Data Range Intersections in AVStream

A data format is a single set of parameters describing some aspect of a connection. For example, an audio data format might specify a certain format of audio at X samples per second and Y bits per sample.

A data range specifies a sequence of valid parameters. For instance, an audio data range could specify a certain format of audio at A-B samples per second and C-D bits per sample.

The minidriver provides a list of data ranges that it supports for a specific pin in the DataRanges member of the corresponding KSPIN_DESCRIPTOR structure.

In AVStream, minidrivers can supply their own data-range intersection handlers by providing a pointer to a minidriver-provided callback routine in the IntersectHandler member of a KSPIN_DESCRIPTOR_EX. To let AVStream intersect the ranges, set this member to NULL. See AVStrMiniIntersectHandlerEx to learn how to define the callback routine.

If a minidriver provides an intersect handler, when an intersection needs to be made, the minidriver receives two data ranges that match in major type, subformat, and specifier. In addition, the required attributes of the data ranges match.

If the ranges intersect and sufficient buffer space is provided in the Data parameter of the AVStrMiniIntersectHandlerEx callback routine, the intersection routine chooses a format in the intersection and returns it to the caller in the buffer pointed to by Data.

If the two data ranges do not intersect, the handler returns STATUS_NO_MATCH.

If the minidriver has specified an AVStrMiniPinSetDataFormat dispatch, then AVStream calls this dispatch to inform the minidriver that AVStream is setting a specific format on the pin. Provide a pointer to your AVStrMiniPinSetDataFormat callback routine in the SetDataFormat member of the KSPIN_DISPATCH structure. (Minidrivers that are clients of stream class receive SRB_SET_DATA_FORMAT instead of AVStrMiniPinSetDataFormat.)

The minidriver can refuse a proposed format by returning STATUS_NO_MATCH from AVStrMiniPinSetDataFormat.

In addition to the initial call to AVStrMiniPinSetDataFormat before the pin is created, your minidriver could receive a second AVStrMiniPinSetDataFormat call just before the pin transitions to RUN state. If your AVStream or stream class client is a video capture minidriver and you receive such a notification, this dispatch contains the actual surface parameters. If possible, the minidriver should not fail this second format change. Do not assume that a second dispatch call will occur.

The minidriver should capture data in whatever format was contained in the last successful AVStrMiniPinSetDataFormat dispatch.


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