Many readers asked me why the video format for drones are MOV and MP4 and what MPEG-4AVC/H.264 means.
This article will answer your questions.
About Drone Video Format
This paper used many materials and data on the internet for your reference.
Different from other files, video files are actually combinations of videos and audio files (some even include subtitles). Thus, apart from common file format, there are also encapsulation format and coding system. You should start from these three concepts to know video format.
File Format: video filename extension.
Encapsulation Format: container for storing video files.
Coding System: coding rules to compress/restore digital videos
It must be very confusing for you. So how to better understand the relationship of these three concepts? I was inspired by the two-flavor hot pot.
The two-flavor hot pot normally consists of a metal pot, spicy soup and clear soup.
You can imagine the video format as a two-flavor hot pot.
Generally the two-flavor hot pot has both spicy soup and clear soup with a divider in the pot.
Let’s imagine the spicy soup as the video: the side dishes (such as pig bags, beef tendons and meatballs) can be seen as video coding system.
Let’s imagine the clear soup as the audio: the side dishes (such as Chinese cabbages, mushrooms and white gourds) can be seen as audio coding system.
Then the combination rules for side dishes in spicy soup and that in clear soup can be seen as the encapsulation format: as long as you have decided the encapsulation format (for example, if you decide to choose a beef hot pot), then your choices of side dishes for the spicy soup and clear soup will be limited.
The file format is just a Windows filename extension for relevant program correlation. You can change the suffix .mp4 into .avi without changing the encapsulation format.
Similarly, you can change the two-flavor hot pot’s shape as long as it can hold two different soups.
Now it is easier to understand their relations.
With the same pot, such as a 32cm-diameter two-flavor pot with a hand grip, you can make a mutton hot pot or beef hot pot (encapsulation format). In a beef hot pot, you can have various choices of side dishes such as meatballs, sliced meat, meat loafs, corianders, vegetables and more (coding system).
After all, for the foodies (video players), the side dishes (coding system) comes the most important, following by the hot pot name (encapsulation format) and the pot (file format) successively.
To be specific, taking the file format .MPG as an example, it has different encapsulation formats such as MPEG-1, MPEG-2 and MPEG-4. And the encapsulation format MPEG-4 can have various coding systems. Therefore, the video files are mainly differentiated by their coding systems.
Having known the relations of file format, encapsulation format and coding system, I will introduce their detailed features in the following.
File Format
File format refers to the video filename extension for correlating the files with corresponding software. For example, if you click the file 1.doc, it will be opened by the Word instead of Photoshop. But if you change the filename to 1.psd, it will be opened by the Photoshop (though it can’t be read by Photoshop). Common video file formats include .MP4, .MOV, .AVI, etc.
If your video player can support these formats, the video can be played even if you change the filename from .AVI to .MP4 or .MOV.
Encapsulation Format
Encapsulation format can be seen as the container for video files (or even subtitles), which specifies the organization, layout and storage ways of these contents. The encapsulation format mainly features the function that can allow you to drag the progress bar while watching the videos. While the encapsulation format filenames are similar to that of file format, not all file formats can be stored in encapsulation format. The corresponding relations between them are as below:
MP4: official container format to store video files with a wide range of encoding ways.
MKV: open container format that can hold almost all coding systems. Now most HD movies are stored in MKV format.
AVI: with a long history, AVI format’s outdated architecture can no longer adapt to new coding systems.
RMVB: closed and standard container format to store RealVideo encoded videos, which has been obsoleted.
Time flies. The film formats have changed from .RMVB to AVI then to MKV over the years.
Coding System
Coding system basically refers to the compression standards because the videos are compressed/restored through coding/decoding.
These standards are mainly developed by ITU-T and ISO. The commonly used standards include H.26X series (ITU-T), MPEG series (ISO) and AMV, AVS, REALVIDEO, VC-A, WMV, etc. The current commonly used standards are H.264 and MPEG-4 AVC.
ITU-T is the abbreviation for International Telecommunications Union – Telecommunication Standardization Sector. The subordinate VCEG (Video Coding Experts Group) is mainly responsible for the video standards used in real-time communication field, such as H.261, H263, H263+ and H263++.
ISO is the abbreviation for International Standards Organization. The subordinate MPEG (Motion Picture Experts Group) is mainly responsible for the standards used in video storage, radio and television and network transmission, such as MPEG-1 and MPEG-4.
The ITU-T and ISO standards and development are shown in the following graph (the red dotted part refers to the standards jointly developed by them):
Both ITU-T and ISO have been bringing out their own video coding standards independently, but neither of them ever had absolute advantages. The most influential standards such as MPEG-2, H.264/AVC and H.265/HEVC are cooperatively created by them.
Thanks to their cooperation, the current unified coding standard is MPEG-4 AVC/H.264. However, ITU-T names it as H.264 and ISO/IEC names it as MPEG-4 AVC.
In the near future, we will have the HETV/H.265 code, which can enable smaller file size and higher resolution ratio (8192×4320, 8K) compared to MPEG-4 AVC/H.264. HETV/H.265 is the next-generation video coding standard.
At present, DJI Inspire 2 has taken the lead to offer H.265 video format as well as two RAW formats (Apple ProRes and Adobe Cinema DNG) for professionals to choose, elevating the image quality to a new level.
Summary
In conclusion, there are three reasons for using the MPEG-4 AVC/H.264-standard MP4/MOV format:
- MPEG-4 AVC/H.264 is the currently most widely used coding system with high efficiency.
- MP4/MOV format is the most common encapsulation system for Windows/Mac platforms and almost all hardware can support this format.
- The MPEG-4 AVC/H.264-coded MP4/MOV can reach a better balance in image quality and file size.
In future, we expect that more and more computers and mobile phones can support H.265 and that more and more drones can support H.265 to bring us better image quality and smaller file size.
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