An integrated cast and sling system capable of intermediating seamless multimedia data and playback transfers across multiple display devices is disclosed. The integrated cast and sling system contains a cast-sling box (CSB) connected to a conventional cable or satellite set-top box and a plurality of multimedia signal sources. In one instance, the CSB operates as an intermediary and specialized set-top box that provides seamless interoperability of multimedia cast or sling commands and related multimedia data and playback transfers between a gesture-based multimedia casting and slinging command device (e.g. a smart phone, a tablet computer, or another device with gesture command capabilities) and a targeted device (e.g. a television, a computer display, or an electronic device with a display unit). The CSB also provides intelligent transcoding or conversion of a sling or cast command from the gesture-based multimedia casting and slinging command device to ensure protocol compatibility with the targeted device.