VIDEOINFOHEADER2 Structure

Articolo
03/07/2008

Microsoft DirectShow 9.0

VIDEOINFOHEADER2 Structure

The VIDEOINFOHEADER2 structure describes the bitmap and color information for a video image, including interlace, copy protection, and pixel aspect ratio information.

Syntax

typedef struct tagVIDEOINFOHEADER2 {
    RECT                rcSource;
    RECT                rcTarget;
    DWORD               dwBitRate;
    DWORD               dwBitErrorRate;
    REFERENCE_TIME      AvgTimePerFrame;
    DWORD               dwInterlaceFlags;
    DWORD               dwCopyProtectFlags;
    DWORD               dwPictAspectRatioX; 
    DWORD               dwPictAspectRatioY; 
    union {
        DWORD           dwControlFlags;
        DWORD           dwReserved1;
    };
    DWORD               dwReserved2;
    BITMAPINFOHEADER    bmiHeader;
} VIDEOINFOHEADER2;

Members

rcSource

RECT structure that specifies what part of the source stream should be used to fill the destination buffer. Renderers can use this field to ask the decoders to stretch or clip. For more information, see Source and Target Rectangles in Video Renderers

rcTarget

RECT structure that specifies that specifies what part of the destination buffer should be used

dwBitRate

Approximate data rate of the video stream, in bits per second.

dwBitErrorRate

Data error rate of the video stream, in bits per second.

AvgTimePerFrame

The video frame's average display time, in 100-nanosecond units. For more information, see the Remarks section for the VIDEOINFOHEADER structure.

dwInterlaceFlags

Flags that specify how the video is interlaced. This member is a bit-wise combination of zero or more of the following flags. The flags in Group 2 are mutually exclusive, and so are the flags in Group 3. (The flags in Group 2 are not recommended.) The flags in Group 1 may be combined with each other, and with one flag each from Group 2 and Group 3. See the table at the bottom of this page for more information about flag combinations.

Flag	Description
Group 1
AMINTERLACE_IsInterlaced	The stream is interlaced. If this flag is absent, the video is progressive and the other bits are irrelevant.
AMINTERLACE_1FieldPerSample	Each media sample contains one field. If this flag is absent, each media sample contains two fields.
AMINTERLACE_Field1First	Field 1 is first. If this flag is absent, field 2 is first. (The top field in PAL is field 1, and the top field in NTSC is field 2.)
Group 2
AMINTERLACE_FieldPatField1Only	The stream never contains a field 2.
AMINTERLACE_FieldPatField2Only	The stream never contains a field 1.
AMINTERLACE_FieldPatBothRegular	There is one field 2 for every field 1.
AMINTERLACE_FieldPatBothIrregular	The stream contains an irregular pattern of field 1 and field 2.
Group 3
AMINTERLACE_DisplayModeBobOnly	Bob display mode only.
AMINTERLACE_DisplayModeWeaveOnly	Weave display mode only.
AMINTERLACE_DisplayModeBobOrWeave	Either bob or weave mode.

Set undefined flags to zero, or the connection will be rejected.

dwCopyProtectFlags

Flag set with the AMCOPYPROTECT_RestrictDuplication value (0x00000001) to indicate that the duplication of the stream should be restricted. If undefined, specify zero or else the connection will be rejected.

dwPictAspectRatioX

The X dimension of picture aspect ratio. For example, 16 for a 16-inch x 9-inch display.

dwPictAspectRatioY

The Y dimension of picture aspect ratio. For example, 9 for a 16-inch x 9-inch display.

dwControlFlags, dwReserved1

This field was originally named dwReserved, and was required to be zero. The field was renamed to dwControlFlags, and must contain a bitwise OR of zero or more of the following flags:

Value	Description
AMCONTROL_USED	Indicates the dwControlFlags flags are used.
AMCONTROL_PAD_TO_4x3	The image should be padded and displayed in a 4 x 3 area.
AMCONTROL_PAD_TO_16x9	The image should be padded and displayed in a 16 x 9 area.
AMCONTROL_COLORINFO_PRESENT	Additional color information is contained in the upper 24 bits of the dwControlFlags field.

The AMCONTROL_USED flag provides backward compatibility with older filters. If the AMCONTROL_USED flag is not set, the remaining bits in this field should be ignored. If a filter uses any of the other flags, it should set the AMCONTROL_USED flag.

The two AMCONTROL_PAD_xxx flags are used by decoders to determine the aspect ratio of the output rectangle. The source filter sets the AMCONTROL_USED flag and one of the padding flags and calls QueryAccept on the downstream pin. If the decoder rejects the type, the source filter should set the dwControlFlags field to zero. For more information on the use of these flags, see MPEG Decoder Preprocessing Transformations.

If the AMCONTROL_COLORINFO_PRESENT flag is set, it means the upper 24 bits of the dwControlFlags field are treated as a DXVA_ExtendedFormat structure. See Remarks for more information.

If this field contains any combination of flags that the filter does not support, the filter should reject the media type.

dwReserved2

Reserved for future use. Must be zero.

bmiHeader

BITMAPINFOHEADER structure that contains color and dimension information for the video image bitmap.

When used inside a VIDEOINFOHEADER2 structure, the semantics of the BITMAPINFOHEADER structure differ slightly from how the structure is used in GDI. For more information, refer to the topic BITMAPINFOHEADER Structure.

Remarks

The dwInterlaceFlags field indicates whether the video is interlaced, and if so, the format of the fields within the media samples. The following table shows the valid interlace modes for the Overlay Mixer and Video Mixing Renderer filters.

Display Mode	Interlace Flags	Description
Progressive frames	None	The video stream is not interlaced.
Non-interleaved bob	AMINTERLACE_IsInterlaced \| AMINTERLACE_1FieldPerSample \| AMINTERLACE_DisplayModeBobOnly	The entire video stream is interlaced, and each media sample contains a single video field.
Interleaved bob	AMINTERLACE_IsInterlaced \| AMINTERLACE_DisplayModeBobOnly	The entire video stream is interlaced. Each media sample contains two video fields. Flags on the media sample indicate which field to display first.
Weave	AMINTERLACE_IsInterlaced \| AMINTERLACE_FieldPatBothRegular \| AMINTERLACE_DisplayModeWeaveOnly	The video stream is interlaced, and each sample contains two video fields. The fields should not be deinterlaced.
Bob or weave	AMINTERLACE_IsInterlaced \| AMINTERLACE_DisplayModeBobOrWeave	The video stream varies between progressive and interlaced content. Each media sample contains either a progressive frame or two video fields. Flags on the media sample indicate the correct way to display the contents.

If the video is interlaced, the media samples may carry flags that describe the contents of the sample (such as field 1 or field 2), along with the rendering requirements. These are specified by setting the dwTypeSpecificFlags member of each media sample's AM_SAMPLE2_PROPERTIES structure. The following table shows the valid media sample flags for each of the display modes listed in the previous table. To set these flags, call IMediaSample2::SetProperties on the media sample.

Display Mode		Media Sample Properties
Progressive frames		None
Non-interleaved bob		AM_VIDEO_FLAG_FIELD1 or AM_VIDEO_FLAG_FIELD2
Interleaved bob	Field 1 first	AM_VIDEO_FLAG_FIELD1FIRST
Interleaved bob	Field 2 First	None
Weave		AM_VIDEO_FLAG_WEAVE
Bob or weave	Bob, field 1 first	AM_VIDEO_FLAG_FIELD1FIRST
	Bob, field 2 first	None
	Weave	AM_VIDEO_FLAG_WEAVE

Use the bit mask AMINTERLACE_FieldPatternMask to check the field pattern flags in dwInterlaceFlags:

switch (dwInterlaceFlags & AMINTERLACE_FieldPatternMask)
{
case AMINTERLACE_FieldPatField1Only:
    // Stream never contains a Field 2.

case AMINTERLACE_FieldPatField2Only:
    // Stream never contains a Field 1.

case AMINTERLACE_FieldPatBothRegular:
    // One Field 2 for every Field 1.

case AMINTERLACE_FieldPatBothIrregular:
    // Random pattern of Field 1 and Field 2.
}

Use the bit mask AMINTERLACE_DisplayModeMask to check the display mode flags in dwInterlaceFlags:

switch (dwInterlaceFlags & AMINTERLACE_DisplayModeMask)
{
case AMINTERLACE_DisplayModeBobOnly:
    // Bob display mode only.

case AMINTERLACE_DisplayModeWeaveOnly:
    // Weave display mode only.

case AMINTERLACE_DisplayModeBobOrWeave:
    // Either bob or weave mode.
}

Interlaced video samples must have valid time stamps. Otherwise, it is not guaranteed that the display driver can deinterlace the video. If you need to display an interlaced video frame with no time stamp, set the AM_VIDEO_FLAG_WEAVE flag on the sample as follows:

IMediaSample2* pSample2 = NULL;
hr = pSample->QueryInterface(IID_IMediaSample2, (void**)&pSample2);
if (SUCCEEDED(hr))
{
    AM_SAMPLE2_PROPERTIES Prop;
    hr = pSample2->GetProperties(sizeof(Prop), (BYTE*)&Prop);
    if (SUCCEEDED(hr))
    {
        Prop.dwTypeSpecificFlags = AM_VIDEO_FLAG_WEAVE;
        hr = pSample2->SetProperties(sizeof(Prop), (BYTE*)&Prop);
    }
    pSample2->Release();
}

This causes the driver to display the two fields as one frame, using weave mode, without deinterlacing.

Extended Color Information

If the AMCONTROL_COLORINFO_PRESENT flag is set in the dwControlFlags member, you can cast the dwControlFlags value to a DXVA_ExtendedFormat structure to access the extended color information, as shown in the following code.

VIDEOINFOHEADER2 *pVIH2;
DXVA_ExtendedFormat& flags = (DXVA_ExtendedFormat&)pVIH2->dwControlFlags;

Ignore the SampleFormat member of the DXVA_ExtendedFormat structure, because it corresponds to the lower 8 bits of dwControlFlags, which are reserved for the AMCONTROL_xxx flags. The DXVA_ExtendedFormat structure is documented in the Windows DDK documentation.

Requirements

Header: Dvdmedia.h.

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VIDEOINFOHEADER2 Structure

VIDEOINFOHEADER2 Structure

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