1. A method for producing a destination codec bitstream in a destination codec from a source codec bitstream in a source codec, by a transcoder comprising a processor, the method comprising: determining if a pass through is to be performed; if the pass through is to be performed, outputting the source codec bitstream as the destination codec bitstream; if the pass through is not to be performed, outputting the destination codec bitstream in the destination codec, wherein outputting the destination codec bitstream comprises: determining if a linear prediction analysis is to be performed; and determining if an analysis-by-synthesis search for one or more excitation parameters is to be performed.