US Patent 7227888 Testing loops for channel codecs

A method for measuring the performance of decoding in a telecommunication system comprising a decoder and a testing apparatus for supplying test data to the decoder. A test data comprising channel coded speech parameters and an inband data field in a frame format is generated in the testing apparatus and transmitted to the decoder for decoding. The decoder extracts at least a part of the inband data field from the decoded test data and transmits at least the part of the inband data field back to the testing apparatus. The performance of decoding is measured by comparing the transmitted inband data field and the received inband data field in the test apparatus.