Microsoft DirectX 8.1 (C++)

MPEG2_TRANSPORT_STRIDE

The MPEG2_TRANSPORT_STRIDE structure describes the format of multiplexed MPEG-2 packets otherwise called stride packets. This structure defines a stride packet and is used with AM_MEDIA_TYPE when the AM_MEDIA_TYPE.majortype is MEDIATYPE_Stream and the AM_MEDIA_TYPE.subtype is MEDIASUBTYPE_MPEG2_TRANSPORT_STRIDE.

Syntax

struct MPEG2_TRANSPORT_STRIDE {
    DWORD   dwOffset
    DWORD   dwPacketLength
    DWORD   dwStride
};

Members

dwOffset

Specifies the offset, in bytes, from the beginning of the packet to the first byte of the embedded MPEG-2 transport packet.

The valid values of dwOffset depend upon the value of AM_MEDIA_TYPE.pbformat.

Value of AM_MEDIA_TYPE.pbformat	Value of dwOffset
NULL	0
not NULL	Must range between zero and (dwStride - dwPacketLength) inclusive.

dwPacketLength

Specifies the length, in bytes, of the embedded MPEG-2 transport packet.

Currently, dwPacketLength is fixed at 188 bytes.

dwStride

Specifies the length, in bytes of the stride packet.

The valid values of dwStride depend upon the value of AM_MEDIA_TYPE.pbformat.

Value of AM_MEDIA_TYPE.pbformat	Value of dwOffset
NULL	188
not NULL	Must be >= dwPacketLength

Remarks

This media subtype provides capture devices the ability to avoid memory copies if transport packets, as defined in H.222.0, are not packed contiguously within a transport buffer.

Input buffers that carry multiplexed stride packets have these restrictions:

Stride packets must be packed contiguously within an input buffer.
The buffer must begin with an instance of MPEG_TRANSPORT_STRIDE.
No bytes may precede the first stride packet.
No bytes may follow the last byte of the last stride packet.

Input buffers have no restriction on the number of stride packets per buffer.