Comparison of some efficient techniques for transform coding of images with reduced blocking effects

Transform coding techniques for image transmission are examined in detail and compared to the DCT (discrete cosine transform) under the same conditions, e.g. data rate, type of quantization of coefficients, number of operations needed, suitability for real-time execution, and quality of the received image. The quality is measured by objective (normalized mean square error) and subjective criteria. The images used in the experiments represent different situations which may arise in practice (buildings, head and shoulder, aerial images). These investigations show that the LOT (lapped orthogonal transform) has some advantages at data rates about 0.5 b/pixel, although DCT is better regarding computing speed and ringing effects