Research of DSC using the ISO/IEC 29170 interleaved protocol, in which an uncompressed reference image is presented side by side with a rapidly alternating sequence of the compressed test image and uncompressed reference image, and performed with various types of images (such as people, natural and man-made scenery, text, and known challenging imagery) shows that although in many (sometimes most) cases DSC satisfied the standard's criterion for visually lossless performance, in many trials participants were nonetheless able to detect the presence of compression.