Before the HD DVD and Blu-ray formats hit the market, there was a third high definition format called D-Theater that was released back in 2002 in the USA only. D-Theater is a D-VHS cassette which could provide content in both 720p and 1080i along with a Dolby Digital audio track. D-VHS tapes could store between 25GB and 50GB of data storage depending on the tape length, closely matching the capacity of Blu-ray discs. The tape itself looks almost identical to a VHS tape.
Like the Blu-ray format, the D-VHS format was region controlled for pre-recorded content - Region 1 for the USA, region 2 for Japan and Region 3 for South Korea, although pre-recorded content was only released in the USA. The studios that released titles on the format include 20th Century Fox, Atrisan Entertainment, DreamWorks and Universal Studios. Some Japanese units could be hacked to play USA region D-Theater tapes.
Although the first Blu-ray and HD DVD titles did not reach the market until 2006, the last title released on the D-Theater D-VHS format was 20th Century Fox's I, Robot released late 2004, making it one of the shortest physical video formats in history. This was likely due to the rapid take up of the DVD format and that most consumers did not have a high definition television at the time.
Going by Techmoan's video below, D-Theater had a pretty interesting way of enforcing copy protection. D-Theater D-VHS recorders could only record in high definition from its FireWire input port where the bit-stream did not have a copyright flat set. They could only record in standard definition from its composite analogue inputs as the high definition output was over component video and HDMI in the later models. Some of these later machines could also play additional sound tracks including DTS.
The following video by Techmoan gives a nice demonstration of a D-Theater unit, including loading the tape and the internals of a player:
