Improved H.264-based video coding using an adaptive transform

In block-based video coding, the Discrete Cosine Transform (DCT) has been adopted for signal decorrelation in state-of-the-art standards. Although the Karhunen Loeve Transform (KLT) is known to achieve optimal energy compaction, it has been reported to offer only moderate compression as the KLT basis functions are source dependent and hence require the transform itself to be coded. This paper describes a technique for prediction-error block coding using the KLT. The proposed method does not require coding of the KLT bases. Instead the basis functions can be derived at the decoder in a manner similar to the encoder. The proposed method is incorporated into a standard H.264 video codec using an adaptive transform selection approach. Our experiments show that the Peak Signal-to-Noise Ratio (PSNR) improvement of up to 0.9 dB is achieved with the proposed technique when compared with the standard H.264 codec.