Media Foundation——媒体类型（1）

Media Foundaton对象的属性和特性

 每一个对象上的数据，都可通过“属性（Attributes）”和“特性(Properties)”来设置、描述。属性和特性相似但不同。

 

在Media Foundation中使用属性（Attributes）

属性（Attributes）= key +value

Key

是个GUID

Value

是个变量。变量的类型局限于：

ü         UInt32

ü         UInt64

ü         64-bit浮点数

ü         GUID

ü         以NULL结尾的宽字符类型（wide-character）字符串

ü         字节数组

ü         IUnknown指针

以上类型被包含在MF_ATTRIBUTE_TYPE枚举类型中：

typedef enum _MF_ATTRIBUTE_TYPE {

  MF_ATTRIBUTE_UINT32     = VT_UI4,

  MF_ATTRIBUTE_UINT64     = VT_UI8,

  MF_ATTRIBUTE_DOUBLE     = VT_R8,

  MF_ATTRIBUTE_GUID       = VT_CLSID,

  MF_ATTRIBUTE_STRING     = VT_LPWSTR,

  MF_ATTRIBUTE_BLOB       = VT_VECTOR | VT_UI1,

  MF_ATTRIBUTE_IUNKNOWN   = VT_UNKNOWN 

} MF_ATTRIBUTE_TYPE;

 

属性（Attributes）的说明

通过IMFAttributes接口定义属性组，这个接口是类型安全的。例如，设置32位的整形，可调用：IMFAttributes::SetUINT32。

属性（Attributes）中的key是唯一的，如果设置了两个相同key的属性（Attributes），则只有后一个有效。

通常IMFAttributes类型的指针会作为应用程序中某函数的参数，应用程序负责创建属性集，创建一个空属性集可用MFCreateAttribute。

HRESULT MFCreateAttributes(

  __out  IMFAttributes **ppMFAttributes,

  __in   UINT32 cInitialSize //存储的属性的初始元素数

);

 

举例

例子一

创建一个新属性集（Attributes），属性集名字为MY_ATTRIBUTE

extern const GUID MY_ATTRIBUTE;

HRESULT ShowCreateAttributeStore(IMFAttributes **ppAttributes)

{

    IMFAttributes *pAttributes = NULL;

    const UINT32 cElements = 10;  // 初始为10个元素

    // Create the empty attribute store.

    HRESULT hr = MFCreateAttributes(&pAttributes, cElements);

    //给key为MY_ATTRIBUTE的属性设置value.，value是字符串类型

    if (SUCCEEDED(hr))

    {

        hr = pAttributes->SetString(

            MY_ATTRIBUTE,

            L"This is a string value"

            );

    }

    // Return the IMFAttributes pointer to the caller.

    if (SUCCEEDED(hr))

    {

        *ppAttributes = pAttributes;

        (*ppAttributes)->AddRef();//注意：增加引用

    }

    SAFE_RELEASE(pAttributes);

    return hr;

}

 

例子二

获取设置的属性的value

HRESULT ShowGetAttributes()

{

    IMFAttributes *pAttributes = NULL;

    WCHAR *pwszValue = NULL;

    UINT32 cchLength = 0;

    // Create the attribute store.

    HRESULT hr = ShowCreateAttributeStore(&pAttributes);

    // Get the attribute.

    if (SUCCEEDED(hr))

    {

        hr = pAttributes->GetAllocatedString(

            MY_ATTRIBUTE,//key

            &pwszValue,//获取key对应的value,value是字符串类型

            &cchLength//获取key对应的value的长度

            );

    }

    CoTaskMemFree(pwszValue);

    SAFE_RELEASE(pAttributes);

    return hr;

}

 

 

属性序列化

可通过两种方式对存储的属性序列化：

ü         将属性集写入字节数组

ü         将属性集通过IStream写入流（Stream）

如果属性的value是IUnknown类型，即对应类型枚举值中的MF_ATTRIBUTE_IUNKNOWN，将不能被序列化。

Operation	Byte Array	IStream
Save	MFGetAttributesAsBlob	MFSerializeAttributesToStream
Load	MFInitAttributesFromBlob	MFDeserializeAttributesFromStream

 

HRESULT MFGetAttributesAsBlob(

  __in   IMFAttributes *pAttributes,

  __out  UINT8 *pBuf,//存储属性数据的数组

  __in   UINT cbBufSize//pBuf数组的字节长度

);

 

HRESULT MFSerializeAttributesToStream(

    IMFAttributes *pAttr,

    DWORD dwOptions,//如果被设置为MF_ATTRIBUTE_SERIALIZE_UNKNOWN_BYREF ,根据pstm的情况，决定如何序列化

    IStream *pStm//存储流的指针

);

 

 

 

 

在Media Foundation中使用特性（Properties）

一个特性也是一个key/value对。

Key是PROPERTYKEY结构体，该结构体由“GUID+DWORD型的值”组成

typedef struct {

    GUID fmtid;

    DWORD pid;//可设置从2往上的值，0、1被系统保留

} PROPERTYKEY;

 

设置和获取一个Media Foundation的对象的特性（Properties），要用到IPropertyStore接口。IPropertyStore接口中定义了一些方法：

Commit	Saves a property change.
GetAt	Gets a property key from an item's array of properties.
GetCount	Gets the number of properties attached to the file.
GetValue	Gets data for a specific property.
SetValue	Sets a new property value, or replaces or removes an existing value.

 

媒体类型（Media Type）

简介

媒体类型通过IMFMediaType接口描述，IMFMediaType继承自IMFAttribute，所以Media Type就是一些属性（Attribute）

IMFMediaType定义了的方法

Method	Description
FreeRepresentation	Frees memory that was allocated by the GetRepresentation method.
GetMajorType	Retrieves the major type of the format.
GetRepresentation	Retrieves an alternative representation of the media type.目前只能将Media Foundation中的media type转换为Directshow中的AM_MEDIA_TYPE
IsCompressedFormat	Queries whether the media type is a compressed format.
IsEqual	Compares two media types and determines whether they are identical.

 

优点

Directshow、DMO里面都有媒体类型，Media Foundation中的媒体类型相比它们有以下优点，优点源于Media Foundation的媒体类型是属性（Attribute）：

1.       可以省略那些不清楚的音视频参数。而Directshow、DMO的媒体类型的各个字段都必须被填写，而造成写错。

2.       扩展安全。以前的媒体类型都基于结构体（structure），如WAVEFORMATEXTENSIBLE是从WAVEFORMATEX扩展而来，指向结构体的指针指来指去就可能会造成异常发生。

 

MFCreateMediaType用于创建媒体类型（Media Type）。

 

媒体类型及子类型

主类型

GUID	Description
MFMediaType_Audio	Audio.
MFMediaType_Video	Video.
MFMediaType_Protected	Protected media.
MFMediaType_SAMI	Synchronized Accessible Media Interchange (SAMI) captions.
MFMediaType_Script	Script stream.
MFMediaType_Image	Image stream.
MFMediaType_HTML	HTML stream.
MFMediaType_Binary	Binary stream.
MFMediaType_FileTransfer	A stream that contains data files.

 

子类型

 

Creating Subtype GUIDs from FOURCCs and D3DFORMAT Values

These GUIDs have the form XXXXXXXX-0000-0010-8000-00AA00389B71, where XXXXXXXX is the 4-byte FOURCC code or D3DFORMAT value. 根据Fourcc来生成GUID！

 

If a video format has an associated FOURCC or D3DFORMAT value, you can create the corresponding subtype GUID as follows: Start with the constant MFVideoFormat_Base and replace the first DWORD of the GUID with the video FOURCC or the D3DFORMAT value. You can use the DEFINE_MEDIATYPE_GUID Macro for this purpose.

void DEFINE_MEDIATYPE_GUID(

      name,

      format

);

举例：

#include 

// Declares a GUID named MFVideoFormat_ABCD_Format.

DEFINE_MEDIATYPE_GUID( MFVideoFormat_ABCD_Format, FCC('ABCD') );

 

Note ：Directshow也可以用这种方式生成GUID，但是不压缩的RGB格式除外。但是Media Foundation中的不压缩RGB格式可以用这种方式生成。

 

 

Audio Subtype

GUID

The following audio subtype GUIDs are defined. To specify the subtype, set the MF_MT_SUBTYPE attribute on the media type.

GUID	Description
MFAudioFormat_Dolby_AC3_SPDIF	Dolby AC-3 audio over Sony/Philips Digital Interface (S/PDIF).
MFAudioFormat_DRM	Uncompressed but encrypted audio data used with secure audio path.
MFAudioFormat_DTS	Digital Theater Systems (DTS) audio.
MFAudioFormat_Float	Uncompressed IEEE floating-point audio.
MFAudioFormat_MP3	MPEG Audio Layer-3 (MP3).
MFAudioFormat_MPEG	MPEG-1 audio payload.
MFAudioFormat_MSP1	Windows Media Audio 9 Voice codec.
MFAudioFormat_PCM	Uncompressed PCM audio.
MFAudioFormat_WMASPDIF	Windows Media Audio 9 Professional codec over S/PDIF.
MFAudioFormat_WMAudio_Lossless	Windows Media Audio 9 Lossless codec or Windows Media Audio 9.1 codec.
MFAudioFormat_WMAudioV8	Windows Media Audio 8 codec, Windows Media Audio 9 codec, or Windows Media Audio 9.1 codec.
MFAudioFormat_WMAudioV9	Windows Media Audio 9 Professional codec or Windows Media Audio 9.1 Professional codec.

创建音频的subtype，要用MFAudioFormat_Base开头，再加上fourcc。这是规范写法。

 

创建不压缩的音频Media Type

下面这些属性是必须设置的：

Attribute	Description
MF_MT_MAJOR_TYPE	Major type. Set to MFMediaType_Audio.
MF_MT_SUBTYPE	Subtype. See Audio Subtype GUIDs.
MF_MT_AUDIO_NUM_CHANNELS	Number of audio channels
MF_MT_AUDIO_SAMPLES_PER_SECOND	Number of audio samples per second
MF_MT_AUDIO_BLOCK_ALIGNMENT	Block alignment 音频中最小的处理单位。 例如PCM，该值应为：声道数*每个sample的字节数
MF_MT_AUDIO_AVG_BYTES_PER_SECOND	Average number of bytes per second 码率
MF_MT_AUDIO_BITS_PER_SAMPLE	Number of bits per audio sample 采样位数
MF_MT_ALL_SAMPLES_INDEPENDENT	Specifies whether each audio sample is independent. Set to TRUE for MFAudioFormat_PCM and MFAudioFormat_Float formats. 设置每个音频sample是否是时间相关。

 

 

 

 

Video Subtype

GUID

创建音频的subtype，要用MFVideoFormat_Base开头，再加上fourcc。这是规范写法。

不压缩的RGB格式

GUID	Description
MFVideoFormat_ARGB32	RGB, 32 bits per pixel (bpp) with alpha channel.
MFVideoFormat_RGB24	RGB, 24 bpp.
MFVideoFormat_RGB32	RGB, 32 bpp.
MFVideoFormat_RGB555	RGB 555, 16 bpp. (Same memory layout as D3DFMT_X1R5G5B5.)
MFVideoFormat_RGB565	RGB 565, 16 bpp. (Same memory layout as D3DFMT_R5G6B5.)

Note  这些子类型和以前的不同，比如和Directshow中的子类型

YUV Formats: 8-Bit and Palettized

GUID	Format	Sampling	Packed or planar	Bits per channel
MFVideoFormat_AI44	AI44	4:4:4	Packed	Palettized
MFVideoFormat_AYUV	AYUV	4:4:4	Packed	8
MFVideoFormat_NV11	NV11	4:1:1	Planar	8
MFVideoFormat_NV12	NV12	4:2:0	Planar	8
MFVideoFormat_UYVY	UYVY	4:2:2	Packed	8
MFVideoFormat_YUY2	YUY2	4:2:2	Packed	8
MFVideoFormat_YV12	YV12	4:2:0	Planar	8

Most of these formats are described in detail in the following MSDN article: Video Rendering with 8-Bit YUV Formats. Two others are described here:

·         AI44 is a palettized YUV format with 8 bits per sample. Each sample contains an index in the 4 most significant bits (MSBs) and an alpha value in the 4 least significant bits (LSBs). The index refers to an array of YUV palette entries, which must be defined in the media type for the format.

·         NV11 is a 4:1:1 planar format with 12 bits per pixel. The Y samples appear first in memory. The Y plane is followed by an array of packed U (Cb) and V (Cr) samples. When the combined U-V array is addressed as an array of little-endian WORD values, the U samples are contained in the LSBs of each WORD, and the V samples are contained in the MSBs. (This memory layout is similar to NV12 although the chroma sampling is different.)

 

YUV Formats: 10-Bit and 16-Bit

GUID	Format	Sampling	Packed or planar	Bits per channel
MFVideoFormat_IYUV	IYUV	4:2:0	Planar	16
MFVideoFormat_P010	P010	4:2:0	Planar	10
MFVideoFormat_P016	P016	4:2:0	Planar	16
MFVideoFormat_P210	P210	4:2:2	Planar	10
MFVideoFormat_P216	P216	4:2:2	Planar	16
MFVideoFormat_v210	v210	4:2:2	Packed	10
MFVideoFormat_v410	v40	4:4:4	Packed	10
MFVideoFormat_Y210	Y210	4:2:2	Packed	10
MFVideoFormat_Y216	Y216	4:2:2	Packed	16
MFVideoFormat_Y410	Y40	4:4:4	Packed	10
MFVideoFormat_Y416	Y416	4:4:4	Packed	16

For more information about these formats, see 10-bit and 16-bit YUV Video Formats.

 

压缩视频类型

GUID	Description
MFVideoFormat_DV25	DVCPRO 25 (525-60 or 625-50).
MFVideoFormat_DV50	DVCPRO 50 (525-60 or 625-50).
MFVideoFormat_DVH1	DVCPRO 100 (1080/60i, 1080/50i, or 720/60P).
MFVideoFormat_DVSD	SDL-DVCR (525-60 or 625-50).
MFVideoFormat_DVSL	SD-DVCR (525-60 or 625-50).
MFVideoFormat_MP43	Microsoft MPEG 4 codec version 3. This codec is no longer supported.
MFVideoFormat_MP4S	ISO MPEG 4 codec version 1.
MFVideoFormat_MPEG2	MPEG-2 video. (Equivalent to MEDIASUBTYPE_MPEG2_VIDEO in DirectShow.)
MFVideoFormat_MPG1	MPEG-1 video.
MFVideoFormat_MSS1	Windows Media Screen codec version 1.
MFVideoFormat_MSS2	Windows Media Video 9 Screen codec.
MFVideoFormat_WMV1	Windows Media Video codec version 7.
MFVideoFormat_WMV2	Windows Media Video 8 codec.
MFVideoFormat_WMV3	Windows Media Video 9 codec.

 

创建不压缩的视频Media Type

 

YUV介绍

 

 

 

 

 

 

 

如何使用Media Foundation自带的例子

常用到的宏定义

请注意每个的声明

#define SAFE_RELEASE(x) { if (x != NULL) { x->Release(); x = NULL; } }

#define SAFE_DELETE(x) { if (x != NULL) { delete x; x = NULL; } }

#define SAFE_ARRAY_DELETE(x) { if (x != NULL) { delete [] x; x = NULL; } }

#define CHECK_HR(hr) { if (FAILED(hr)) { goto done; } }

 

宏使用举例

HRESULT Example()

{

    // Declare variables.

    HRESULT hr = S_OK;

    IUnknown *pUnk = NULL; // Initialize pointers to NULL.

    // Do work.

    CHECK_HR(hr = CreateAnObject(&pUnk));

    CHECK_HR(hr = UseTheObject(pUnk));

done:

// Control always jumps to this point on failure.

    // Clean up by releasing resources.

    SAFE_RELEASE(pUnk);

    return hr;

}

 

 

 

 

 

 

 

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作者：王琦    [email protected]

 

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