IEEE 1394 AV/C VCR Subunit Driver Development Concepts (Windows CE 5.0)
Interfaces and technologies associated with IEEE 1394 have specific standards documents associated with them.
It is impractical to attempt to present information on each of the technologies here. Microsoft recommends you obtain the specific standards, so you can understand the details of the technologies involved.
The standard that relates most to IEEE 1394 AV/C VCR subunit drivers is the AV/C Digital Interface Command Set VCR Subunit Specification Version 2.0.1, made publicly available by the 1394 Trade Association.
However, there are cases where the information in the previously mentioned specification is superseded by the IEEE 1394 AV/C VCR subunit driver documentation.
For example, BCD values are automatically converted for the user to and from decimal by the VCR subunit driver; the previously mentioned specification refers to many fields as BCD encoded.
Each of these instances is generally well documented, but you should keep yourself informed about the differences between the VCR subunit driver documentation and the previously mentioned specification.
The VCR subunit driver is intended to provide applications with the ability to control devices on the IEEE 1394 bus that export an AV/C tape subunit API. It does not provide the capability of exporting VCR-style functionality. That task requires a virtual subunit driver.
The VCR subunit driver is designed to include the IEEE 1394 streaming filter driver (AVC_STREAM) hierarchically below it in the device stack. For more information, see IEEE 1394 Streaming Filter Drivers.
The VCR subunit driver handles control of the VCR device, and the IEEE 1394 streaming filter driver provides streaming functionality. Commands not recognized by the VCR subunit driver are merely passed down to the IEEE 1394 streaming filter driver, so the actual set of applicable commands include those for both drivers.
IEEE 1394 AV/C VCR Subunit Driver Control Functionality
The AV/C Digital Interface Command Set VCR Subunit Specification Version 2.0.1 combines commands suitable for both consumer and professional VCR products into a single document.
The professional commands are significantly more complex than the consumer commands and are heavily associated with detailed editing functionality.
TVPAK is designed for use in consumer products and therefore has little need for the type of functionality provided by the professional commands. As such, the command set supported is a subset of command set documented in the specification. This subset includes those commands that are most likely to be implemented on a consumer VCR.
IEEE 1394 AV/C VCR Subunit Driver APIs
The API descriptions are divided into two categories: the IOCTLs themselves and a detailed list of commands that can be performed with IOCTL_VCR_AVCCMD. The IOCTLs are direct calls to DeviceIoControl that you can make. IOCTL_VCR_AVCCMD has so many variations that the commands are documented separately.
The following illustration shows where AV/C is in the IEEE 1394 stack.
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