Sony will begin offering a software update for its PSX digital video recorder and game console on Wednesday that will add almost all of the features originally promised by the company but missing from the device when it went on sale in Japan in December.

Users with a broadband connection to their PSX units will be able to download the new software while others will be able to order a CD-ROM containing the new software from Sony.

The PSX, which combines the functions of a hard-disk drive and DVD-based video recorder with a PlayStation 2 games console, went on sale in Japan in December as one of the key products of Sony's year-end range. It was, however, missing a number of features originally promised by Sony when the company first showed the device at a local trade show two months earlier.

Several promised functions were absent, such as support for DVD+RW discs and the ability to play back data CD-R discs (although audio CDs recorded on CD-R discs were supported), display TIFF and GIF format images, show movies taken with Sony's Cybershot digital still cameras and play back MP3 files. Copying video files from the PSX's hard disk drive to DVD discs was at 12X speeds rather than the promised 24X, and it also could not connect to the PlayStation BB online gaming service.

Sony was unable to deliver the functions because it had run out of time in developing the product to meet the December sales target, the company said.

The new software update adds not only these functions but also several new features such as playback of commercial DVDs at 30X speeds and the ability to record both audio channels of a bilingual television broadcast. However, one feature is still missing from the device – the ability to connect to PlayStation BB. This feature will be available in a further update, a company spokesman said.

The PSX is one of the first of a new generation of electronics devices that can have features added through software updates after the devices have gone on sale. This week, Sony will also provide an update for owners of its Blu-ray Disc video recorder that adds support for digital terrestrial television. Earlier this year Toshiba offered owners of several of its LCD (liquid crystal display) televisions a new software package that added a Web browser function to the television.