## MMPM/2 Device Driver Reference

[prev][next][parent][TOC]

### Playback

Video playback is all done through the VCAI_PLAY IOCtl interface. Unlike record, this is performed through the Inter-Device Driver (IDC) DDCMD messages. The MMPM/2 subsystem invokes the VCAI_PLAY functions from one of two places:

For compressed playback, the hardware (COmpressor/DECompressor) CODEC calls the play function directly with the compressed data.

With compressed data playback, the MCD issues all the VSD/PDD commands except the VCAI_PLAY and VCAI_LOAD_MICROCODE commands-which are issued by the CODEC.

In the case of uncompressed playback, the play function is issued by the Direct Interface Video Extensions (DIVE) component after the appropriate CODEC has decompressed the image. DIVE knows to call this video device driver instead of the normal display driver because of the [ OverlayAccelerator] entry in the DIVE.INI file, where the VSD DLL (VSDDRIVE =) and video device driver (PDDNAME=) names are specified for DIVE. When DIVE uses the VSD/PDD to play back video, the MCD is unaware of the hardware; DIVE issues all of the VSD/PDD commands to control window placement and playback function.