Compartilhar via

DVINFO Field Settings in the MSDV Driver

  • Artigo
 
Microsoft DirectShow 9.0

DVINFO Field Settings in the MSDV Driver

This section describes how the MSDV driver fills in the DVINFO structure.

The DVINFO structure defines the format block for pin connections between MSDV and other filters. By default, the DV Splitter filter is used when capturing from a DV device, and the DV Mux filter is used when transmitting to the device. However, applications may provide their own custom filters, so it is useful to understand how MSDV populates the DVINFO format block.

The DVINFO structure contains the following information:

  • Two audio auxiliary (AAUX) source packs, for the first and second audio blocks.
  • Two AAUX source control packs, for the first and second audio blocks.
  • A video auxiliary (VAUX) source pack.
  • A VAUX source control pack.

Every frame in a DV stream contains AAUX and VAUX packs. However, the DVINFO format block is static, and is only used to establish the pin connection. When the MSDV driver connects, it does not examine any of the AAUX or VAUX packs in the stream. Instead, it uses a set of default values, based on the following characteristics of the DV device:

  • Whether the device supports a consumer format (DVCR) or professional format (DVCPRO)
  • The signal type
  • Whether the format is NTSC or PAL. (If the device does not report this information, MSDV defaults to the NTSC settings)

Once streaming begins, it is the responsibility of the user-mode filters, such as the DV Splitter, to examine the actual contents of each DV frame. Because the information can change from frame to frame, the filter may need to perform a dynamic format change. For example, if the audio rate changes, the filter might need to renegotiate the audio type.

If you capture a type-1 DV file, the DVINFO structure is written into the file as the stream format ('strf') chunk. This data is taken directly from the format block provided by MSDV. As noted, the actual content of the stream might be different. It is the application's responsibility to examine the AAUX and VAUX packs in each frame.

In the following topics, you can find tables listing all of the fields used by MSDV.

When reading these tables, please consult the following specifications:

  • IEC 61834
  • SMPTE 314M
  • SMPTE 370

In each table, the first column gives the field code, followed by the number of bits (in parentheses). The remaining columns give the field values. Many of the AAUX and VAUX fields are not relevant for the pin connection, in which case MSDV sets a dummy value. The numeric value of the entire pack is listed at the bottom of each table. 

The notes after each table give more information about selected fields. For complete descriptions, refer to the specifications. Also, some fields do not have the same meaning in SMPTE 314M/SMPTE 370 as they do in IEC 61834. 

  • Note  Currently, DirectShow does not support DVCPRO formats. The values listed for the DVCPRO formats are defined for future use.

See Also