Make your own free website on Tripod.com
VHD DiscWorld
AHD: Audio/Advanced High Density

Home

The VHD Video Disc System | 3D Compatible Video | 1982 SMPTE Journal Article | VHD in America Part 2 | VHD News Clippings | Inside The VHD Disc System | Video Review Magazine's VHD Report | GE VHD Player Test (August 1981) | VHD In The U.K. | Dual-Standard NTSC/PAL/SECAM VHD | Review: Victor HD-7900 VHD Player | Review: Victor HD-9300 3D VHD Player | Comparing VHD/LD/CED | AHD: Audio/Advanced High Density

4-Channel digital sound, still pictures and advanced computer control

AHD with still images and 3 channels of digital sound

In addition to standard video and analog stereo audio, Victor designed the VHD format as a 4-channel digital audio disc format called AHD (Audio High Density). AHD could carry up to 4 discrete channels of 16-bit audio, or could use any one of the channels to carry still digital images with the remaining channels used for audio. Most documents from Victor show 3 channels with a still-picture stream. AHD was accepted as a "standard" by the DAD group, along with the Compact Disc, but the CD formats success discouraged Victor from introducing the AHD format. Victor then changed the meaning of the AHD designation to Advanced High Density, meaning interactive computer control. Thanks to the VHDpc port on most VHD players, the VHD player could be connected to an external computer (MSX in Japan) and various interactive functions could be carried out. Many anime games were released on VHD/AHD. Victor used the VHD stylus' 'kick' ability to store different 'branches' of programs on adjacent tracks, thus enabling rapid switching and searching among points on the disc. The interactive VHD/AHD game discs (along with the MSX interfaces) are still very popular and command high prices on the used Japanese market.