Efficient fast intra mode decision using transform coefficients

The H.264/AVC standard substantially improved its coding efficiency and subjective quality by using the intra prediction technique and the adaptive coding between inter and intra modes based on rate-distortion optimization. This encoding scheme, however, increases encoding complexity dramatically and causes troubles in its practical applications in the real-time mobile environment. In order to decrease the complexity, various methods are proposed but most of them take only its current block into consideration for selecting candidate intra modes, which naturally causes degradation in PSNR (Peak Signal to Noise Ratio) and bitrate. The proposed fast intra mode decision finds the candidate modes by analyzing transformed coefficients of neighboring blocks as well. We verify this proposed scheme reduces encoding complexity without noticeable degradation of PSNR and bitrate.