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Video file formats / formats Part 3

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Video file formats / formats Part 3

Incidentally, the existence of some half-finished frame rates is due to technical restrictions in the transition of television transmission from black and white to color.

In fact, for applications other than broadcasting, 30 fps and 60 fps are often used.

On some platforms, the upper limit of the frame rate of the videos that can be sent can be set to 30 fps, but higher frame rates are still progressing, such as the video recording function of smartphones and YouTube that supports 60 fps. Super Hi-Vision, which is being developed as a next-generation streaming standard, has an even higher value of 120 fps.

1-5. Field order (drawing method)
There are two main types of video drawing methods, “progressive” and “interlaced”.

The drawing method is often expressed as a set with the vertical size of the resolution or the frame rate (or the number of fields). For example, 1280 x 720 progressive is “720p”, 1920 x 1080 interlaced is “1080i”, 24fps progressive is expressed as “24p”, 60-field interlaced is expressed as “60i”, and so on.

The video is made up of a collection of many points, and the points are divided into a block of horizontal lines (this is called a scan line) and displayed according to the drawing method. There is a difference in how this scan line is displayed between progressive and interlaced.

Field order
Currently, most of the media like YouTube recommend the progressive format, so it is good to remember that you basically use the progressive format for WEB videos.

Therefore, in progressive, the scan line of an image is twice as large as that of interlaced, so that the moving image becomes clearer. In interlaced, the moving image is less sharp, but the moving image is smoother with less data. .Can be displayed in.

1-6. Bit rate
Bit rate is a unit that is also used in communication lines, etc., but in video, it is a value that indicates how many bits per second are used to represent video data and audio data, and the rate value of bits is ◯ bps., ◯ b / s, or ◯ bit / s.

If the bit rate value is large, the amount of data packed per second will be large, so the video and audio quality will naturally improve. On the other hand, if the bit rate value is small, the video and audio quality will be reduced, but the video capacity will be reduced.

The higher the resolution of the video, the more noticeable the detailed drawing will be, so higher resolution videos will require a higher bit rate.

Also, there are two main types of bit rates: constant bit rate (CBR) and variable bit rate (VBR). Constant bit rate (CBR) refers to a compression method with a constant bit rate and variable bit rate (VBR) refers to a compression method with a variable bit rate.

Since CBR always has a constant bit rate, it has the advantage that it is easy to predict the size of the video in advance, and it has the disadvantage of using many bit rates. On the other hand, VBR adjusts the bit rate according to the scene, so it can improve the image quality by file size, but it has the disadvantage that the file size cannot be predicted. Variable Bit Rate (VBR) is recommended for YouTube.

Also, in the VBR (file compression / encoding) encoding method, “1-pass encoding” is used to encode the content of the file without parsing, and an appropriate bit rate is assigned after analyzing the data before encoding. . There is something called “2 -pass encoding” for encoding. With 2-pass encoding, analysis is done in advance, so encoding takes more time, but can produce high-quality video.

Bit rate

2. Recommended format for each platform
With that in mind, let’s take a look at an overview of the recommended formats for each video platform.
* See official help for the latest and most detailed information.

2-1. Youtube
YouTube supports a wide range of file formats, but the help page has recommended encoding settings, so it’s a good idea to check that out.

Recommended encoding settings for uploaded videos – YouTube Help

2-2. Facebook / Instagram
Facebook also supports a wide range of file formats. AAC of 1080p or less is recommended for video and 128 kbps or more for MP4 audio. Consider the aspect ratio, such as screen occupancy.

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Video file formats / formats Part 2

Video file formats / formats Part 2

Files that are handled on a personal computer have an extension so you can see what kind of data they are.

For notepad it is “.txt”, for Excel it is “.xls” or “.xlsx” and for images it is “.jpg” or “.png”.

Video files have the same extensions, such as “.mp4”, “.mov”, “.avi” and “.mpg”.

For example, there are more than 10 types of video keys (= codecs) that correspond to the extension “.mov”. In other words, the extension in the video is just a guide to predict the content and keys.

Although it can be identified that it is a video file by looking at those extensions, the extension and the video file, and the video file and the key (= codec) are not one by one, so the extension is just a guide. . to show your identity Always makes it difficult to handle video files.

The main video files, extensions and codecs are summarized below. If you only know the extension and want to check the codec, you should use a software called codec checker like “MediaInfo” or “Vacuum Wave Lab SuperLite”.

Most of the major video players these days, like Windows Media Player for Windows and QuickTime Player for Mac, have a built-in key (= codec), and most of them can play videos with that software. However, keep in mind that some of them are not supported. You need to get that codec or get a player that includes that codec.

Video file format explanation Main extensions Main codecs
MP4 has a high compression rate and is very convenient, but it is difficult to determine the content because there are many codecs. The recommended format for YouTube is H264 mp4 format. .mp4 .m4v (Video) MPEG1 MPEG2 MPEG4 H.263 H.264 H.265 H.264 / AVC WMP9 (Audio) AAC-LC AC-3 MP3 HE-AAC VQ Apple Lossless
MOV A standard file for working with videos on Mac. It is based on MP4 and can also use the MPEG-4 video codec. .mov .qt (Video) MPEG-4 H.264 Motion JPEG (Audio) AAC MP3
MPEG-2 PS It is used as the recording format for DVD and the like. A standard based on the assumption that bit errors are small, created on the premise of storage media. .mpg .mpeg .mpe .m2p (Video) MPEG-1 MPEG-2 (Audio) MPEG1 Layer-II MPEG2 Layer-II LPCM AC-3
MPEG-2 TS The format used by many digital transmission standards around the world. Used in HDTV and Blu-ray recorders .mpg .mpeg .mp2 .m2p .m2t .mpt .m2ts .mts .ts .vob (Video) MPEG1 MPEG2 MPEG4 H.264 / AVC (Audio) MPEG1 Layer- II MPEG2 Layer-II MPEG4 AAC-LC LPCM AC-3 MP3
AVI Please note that the old format cannot be played if the file is incomplete and there are restrictions such as a maximum capacity limit of 2GB. There are a lot of codecs here too. .avi .divx (Video) MPEG1 MPEG2 MPEG4 Motion JPEG DivX 3-5 XviD (Audio) MPEG1 Layer-III MPEG2 Layer-III PCM AC-3
1-4. Frame rate
The frame rate is a value that indicates how many image frames (frames) are recorded per second, just like character reading, and the frame rate value is ◯ fps or ◯ f / s. I will describe it. In other words, if 30 images (frames) are recorded per second, the value will be 30 fps or 30 f / s.

The higher the frame rate value, the smoother the video will move, and the lower the frame rate value, the more choppy the video will be. In other words, the frame rate can be reformulated as a value that represents the smoothness of the moving image display.

The video on the right reproduces the difference in video depending on the frame rate.

The higher the frame rate, the better. A video with a large frame rate value will have a large number of recorded images, and of course the amount of data will also be large. In addition, there are limits on the human eye, the side of the screen that projects it, and the technical specifications on the middle side, so it is necessary to set it to a suitable value.

Typical frame rates currently used are 24 fps, which is used for filming and animation, 29.97 fps, which is used for television broadcasts in Japan, and recent consumer cameras. There are 59.94 fps conventional, etc. Furthermore, there are also 25fps mainly for Europe.

Video file formats / formats

Video file formats / formats

What you want to know before making a video

Just as images have resolutions and file formats, there are some fixed formats and specifications for videos. Naturally, moving images, moving images, have more elements to define in the specifications, and the mechanism is complicated.
In fact, people in charge of marketing and promotion, advertising agencies, etc., can often feel disgusted by observing the presentation rules of each company.
This time, to dispel the weaknesses of those people, I would like to present a few main points that need to be understood in the video specs and the optimal video specs on major platforms like YouTube and Facebook.

1. Six Points Defining Video Specifications
Now, I would like to explain the six main points in the video specs.

1-1. Resolution
Like still images, videos have resolution. Image resolution refers to “size” and “pixel density”, but for moving images, resolution refers to “horizontal x vertical pixel count”.

The resolutions of familiar things are 720 x 480 SD image quality for DVD, 1920 x 1080 full HD for Blu-ray and 1440 x 1080 for digital terrestrial broadcast (* The reason why the aspect ratio is different from other will describe later).

Typical resolutions include
Full HD (1920 x 1080) / HD (1280 x 720) / SD (720 x 480) / 4K UHD (3840 x 2160)
.

Video resolution
Cameras like the iPhone X support 4K video recording and major streaming services like Netflix and Amazon Prime Video support 4K distribution.

Recently, with the expansion of smartphones and the rise of vertical signage, videos with long vertical resolutions and square videos like Instagram have also appeared.

Some people have said that “Full HD resolution is enough”, but the screen has gotten bigger, the price of 4K TVs has dropped, the drawing power of the smartphone screen has improved, and 4K / 8K has been improved. it has been generalized mainly by the Ministry of the Interior. Issues and Communications: As various efforts are made in this regard, it is expected that further progress will be made on a higher resolution.

1-2. Pixel aspect ratio
The pixel aspect ratio, also called the pixel ratio, represents the ratio of the width to the height of the pixels that make up the video data, and you can set the expansion / contraction ratio of the video during playback. Be careful as it is easy to confuse with the old resolution (aspect ratio of the video itself).

In digital terrestrial broadcasting, due to the compatibility with the conventional SD format and the amount of data, data with a resolution of 1440 x 1080 (4: 3) and a pixel aspect ratio of 4: 3 is distributed and stretched on the side of the TV. When doing so, the appearance is 16: 9, but it’s okay if you think you are basically using square pixels (1: 1) in WEB video.

1-3. File format (container), codec
To understand the file format of a video, you need to understand what is called a “codec.”

Audio and video data are stored in a “video file”.
In addition, data is compressed and encoded (also called encoding) using a “codec” so that it can be processed more efficiently and more easily by personal computer software.

In other words, when a video is played, it cannot be played unless the data is decompressed using the same “codec” as the “codec” used when compressing.

Note that the codec cannot be identified by the file extension alone. When making a request to a production company, be sure to also specify the codec.

To make it easier to understand, we will use “codec” as “key” and “video / audio data” as “treasure box”.

There are two treasure chests in the video archive, each locked with a different key. That is, to open the treasure chest and play the video, the key (= codec) corresponding to each treasure chest is required.

If you lock with “Key A” when generating video data and “Key B” when generating audio data, the video will play normally if you don’t have “Key A” and “Key B” in your hand. You can’t do it and if you only have “Key A”, you won’t be able to play the audio.

Types of videos

Types of videos

MPEG-1

The MPEG-1 video compression format was developed by the Motion Picture Expert Group, an international organization that creates video compression standards. It supports a maximum frame resolution of 4095 x 4095 pixels at a frame rate of up to 60 times per second. However, a resolution of 352 x 288 is generally used, which corresponds to the quality of recording on a normal VHS cassette.

How is the information compressed in this format? Suppose we have the following scene: the car moves from point “A” to point “B”. The movement of the machine can be described by two parameters: the vector of movement from point “A” to point “B” and the angle of rotation around its axis. At the same time, the background remains unchanged or almost unchanged: the viewer is unlikely to pay attention to the vibrations of small branches near distant trees. So you can divide the frame into two components: the background, which is saved once and then replaced during all-frame playback, and the area where the car moves, will have to be recorded separately for each frame.

Digital video: an overview of formats

In MPEG-1 format, all frames in a movie are classified into three types: I, P, and B frames. The first type (I-frames, Intra Frames) includes anchor frames. Your images are saved in their entirety in JPEG format. For the predicted frames, only the differences from the previous i-frame are recorded, which requires much less disk space. For B-frames (bidirectionally interpolated frames), the differences with the previous and next I or P-frames are preserved (Fig. 2).

Digital video: an overview of formats

As a result, the compressed file size is approximately 1/35 of the original. This means that an hour and a half movie with the quality equivalent to an analog VHS cassette in MPEG-1 format will fit on two CDs. For transmission over the Internet or in satellite transmission networks, this standard, of course, is not suitable. But there have been many consumer video CD players that work in this format (and they are still being produced now, by the way).

MPEG-2

MPEG-2 is an additional extension of MPEG-1. The recommended frame size has been increased; it is now 1920 x x 1080 pixels, added support for six channel audio. However, playing video in this format requires more processing power from your computer.

It should be noted that work was underway to create the MPEG-3 standard (not to be confused with the now popular audio compression format: MPEG-1 Audio Layer 3). It was supposed to become the basis for HDTV digital television systems. But the work was interrupted, because the necessary requirements for HDTV were implemented in the form of small extensions of MPEG-2.

This format is now quite widespread in the West: it is used to transmit video through satellite channels and digital cable networks, in addition, all DVD video discs are recorded in this format.

MJPEG

In fact, MJPEG (Motion JPEG) is a transition format from compressing normal photos to compressing videos. Each frame is recorded in JPEG format and then placed in the footage. MJPEG is mainly used in video editing cards like Fast AV Master, MiroVideo DC50, etc. You can reduce the video stream from 30MBps to 6MBps. For use in home video players, this standard is not very suitable due to the low compression ratio (5: 1) and the lack of means to synchronize video and sound.

MPEG-4

The MPEG-1 and MPEG-2 formats did not provide a real possibility to transmit video over the Internet and create interactive television based on them: the file size was too large. To drastically reduce it, as well as implement other functions necessary for video transmission, work has begun on the specifications of a new format: MPEG-4. In fact, it does not focus so much on video compression as on the creation of so-called “multimedia content”: the fusion of interactive television, 3D graphics, text, and so on.

As for the video itself, the most important innovation was the further improvement of technologies for decomposing a scene into objects and algorithms for their effective compression. Thus, for example, when compressing a video recording of a tennis match, most of the frames can be conditionally decomposed into images of the stands (background) and the players.

Video format comparison: MOV, FLV, MP4 and 3GP

Video format comparison: MOV, FLV, MP4 and 3GP

Each video file format has its own unique characteristics, which make it ideal for specific uses. This fact forces the user to have to choose between them more and more frequently. The most important criteria in making this decision is which characteristics of the file types best suit your specific needs. To help you choose the best type of video file, here is a list of the pros and cons of the most popular video formats.

The .mov video format

The MOV video file format was developed by Apple with the aim of bringing clear benefits to users. One of these advantages is the high quality of MOV videos. Cinema purists and filmmakers who want to create long digital movies, in particular, are determined by the quality preservation properties of the MOV format. When working with MOV files, optimal video quality will be maintained throughout the project. Although MOV is closely linked to Apple, the files can also be opened with Quicktime Player on Windows.

A major problem with MOV is the lack of support from the various media player applications. Many users have to download new software before they can play MOV video. Also, the files are very large, which requires more hard disk space. This can slow down old hardware.

Ultimately, .mov was designed for a specific group of users, especially those who value high video quality. Even if these files are generally used less frequently, they are of great value to a small target group.

The word ‘video’ is made up of many letter tiles.
With the right video format, projects can be implemented smoothly.

The .flv video format

The FLV video file format stands for Adobe Flash Videos. It is the most widely used type of video file on the Internet. The reason for the enormous popularity of .flv is that the format works optimally in all major browsers. Therefore, leading video portals like YouTube also use Flash videos by default. Another reason for the frequent use of FLV video files is that it is suitable for various video formats, including commercial ones.

There is also a downside to the FLV format: if a lot of Flash videos are hosted on a website, it can get slower overall. This is especially likely to be felt by visitors with slower Internet access. This is still a major problem at this time. As the Internet becomes more accessible, this concern will lessen in the future.

A man is editing a video on a laptop.
The FLV video format sadly affects the loading times of websites.

The video format .mp4

The MP4 video file format offers high-quality video. Unfortunately, the format is not ideal for a single task. But that doesn’t mean that these files don’t have many advantages as well. In fact, MP4 files are so small that they are ideal for storing in a video asset management system. Even at such a small size, the video quality is amazing. They are also great for sharing videos due to their high browser compatibility.

Therefore, it is quite paradoxical that the MP4 format is used as the standard in most photo and video cameras, as it scares filmmakers so much. The reason for this is that .mp4 files do not edit well. Without the proper properties that allow for proper editing and good editing, the MP4 video format does not meet the requirements of one of the potentially most important user groups.

A hand holding a camera lens in the forest.
MP4 videos retain high quality despite their small file size.

The .3gp video format

The 3GP video format corresponds to the Third Generation Partnership Project and is the associated file extension. It can be opened with many programs, is inexpensive in terms of memory requirements, and optimally protects data. It is ideal for mobile devices that cannot cope with high traffic when streaming video to each other.

Also, the .3gp file type has a dominant position in relation to video transmitted via text messaging services. This will continue despite certain weak points.

A key problem with 3GP relates to compression and the difficulties it presents. Users who care about maintaining video quality will be amazed at the end result of compression. Although this deficit is a necessary evil for the sake of functionality, many users still find it negative.

Get familiar with the big differences between video file types. This will allow you to make the right decisions for a successful implementation of future projects. Once you have a solid understanding of video formats, consider using a digital asset management system to manage your video files.