Once I needed to record a video clip and post it online. At that time I didn't know much about video formats, so I had a hard time choosing a format for saving the recorded video (I was recording a video lesson). All this prompted me to review the most popular video formats and finally get to the bottom of this question.
Who will be interested in this article: all those who are not involved in video editing and are not familiar with the basic video formats, the article deals with the difference between media container and codec.
What you will learn: what is media container and video codec, you will be able to easily navigate in modern video formats, distinguishing them by their extensions.
Theory and terminology
Video is simply a series of images recorded one after another. As we know, video was recorded long before the first computer, i.e. in analog form. This imposed great restrictions on its subsequent processing and editing. Until the early 1990s, this type of video recording prevailed. Later, digital video recording and storage technologies were developed.
It gave a big boost to the development of not only cinematography but also home video. It means the recording of videos and home movies became a very popular activity. All this, together with the development of computer technology, forced the developers to improve the technology of recording, storage, and processing of video information.
Just for the purpose of storing such information, various video formats were developed (at the moment they are numerous and it is very difficult to navigate in them), which are the main subject of this article.
The video format defines the structure of the video file, i.e. how the file is stored on the storage medium (CD, DVD, or hard disk).
Due to a large number of video formats, many people have started to confuse completely different concepts - "video standard", "video codec" and "media container". Let's find out what these concepts are.
Codec (CODEC = COder+DECoder / codec = encoder + decoder/ ) - software or hardware that converts video information into a stream of condensed data and vice versa.
A media container is a file format that stores information about its internal structure. A media container is actually a meta format because it stores data and information about how the data will be stored directly within the file.
We can draw some analogies between a media container and a zip archive. That is, a media container contains video and audio files inside itself, just like a zip archive that contains a JPEG picture that will be compressed using a certain algorithm. A special module in archives is usually responsible for information compression, while in media containers the role of this module is performed by a codec.
Any video file has at least two characteristics that determine how it is handled. These are the type of media container and the codec(s) used to encode the content.
The media container type determines how various data (video data, audio data, subtitles, service information, etc.) are written to the file. By knowing the container type, a program (such as a video player) can correctly extract data from it, synchronize audio and video data, etc.
Knowledge of the codec allows the software to retrieve the audio and video information contained in the media container from the encoded data stream.
Popular codecs are DivX, Xvid, H.264, Theora, Indeo, x264, and others.
Popular media containers are AVI, QuickTime, MPEG-4, 3GP, and others.
Below we discuss video formats in three categories: analog, digital and compressed video. Analog formats are already outdated, so their consideration was superficial. I could not exclude them from the review, because it is necessary to have an idea of the general picture. You can "skip" their consideration and go straight to the digitally compressed video formats.
Analog video formats
VHS (Video Home System) - the capabilities of this format were limited to a resolution of 240 television lines or 320 × 240 dots on a PC screen.
A VHS tape with a tape width of 12.65 mm and a speed of 23.39 mm/s was used, which had a recording time of 240 minutes at Standard Play (SP) tape speed and the lowest shooting cost. The record-playback mode was also capable of LP (Long Play) speed of 11.695 mm/s.
The main drawback of the VHS format is the low picture sharpness (240 lines across) and the drastic loss of quality with every re-recording. Later on, this video format was modernized several times. Particularly the VHS-Compact (VHS-C) and Super VHS (S-VHS) formats were developed. Now considered obsolete, VHS video cassettes were discontinued in 2008.
Hi8 - "Hi" is an abbreviation of English "High" and implies high image quality, and the second digit "8" indicates the tape width in the cassette, i.e. film width - 8 mm, speed - 28.695 mm/s. The video resolution is 400 television lines (TVL). An analog audio stream could be recorded on the cassette in two modes - mono and stereo. The maximum recording time was 180 minutes in SP (Standard Play) mode and 360 minutes in LP (Long Play) mode. The cameras were equipped with an S-Video connector for high-quality image output.
Hi8 XR (Hi 8 extended Resolution) is the same Hi8 but with increased resolution, i.e. an improved modification of the Hi8 format. The image resolution reached 440 lines horizontally with a lower level of color and luminance noise due to the extension of the luminance signal recording bandwidth to the audio signal area.
Both of the above formats (as well as VHS) are long obsolete and have been replaced by digital video formats.
Digital video formats
DV (Digital video) - In 1993, Sony, Matsushita (Panasonic), JVS, Hitachi, Mitsubishi, Toshiba, Sanyo, Sharp, Philips, and others formed the Digital Video Cassette consortium or DVC. Later abbreviation of the name was shortened to DV. Together, these firms developed a consumer digital video recording standard on 6.35 mm (quarter inch) wide tape. This format provides 500 lines of resolution. Digitization while recording is at 720 × 576 resolution.
Video and audio are separately recorded in DV format. This makes it possible to add audio after recording or editing or to re-record audio. The DV format provides the highest quality still and video recording and allows all data to be stored digitally on tape, memory card, or computer hard drive.
Mini DV (Mini Digital Video) is a digital semi-professional format created by simplifying and cheapening the professional DV format. It uses special cassettes Mini DV (tape width - 6.35 mm, speed - 18.831 mm / s), which are played either from a camera or on a special digital video recorder.
The recording duration per cassette is 60 minutes SP or 90 minutes LP. Mini DV has an image resolution up to 540 lines across (720 × 576 dots), supports CD-quality stereo sound (PCM stereo - 48 kHz / 16 bit / 2 channels or 32 kHz / 12 bit / 4 channels).
Compressed digital video formats
AVI (Audio-Video Interleaved), a technology by Microsoft, is the most common and least compressed of the video formats. Files created using this method have the extension .avi extension. Video and audio data is recorded into a single file on a disc in the following way: all data streams are divided into multiple equal parts (chunks) and then written into a single file, one after another.
The header is recorded first, and then the 1st part of the video and the 1st part of audio; then the 2nd part of the video and the 2nd part of audio, and so on. In other words, video and audio interleaved technology is used, which is how AVI (Audio-Video Interleaved) is actually defined. On average, one second of AVI images occupies about 2 MB on the hard disk.
Characteristics:
- ● Type - media container
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● Compatible codecs - DivX, Xvid, Indeo and others (for video) and MP3, WMA, and others (for audio)
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● File extension - .avi
QuickTime - "QuickTime" is both an Apple media player and compressed video technology that provides the ability to capture, compress, and play a wide range of digital video and audio content. QuickTime has three fundamental elements - the QuickTime video format (Movie file format), the Media Abstraction Layer, and a suite of embedded media services. The Media Abstraction Layer defines a set of service functions for creating, editing, and playing back digital material.
Among them:
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● time synchronization;
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● audio and video data compression and decompression;
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● format conversion, scaling, blending, and transcoding;
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● audio and video effects and transitions;
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● synchronization of reading and writing;
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● data capture;
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● data import and export.
The QuickTime program and codecs are used to play both your own video format (QT and MOV) and other most common media formats for digital video, audio, text, animation, and streaming video from the Internet. Supported formats include MP3, AVI, MPEG (including MPEG-4), AAC Audio, and Flash.
Characteristics:
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● Type - media container
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● Compatible codecs - Apple Video, H.264 and many others (for video) and Apple Lossless, AAC, MP3, WAV, and others (for audio)
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File extensions - .mov, .qt
MPEG video compression format family
The word "MPEG" is short for Moving Picture Expert Group, the name of an ISO (International Organization for Standardization) expert group working to develop standards for video and audio coding and compression. MPEG is often used to refer to standards developed by the group. MPEG technology uses streaming video compression, which does not process each frame individually (as it does with Motion-JPEG algorithms), but analyzes the dynamics of video fragments and eliminates redundant data.
MPEG-1 is a format (TV standard) for storing and playing back video and audio data on multimedia data carriers. Quality comparable to VHS video recording (352 × 228 (PAL standard) or 320 × 240 (NTSC standard) resolution at 25 or 30 frames per second, respectively). The format is used for recording Video CDs. Special software (codecs) is used to encode videos in MPEG-1 format.
MPEG-2 and MPEG-3 - MPEG-2 is designed to complement MPEG-1 and supports high-quality video streaming over high-speed digital channels. Media streaming rates of up to 50 Mbyte/s can be achieved. As a result, for movies created in PAL and SECAM, 720 × 576 resolution at 25 frames per second with an almost broadcast quality is supported. This format is suitable for all TV standards and is widely used for DVD recording. MPEG-1 and MPEG-2 are internationally recognized standards for video compression. MPEG-2 adds support for multichannel audio (Dolby Digital 5.1, DTS, etc.).
Contrary to expectations and predictions, the development of the MPEG-3 standard was merely an improved version of MPEG-2. The MPEG-3 format (not to be confused with the MP3 audio compression format) is now part of the MPEG-2 standard and is no longer referred to separately.
MPEG-4 - MPEG-4 defines the principles of digital media representation for three fields: interactive multimedia (including products distributed on optical disc and over the Internet), graphics applications, and digital television (DTV). It deals not just with media streams and arrays, but with media objects, which are the key concept of this standard.
When transporting the video picture is divided into component elements - media objects, the structure of these objects and their relationships are described so that it is possible to assemble them into a single video and audio scene. The resulting scene is composed of media objects merged into a hierarchical structure. Unlike previous MPEG standards which used to divide a frame into square blocks regardless of its content, MPEG-4 encoders operate on arbitrarily shaped integer objects.
Keyframes are not arranged with a prescribed regularity but are selected by the encoder only at the moments when a change in the scene occurs. Such branching algorithms of search and processing of objects of complex shape and in-depth analysis of frame sequences require considerably more computational resources for quality restoration (decompression) of this format image than in the case of MPEG-1 or 2.
The efficiency of MPEG-4 video compression makes it possible to fit a full-length film of one and a half to two hours' duration with good quality on a single 700 Mbyte standard CD-ROM. However, MPEG-4 movies still fall short of the quality of MPEG-2 DVD video.
MPEG 7 and MPEG 21 - Unlike previous MPEG family compression formats, MPEG 7 describes information represented in any form and is environment-independent.
The MPEG 7 compression format uses a multi-level structure for describing audio and video information. The highest level describes the properties of the file, such as the name, creator, creation date, etc. At the next level of description, the MPEG 7 compression format specifies the features of the audio or video information to be compressed, such as color, texture, tone or speed.
One of the distinguishing features of MPEG 7 is its ability to identify the type of information being compressed. If it is an audio or video file, it is first compressed using MPEG 1, MPEG 2, MPEG 4 algorithms and then described using MPEG 7. This flexibility in the choice of compression methods significantly reduces the amount of information and speeds up the compression process.
The key advantage of MPEG 7 compression format over its predecessors is that it employs unique descriptors and description schemes which, among other things, enable automatic allocation of information according to both general and semantic features associated with human perception of information. The procedure of data cataloging and retrieval is beyond the scope of this compression format.
The development of the MPEG 21 compression format is a long-term project called the Multimedia Framework. (Multimedia Framework.) Experts began working on the development of this compression format in June 2000. The first stages were to extend, unify and unite the MPEG 4 and MPEG 7 formats into a single generalized framework. It was envisaged that it would provide in-depth support for rights management and payment systems, as well as the quality of services provided.
Features
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● Type - family of video standards (includes media containers and codecs)
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● Compatible codecs - H.264 and others (for video) and AAC, MP3, WAV and others (for audio)
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● File extensions - .mpeg, .mpg, .mpe, .m1v; .dat and .m2v (VideoCD (VSD) and Super VideoCD (SVCD) formats - MPEG-1/2 compression standard); .vob (DVD video format, contains MPEG2 video)
Matroska is a project aimed at creating an open, flexible, cross-platform multimedia container format and a set of tools and libraries for working with data in this format. This is an open format that was developed as an alternative to the other AVI, QuickTime, and MPEG containers. A distinctive feature of this format is the possibility of using several audio streams in one file.
Characteristics:
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● Type - media container
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● Compatible codecs - H.264 and others (for video) and AAC, Vorbis, DTS, MP3, and others (for audio)
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● File extensions are .mkv (video with subtitles and audio), .mka (audio files), and .mks (subtitles)
Flash Video is a video format used for transmitting data over the Internet. It is used in Youtube, Google Video, RuTube, etc. The popularity of this format is largely due to the fact that it is supported by Adobe Flash Player, which is distributed as a cross-platform standalone application and as a browser plug-in.
Characteristics:
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● Type - media container
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● Compatible codecs - H.263 (FLV1), VP6 (FL4), H.264 (FLV5) (for video) and AAC, MP3 (for audio)
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● File extensions are .flv (usually)
Conclusions
As it turns out, 'getting to grips with this issue (the variety of video formats) is very difficult. Firstly, there are dozens of different video standards that are sometimes very different from each other. Secondly, due to "format wars" there appear new formats that are similar to each other but have peculiarities of their own. Thirdly, not all of the formats are widespread due to patents on their use, etc.
All this leads to the fact that now it is rather difficult to orient in this variety of technologies. Although there are some improvements (in particular in the development of MPEG standards) and hopefully they will be preserved. It should be noted that I have not considered in this review some less popular (in my opinion) formats - 3GP media container (used in mobile phones), ASF (Advanced Systems Format) - streaming video format developed by Microsoft, RealMedia - streaming video format by RealNetworks Products and Services.
We would also like to say a few words about video playback. Often there are problems when playing a particular video clip if the system does not have the appropriate codec to decode the video stream. This can occur due to the fact that the player is used, which comes with codecs of only one company, which can not use other companies' codecs due to patent prohibitions. This can be avoided by installing so-called codec packs.
But I prefer universal players which include almost all known video codecs. An example of such a player is TheKMPlayer. Thanks to it, I do not think about what codecs are installed on my system. My advice!
