The present invention relates to converting media bitstreams across different networks in a media gateway without any algorithmic delay, and reduces the computation load within the transmission in the situation where the bandwidth of the outgoing network varies dynamically. A first embodiment of the present invention provides an apparatus and a method for a Reduced-Algorithmic-Delay Media Stream Unit Conversion module which is a light weight Simple Pass-Through operation. A second embodiment of the present invention provides an apparatus and a method for a Reduced-Algorithmic-Delay Video Rate Conversion. An alternative embodiment provides an apparatus and a method for a Smart Pass-Through Operation which involves switching between the Simple Pass-Through and the Rate Converter. The methods and apparatuses provided by the first and second embodiment can be used as a stand alone system, or as part of the module of the alternative embodiment.