Explaining Digital Video: Formats, Codecs & Containers

Introduction

Digital video files can have many different file extensions, including MP4, MOV, and MXF. However, the first thing to understand about digital video formats is that they're not defined solely by their file type. This makes digital video formats far more complex than, for example, image formats, where you can be certain that a JPG file is an image in the JPEG format. In digital video, a format is a combination of a video codec and a container.

Understanding Codecs and Containers

Codec stands for "coder-decoder" and refers to the algorithm used to digitally encode a video. A container, on the other hand, is a digital box or wrapper used to store video streams alongside related content, all in a single file. Therefore, it is the digital video containers that can be identified by their file extension, rather than the video formats themselves.

Today, a vast range of video codecs and containers are in use. Common codecs include:

H.264 (AVC)
H.265 (HEVC)
H.262 (MPEG-2 Part 2)
MJPEG
ProRes
DNxHD
DNxHR

Common containers include:

MP4
AVI
MOV
MXF
3GP
3G2
MTS
M2TS
TS

Examples of Digital Video Formats

To illustrate the complexity of digital video formats, consider a MiniDV tape. This medium can store video encoded with several codecs: standard definition consumer DV, professional standard definition DV cam, and high definition HDV. As such, just like a DV tape, you cannot infer a digital video's format just by looking at the file extension.

Digital video, much like a reel of movie film, consists of a series of still frames. Codecs digitally encode these frames, and some codecs use compression methods to limit file size. There are two main compression methods: intra-frame and inter-frame.

Intra-frame compression compresses each frame individually.
Inter-frame compression compresses frames by storing keyframes and delta frames, which represent only the incremental changes.

If you plan to edit your video, it's best to shoot it using an intra-frame codec as editing is generally easier and can result in higher quality output. Common intra-frame codecs include MJPEG, ProRes, DNxHD, and DNxHR.

Popular Codecs Explained

One of the most popular codecs in use today is H.264, defined by the Motion Picture Experts Group (MPEG) in part 10 of their MPEG-4 standard. H.264 is generally an inter-frame codec that produces relatively small video files. A more recent codec is H.265 (HEVC), which can provide similar video quality as H.264 while using half the data rate. However, H.265 requires more computational power, making it less suited for editing.

H.262 is an earlier codec still widely used for digital television broadcasts and DVDs.

The quality of the output also depends on the choice of the container, which is a digital box that stores the video as well as any accompanying audio streams or subtitles. Some notable containers include:

MP4: Widely used for both professional and consumer applications.
AVI: Developed by Microsoft to support audio and video interleaving.
MOV: Created by Apple for movie files.
MXF: Used in professional video production and distribution.

Combining Codecs and Containers

Video formats are often combinations of codecs and containers. For example:

AVCHD (Advanced Video Coding High Definition) uses the H.264 codec in an MTS or M2TS container.
XAVC-I and XAVC-L formats from Sony store H.264 video in an MXF container.

Even consumer DSLRs often do not declare a specific format, typically using H.264 or H.265 codecs in MP4 or MOV containers.

For final digital video files, while H.264 and H.265 in MP4 or MOV containers are most common among consumers, professionals often use MXF containers with codecs like ProRes or DNxHD for delivery.

Conclusion

In recent years, digital video has replaced film as the primary medium for capturing and distributing moving images. The choice of which codecs and containers to use can be complex, but understanding these fundamentals provides a solid basis for navigating the digital video landscape.

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Keywords

Digital Video
Formats
Codecs
Containers
H.264
H.265
MPEG
MiniDV
Compression
Intra-frame
Inter-frame
MP4
MOV
AVI
MXF

FAQ

Q: What is a digital video format?
A: A digital video format is a combination of a video codec and a container.

Q: What is a codec?
A: A codec, or coder-decoder, is an algorithm used to digitally encode a video.

Q: What is a container?
A: A container is a digital wrapper used to store video streams and related content in a single file.

Q: Which codecs are commonly used today?
A: Common codecs include H.264, H.265, H.262, MJPEG, ProRes, DNxHD, and DNxHR.

Q: What is MP4?
A: MP4 is a widely used digital video container that can store video encoded with various codecs.

Q: Which format should I use for YouTube uploads?
A: The recommended format for YouTube uploads is using H.264 codec with an MP4 container.