Abstract. The transmission of coded video signals is perceptually favoured to provide, to the receiving end, a constant quality with respect to time. In the block type of video coder like ITU H.263, maintaining a constant quality necessitates a certain amount of consistency in the quantisation process. The step-side quantisation parameter Qp remains unaltered all over the coding process time in order to offer a fixed rate distortion to the decoded sequence, the fact that is visuall perceived as a constant-quality scene. Due to the spatial and temporal redundancies of raw video signals, maintaining a fixe quantisation parameter leads to the bit rate variability of a encoded video stream. However, the bit rate variability characteristic of an encoded video signal can be considered as an inpediment for bit-error detection and correction when a video stream is transmitted over error-prone environments such mobile radio links, and high interference terrestrial links. The paper incorporates the discussion and implernentation of some algorithrns applied to ITU H.263 video coding algorithm to enhance its resilience to channel degradation and maintain its performance when its bit stream is transmitted over error-prone media. The resilience techniques are analysed and evaluate through objective and subjective measurements. Moreover high quality in-house vocoder for low bit rate applications is described and its error resilience issues are addressed.