Abstract: A method and apparatus for testing the functionality of a data decoder is provided. The functionality of a decoder is examined through the used of a functional bitstream. The functional bitstream is a bitstream which when decoded by a properly functioning decoder, produces a desired output. Such a bitstream can be created by receiving an input bitstream, compressing the input bitstream, thereby creating a compressed input bitstream. The compressed input bitstream is then decompressing, thereby creating an intermediate bitstream. The intermediate bitstream is then compressed, thereby creating a compressed intermediate bitstream. The compressed intermediate bitstream is then decompressed, thereby creating an output bitstream. Finally, a comparison is performed to determine if the output bitstream is equivalent to a desired bitstream.

Abstract: A method and apparatus for producing a variable bit rate audio signal is disclosed. An audio signal is encoded into a plurality of encoded audio signals at different bit rates. A variable bit rate audio signal is produced by selecting between the plurality of encoded audio frames of different bit rates in accordance with a selection criterion.