source ue 1202 the sound may be represented by digital data such as pcm the codec runs in encoder mode to produce voip packets that are presented to the source ran simulation 720 which is chained to the target ran simulation 730 these simulations delay the voip packets before they are transmitted over the air interface to the real dut ue 4 the dut ue 4 uses the codec in decoder mode to obtain first a digital representation of the sound such as pcm the dut ue 4 may then use a digital to analog converter dac to produce analog sound the resulting sound that represents the stream of packets is captured at the audio video port of the server pc 1500 digitized and stored as a degraded media file 11 pesq or polqa or a similar procedure can finally be used to compare and analyze the reference and degraded files to obtain the mos there are alternative ways to produce the degraded file 11 for evaluation in one alternative the digital result of the ue 4 39 s decoder is a stream of packets that is captured by the ue 4 in an internal degraded file that degraded file can later be captured from the ue 4 by the server pc 1500 for example over the air interface or over the ue 4 39 s universal serial bus usb interface in another alternative the decoder 39 s digital output is streamed out of an interface of the ue 4 e g usb and captured externally on another computer or.