Transcoding is the process of converting one digital format to another, or re-encoding a digital file in order to change one or more parameters. There are several broad definitions of the term, including:
- Converting a file to a different format, e.g. from Windows Media to Quicktime. This is often done in order to provide different options for end users, especially on websites.
- Re-encoding a file in the same format. You might want to do this, for example, to lower the bitrate for distribution on the web or mobile devices.
- In the world of software development, transcoding can refer to the process of recompiling an application to work on a different platform or operating system.
Transcoding is usually achieved by using a specialist application which simulates playback using the file's original codec, while simultaneously re-encoding it using a different codec.
Transcoding is almost always a lossy process, i.e. image quality is compromised by data loss. This effect is cumulative — transcoding a file that has already been transcoded results in double quality loss. For this reason it is best to keep a master copy (preferably uncompressed) and use this as the source file to transcode into all the different required formats.