A cart has a base for securely receiving one or a plurality of stacked containers, such as drywall compound, paint or other dense material, allowing a user to work from an open container while the container is on the cart. Media hardware, such as a display controller, may play media. The system comprises an imaging device for acquiring the image data and an image processing device coupled to the imaging device. The retaining portion defines a pair of wings bending upwards from two side edges thereof and projecting out of the receiving groove, and the base portion defines corresponding pressing portions projecting to and pressing the wings. Each code block is partitioned into multiple subblocks, and each data packet in each code block is inner encoded and modulated to generate modulation symbols for the packet.