What transcoding is
Transcoding is an umbrella term referring to several different digital media tasks (subsets). Transcoding at its basic definition is to decompress/decode digitized media content, altering it in some way and then recompress it using either transcoding software, hardware, or transcoding in the cloud. Video transcoding could for example consist of changing the audio or video format (codec). Video transcoding may also include performing simpler tasks such as adding watermarks, logos or graphics to a video. Transcoding might also include the two types of changes below:
- Transrating refers to the act of changing bitrates of a video or live stream, for example converting a 4K video input stream at 13 Mbps into a lower-bitrate stream (called renditions).
- Transsizing is exactly as it sounds, it refers to resizing a video frame to a different resolution to fit different websites, video players and similar from for example a resolution of 3840×2160 (4K UHD) down to 1920×1080 (1080p) or 1280×720 (720p).
When someone mentions “stream or video transcoding”, they may be referring to any combination or all of the above mentioned tasks. All of them are available in Vidispines’ cloud video transcoding service VidiNet.
What transcoding isn't
Video transcoding is not to be confused with the term transmuxing (also available through VidiNet), which can be described as the process of repackaging, packetizing or rewrapping. While transcoding refers to actually changing or altering a file in one way or another, transmuxing simply takes a compressed audio or video file and repackages it into a different format without changing the codec. Transmuxing requires a lot less process power than transcoding since it does not involve any alterations.
It’s a great feature when you want to be able to repackage something without changing the content of the file. As there is no digital generation, the quality of the file will also stay intact.
Transmuxing example: Let’s say you have some H.264/AAC content. By transmuxing and changing the container it’s packaged in, you will be able to deliver it as HTTP Live Streaming (HLS), Smooth Streaming, HTTP Dynamic Streaming (HD) or Dynamic Adaptive Streaming over HTTP (DASH).