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什麼是編解碼器(codecs):視訊編解碼器(video codecs)的前世今生
Codecs Explained: Past, Present, and Future State of Video Codecs

Codecs Explained: Past, Present, and Future State of Video Codecs

2022-06-12

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Codecs are the building blocks of all digital media. Without them, we would virtually have no media, from still images to videos and audio. You have probably heard the term codec when discussing different file formats, but do you really know what codecs are? Probably not as well as you will by the end of reading this article.

This guide will introduce you to codecs and then take a deep dive into video codecs, the timeline of video codecs, and what the future holds.

What are Codecs?

According to the Oxford dictionary, a Codec is described as a device or program that compresses data to enable faster transmission and decompresses the received data. The term codec is a combination of encoder and decoder (or possibly compressor and decompressor hence Co-Dec).

The main purpose of Codecs is to facilitate the storage and transmission of digital media because, in their raw form, they require preposterous storage space.

According to calculations by Mozilla, when uncompressed, a 2-hour movie would take up to 1.79 TB of storage. Now imagine the amount of bandwidth that would be needed to transmit these uncompressed media over a network. That is where codecs come in during the creation, editing, and delivery of media files. Codecs aim to deliver an acceptably accurate image at a fraction of the original file size.

What are Video Codecs?

A video codec is a hardware or software that compresses and decompresses digital video to make file sizes smaller and storage and distribution of videos easier. Codecs also optimize files for playback on various devices.

When it comes to video encoding, video codecs play a crucial role. Video codecs apply algorithms to the video file and create a replica of it that is compressed for storage and transmission and later decompressed for viewing. There are essentially two types of video codecs: lossless and lossy. Lossless codecs maintain the originally captured data after decompression while lossy codecs produce high-quality compressed versions of the original by discarding unnecessary data.

Lossy codecs are the most common today because they lower data rates to a reasonable level while still producing high-quality videos. The shortcoming of lossy codecs is that the lower the data rate, the less the decompressed file looks or sounds like the original because of significant data loss during compression.

Video Codecs & Video Containers, What are the Differences?

Put simply, video codecs are the method of how the video is compressed and packaged. Common codecs are  H.264, VP9, HEVC, AV1, etc. We will cover this in more detail later. Video container, as its name suggests, contains a group of video data such as video, audio, metadata, codecs, and so on in different formats. It is also known as video format or file extension. Common video container formats are MP4, MKV, FLV, MOV, etc.

The Development Timeline of Video Codecs

We have made massive strides since the early 1990s when the Moving Picture Experts Group standardized the MPEG-1 coding standards. Most basic concepts of video coding such as transform coding, entropy coding, motion estimation, and compensation were developed earlier in the ’70s and ’80s. The MPEG-2 codec shortly followed and it was historically used for SD and DVD.

Within the next couple of years’ numerous codecs were standardized with the likes of MPEG-4, H.263, AVC (H.264), HEVC (H.265), AV1, Theora, and VP9 following. In the early 2000s, MPEG-2 became the dominant video codec and was exclusively used to compress television broadcasts and DVD movies.

Fast forward a few years and the H.264 or Advanced Video Coding (AVC) became the most popular video codec. H.264 allowed the rise of high-definition video and facilitated the introduction of 720p and 1080p resolutions by YouTube back in 2008 and 2009 respectively. Because of its extensive compatibility, most content on the internet is still encoded in H.264 codec.

High-Efficiency Video Coding (HEVC) or H.265 was the successor of the popular H.264 codec and it came with new ultra-high-resolution features. HEVC enables Ultra HD, 4K, and 8K video. However, the adoption of H.265 was stunted by licensing and royalty fees among three different entities which means it failed to gain as much traction as its predecessor. Even now, major web browsers like Chrome, Firefox, and Edge do not support HEVC at all.

The Next Generation of Codecs

The patent and royalty issues surrounding HEVC prompted Google to develop an open-source, royalty-free alternative to H.265 known as VP9. VP9 is supported by virtually all browsers, mobile devices, and most smart devices. VP9 is suited for Ultra HD and 4K video which has made it popular with YouTube and Netflix for some of their content. In terms of compatibility, it comes second only to H.264 while providing more advanced and higher-quality compression.

AV1 is one of the newest kids on the block and is an open-source, royalty-free codec developed by the Alliance of Open Media. According to a test by Facebook, AV1 offers 50% better compression than the popular H.264. Currently considered the codec of choice for streaming media, it is supported by Netflix, Google, Amazon, and YouTube. As a relatively new codec, hardware-level support is still quite low but it is projected to rise in a few years.

Conclusion

There you have it; all you need to know about codecs! It is highly difficult to establish a clear winner in the codec domain given that each codec has different properties and every broadcaster or institution has a different infrastructure and legacy systems.

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