In telecommunication, transcoding is the direct digital-to-digital conversion from one encoding scheme, such as voice LPC-10, to a different encoding scheme without returning the signals to analog form.

Encoding into a lossy compression format will strip details from the file. Transcoding from one lossy compression format to another will compound the loss of details from the file. (eg: transcoding a sound file from OGG Vorbis to MP3). The preferred method is to save all audio "masters" in a lossless audio format such as FLAC or WavPack, and then transcode directly from the lossless source file to your preferred lossy format such as MP3. This procedure preserves as much of the original audio signal as possible and prevents compound loss of details from the file.

Note: The transcoded signals, i.e., the digital representations of analog signals may be any digital representation of any analog signal, such as voice, facsimile, or quasi-analog signals.

Source: From Federal Standard 1037C and from MIL-STD-188