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A VIDEO COMPRESSION PRIMER Video compression can be complex, but it doesn’t have to be complicated. We step back to get an overview of the most essential element in digital video distribution
hat used to be a relatively simple proposition for broadcasters – delivering a single analogue or digital signal to one type of device – has become a highly complex series of technological tasks. Broadcasters, pay TV operators and OTT services must deliver video to every type of device now, from big HD and 4K televisions to mobile phones and tablets. The caveat: audiences expect video to look just as good on the smallest device as it does on the largest one. Today’s TV shows are shot at the same quality as feature films, quality that translates into a data rate that could be as high as 5TB an hour or more. Those files are far too large for even the fastest Internet connection to deliver consistently, and most consumer devices aren’t designed to play back these video source formats. So how do you stream premium content to viewers on smart TVs, mobile phones, or tablets – whether those devices are connected to Gigabit Ethernet, a cellular
network, or any connection speed in between the two? The answer: compress video files into smaller sizes and formats. The dilemma: enabling high-quality playback of these files on every possible type of screen. Codecs are the key to addressing size, format and playback requirements. A codec allows you to take video input and create a compressed digital bit stream (encode) that is then played back (decoded) on the destination device. There are two types of codecs: lossless and lossy. Lossless compression allows you to reduce file sizes while still maintaining the original or uncompressed video fidelity. Digital cinema files are generally encoded in a lossless format. The video files that you watch on your smart TVs and personal devices are all encoded with a lossy codec, which means taking the original file and reducing as much of the visual information as possible while still allowing the image to look great. All streaming video is encoded using lossy codecs.
There are many different video codecs available – including proprietary ones, algorithms that have been developed by a company and can only be played back on devices made by that company or by licensing its technology. More common are open-source or standards-based codecs. These are typically less expensive to use and don’t require content owners to be locked into a closed system. Today’s most popular standards-based codecs for video streaming are AVC/H.264 and HEVC/H.265. Broadcasters and pay TV operators sometimes still use MPEG-2, ALL STREAMINGVIDEO IS ENCODEDUSING LOSSY CODECS
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