Encoding and decoding are two opposite processes. Encoding is done with the intension of increasing the usability of data in different systems and to reduce the space required for storage, while decoding converts encoded information back in to its original format. Encoding is done using publicly available methods and it can be easily reversed (decoded). For example, ASCII encoding is just a mapping between characters and numbers. So decoding it is straight forward. But decoding messages sent via a noisy channels will not be straight forward, because the message could be tampered with noise. In such instances decoding involves complex methods that are used to filter out the effect of noise in the message.
There are two types of video encoding; live and file-based, and it’s important to make the distinction between them. Live video encoding is the process of compressing large, raw video and audio files so that they use less network bandwidth. When it comes to transporting uncompressed raw video, this can mean a colossal amount of data to send over any connection. Given the constant struggle for bandwidth efficiency, compression significantly reduces the bandwidth required, making it possible for real-time video streams or files to be easily transmitted across constrained networks such as the public internet.
When working with video files rather than live video, encoders are used to compress and reduce the size of video content so that it can take up less storage space and be easier to transfer from one part of a video production workflow to another.
Essentially the opposite of live encoding, video decoding is the process of decoding or uncompressing encoded video in real-time. A video decoder converts an encoded video stream to HDMI for display on a screen or to SDI for connected to broadcast production systems including video production switchers. Video decoders can also decode embedded audio tracks for sound production as well as metadata for information on video formatting, time codes, subtitles, and closed captioning. For non-broadcast applications such as ISR, metadata may also include vital KLV information.
Some video decoders are able to support multiple incoming streams and include the ability to resync them prior to decoding to SDI.