, this old man does not want to withdraw in any way, because a large amount of multimedia content on the network is still distributed using this format. The secret of such longevity, most likely, is the versatility of AVI, although on the other hand this is also its disadvantage. Sometimes you have to sweat a lot to open an AVI file created with exotic codecs.

Digital Video, its main features

Digital Video, its main features

digital video

Until recently, few people could have imagined that with an ordinary home computer it would be possible not only to watch your favorite movies, but also to create your own video library, digitize the content of old videotapes, edit family videos, and even create your own. movie masterpieces.

DIGITAL VIDEO

It all started in 1992, when IBM and Intel developed the Indeo software technology (short for Intel Video). With its help, users have the opportunity to digitize video and create video files on a PC, with subsequent playback on the monitor screen.

Initially, digital video was an analog signal converted to digital format. Furthermore, the conversion procedure itself inevitably led to a certain loss of quality. Today, VCRs and old VHS cameras are a thing of the past, and modern digital video cameras, DVD and Blu-Ray players, which allow you to receive a signal immediately in digital form, rule the ball. And analog television is gradually giving way to more progressive digital.

Key features of digital video
Digital video has five main characteristics: screen resolution, frame rate, color depth, bit rate (video transmission width), and image quality.

Screen resolution (resolution): indicates the number of dots (pixels) horizontally and vertically that make up the image (video frame) on the screen. When recording resolution, the value of the number of dots per line (horizontal resolution) is indicated first and then the number of lines involved in the image (vertical resolution). For example, for the European PAL video standard, the frame size is 720×576 pixels, for the North American NTSC standard – 720×480, for high definition video (HD 720p) – 1280×720, and for the new HDTV standard (Full HD) – 1920×1080 pixels. As you probably understand, the higher the screen resolution, the better the video quality.

The frame rate is a value that indicates how many frames are changed per second. The standard video playback speed is considered a value equal to 30 frames / s. For cinema, this figure is slightly lower and amounts to 24 frames / s.

Color depth (color resolution) is a characteristic that indicates the number of colors that can participate in the formation of a video image. The number of colors in digital video is measured in bits. So 1 bit can take two different values (0 or 1) and it only allows encoding two colors (usually black and white), respectively. With two bits, you can encode 4 colors (2 2 = 4), with three bits – 8 colors (2 3), four – 16 (2 4) and so on.

Typically, color resolution is described by special color models. In computer technology, the RGB (red-green-blue) model is used, which can be represented by the following most common color depth modes: 8-bit (256 colors), 16-bit (65,536 colors), and 24-bit (16,777 .216 colors). By the way, the human eye, according to various opinions, can perceive 5-10 million shades of color.

Bit rate (video stream width): Shows the number of video bits processed per second of time. In other words, this is the video transmission speed, which is measured in megabits per second (Mbps). The higher it is, the better the quality. For example, for the DVD video standard, the bit rate is about 5 Mbps and for the HDTV format, it is already 10 Mbps. By the way, most of the time the bit rate value is used to evaluate the quality of the video transmitted over the Internet.

Image quality is a characteristic designed to evaluate the quality of processed video compared to the original and is determined by a set of values for resolution, color depth, and video transmission speed.

Compression standards
One minute of pure, uncompressed and digitized sound takes up about 10MB on a computer’s hard drive, as a result of which, for the vast majority, music files are stored in a compressed form to save space. How long does a minute of uncompressed video take? For example, to place a 60-second video with a rate of 30 frames per second, a resolution of 720×576 pixels, and a color depth of 16-bit, you will need approximately one and a half gigabytes of free disk space. And this without taking into account the audio track. After these numbers, it is probably not necessary to explain why digital video is stored on our computers exclusively in compressed form.

There are several dozen popular compression formats that use different compression algorithms.