transcoding

Transcoding is the reformatting of messages encoded in a particular encoding into a message with a different encoding that can be interpreted by a different receiving station. Transcoding techniques are used wherever encoded signals are incompatible with each other, such as in multimediamessaging services( MMS), where sending and receiving terminals often have different image formats. Transcoding reformats such signals into a more suitable format.

Transcoding reformats the data format of one signal into that of another, without going through the process of decoding and subsequent encoding. Such transcoding is possible as long as the codecs of the signal source and the signal sink are similar. If this is not the case, the transcoding works with an intermediate format with which the ordinary signal content is not affected. From the intermediate format the final format is encoded by means of coding.

Transcoding refers not only to file formats for audio, video, graphics or others, but also to software, programs, image formats, screen resolutions, aspect ratios or transmission speeds. In the case of image transcoding, this is also referred to as image scaling or transsizing. This transsizing is used, for example, in the transfer of cell phone displays to another display size or to a digital picture frame. In data rate conversion, transrating, the data rate of one encoding is transcoded to that of another. Transrating is used, for example, in the transcoding of voice coding in GSM networks from 13 kbit/s to the data rate of ISDN at 64 kbit/s in Transcoding Equipment( TCE).