In this paper, we present an intra-fame rate control algorithm for ultra low delay H.264/AVC coding. In real time video coding, all the macro-blocks within a current frame may be unavailable before encoding them. Hence the proposed scheme predicts relative complexity of the current block from complexity of available macro-blocks within previous and current frames. Then, the algorithm allocates bits to each macro-block considering the relative complexity between the macro-block and the current frame. Quantization parameter of each macro-block is obtained by comparing the generated and allocated bits and is refined for improving coding performance. The required buffer size is only around one-third of average bits required for encoding a single frame. Simulation results show that the proposed algorithm can prevent the buffer from overflow and underflow while it provides better coding performance.