Interfaces Reference

This section defines the interfaces needed to add audio and video codec formats for use with NetMeeting.

Create_Instance
IInstallAudioCodecs
IInstallVideoCodecs

Create Instance

Use the standard COM CreateInstance API to instantiate a CInstallCodecs object with the CreateInstallCodecs interface. For more information on Create Instance, see Inside OLE, Second Edition.

CreateInstallCodecs

HRESULT CreateInstallCodecs(
    LPUNKNOWN punkOuter,
    REFIID riid,
    LPVOID * ppv);

Creates an instance of the CInstallCodecs object, and returns the requested interface. This function should only be called indirectly through CoCreateInstance.

Returns one of the following values:

S_OK	Success.
E_INVALIDARG	Invalid argument.
E_OUTOFMEMORY	Not enough memory to create the object.
CLASS_E_NOAGGREGATION	Aggregation is not supported for this object.
IC_E_CAPS_INSTANTIATION_FAILURE	Could not instantiate a capability object.
IC_E_CAPS_INITIALIZATION_FAILURE	Could not initialize a capability object.

punkOuter: Pointer to an indicator that reveals whether or not the object is part of an aggregate.
riid: Reference to the identifier of the interface.
ppv: Indirect pointer to the requested interface.

CreateInstallCodecs should not be called directly. Clients of installable codecs should use the COM CoCreateInstance function to instantiate the object, expecting the same return values.

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This interface provides methods for adding audio codec formats for use with NetMeeting, as well as removing these formats, enumerating them, and changing their use order.

AddACMFormat
EnumFormats
FreeBuffer
RemoveACMFormat
ReorderFormats

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IInstallAudioCodecs::AddACMFormat

HRESULT AddACMFormat(
    LPWAVEFORMATEX lpwfx,
    PAUDCAP_INFO pAudCapInfo);

Adds an ACM encoding format for use with NetMeeting.

Returns one of the following values:

S_OK	Success.
E_INVALIDARG	Invalid argument.
IC_E_NO_SUCH_FORMAT	The specified WAVEFORMATEX structure was not found with ACM. The format must be installed with ACM before it can be added for use with NetMeeting.
IC_E_INTERNAL_ERROR	The network audio/video controller reported a system error.

lpwfx: Address of the WAVEFORMATEX structure of the format to add.
pAudCapInfo: Additional format information that is not in the WAVEFORMATEX structure.

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IInstallAudioCodecs::EnumFormats

HRESULT EnumFormats(
    PAUDCAP_INFO_LIST * ppAudCapInfoList);

Enumerates the audio codec formats known to NetMeeting.

Returns one of the following values:

S_OK	Success.
E_INVALIDARG	Invalid argument.
E_OUTOFMEMORY	Not enough memory for allocating the enumeration buffer.
IC_E_NO_FORMATS	No formats were available to enumerate.
IC_E_INTERNAL_ERROR	The network audio/video controller reported a system error.

ppAudCapInfoList: Address of a pointer to an AUDCAP_INFO_LIST structure that lists the enumerated formats.

The caller is expected to free the returned list by calling IInstallAudioCodecs::FreeBuffer on the same interface.

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IInstallAudioCodecs::FreeBuffer

HRESULT FreeBuffer(
    LPVOID lpBuffer);

Frees a buffer that was returned by the IInstallAudioCodecs interface.

Returns S_OK if the function was successful.

lpBuffer: Address of the buffer to free. This buffer must have been allocated by one of the IInstallAudioCodecs methods.

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IInstallAudioCodecs::RemoveACMFormat

HRESULT RemoveACMFormat(
    LPWAVEFORMATEX lpwfx);

Removes an ACM format from the list of formats used by NetMeeting.

Returns one of the following values:

S_OK Success.
E_INVALIDARG Invalid argument.
IC_E_NO_SUCH_FORMAT The specified format was not found.
IC_E_INTERNAL_ERROR The network audio/video controller reported a system error.

lpwfx: Address of the WAVEFORMATEX structure for the format to remove.

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IInstallAudioCodecs::ReorderFormats

HRESULT ReorderFormats(
    PAUDCAP_INFO_LIST pAudCapInfoList);

Reorders the audio formats for use with NetMeeting.

Returns one of the following values:

S_OK Success.
E_INVALIDARG Invalid argument.
C_E_INTERNAL_ERROR The network audio/video controller reported a system error.

pAudCapInfoList: Address of the AUDCAP_INFO_LIST structure containing a pointer to the list of formats to reorder and the number of formats in the list.

Since this method can only reorder formats that are known to NetMeeting, it is recommended that the caller first call IInstallAudioCodecs::EnumFormats to get all formats known to NetMeeting, assign new sort indexes (wSortIndex), and then call IInstallAudioCodecs::ReorderFormats with the modified list.

Arranging the formats in a specific order by using IInstallAudioCodecs::ReorderFormats does not guarantee that the top-ranked formats will be used before lower-ranked formats are used. For example, if the sending system is not capable of encoding a top-ranked format, this format will not be used. The same will happen if the receiving system cannot decode this format.

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IInstallVideoCodecs

This interface provides methods for adding video codec formats for use with NetMeeting, as well as removing these formats, enumerating them, and changing their use order.

AddVCMFormat
EnumFormats
FreeBuffer
RemoveVCMFormat
ReorderFormats

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IInstallVideoCodecs::AddVCMFormat

HRESULT AddVCMFormat(
    PVIDCAP_INFO pVidCapInfo);

Adds a video encoding format for use with NetMeeting.

Returns one of the following values:

S_OK	Success.
E_INVALIDARG	Invalid argument.
IC_E_NO_SUCH_FORMAT	The specified format was not found. The format must be installed with Video For Windows before it can be added for use with NetMeeting.
IC_E_INTERNAL_ERROR	The network audio/video controller reported a system error.

pVidCapInfo: Pointer to the address of the structure.

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IInstallVideoCodecs::EnumFormats

HRESULT EnumFormats(
    PVIDCAP_INFO_LIST * ppVidCapInfoList);

Enumerates the video codec formats known to NetMeeting.

Returns one of the following values:

S_OK	Success.
E_INVALIDARG	Invalid argument.
E_OUTOFMEMORY	Not enough memory for allocating the enumeration buffer.
IC_E_NO_FORMATS	No formats were available to enumerate.
IC_E_INTERNAL_ERROR	The network audio/video controller reported a system error.

ppVidCapInfoList: Address of a pointer to a VIDCAP_INFO_LIST structure that lists the enumerated formats.

The caller is expected to free the returned list by calling IInstallVideoCodecs::FreeBuffer on the same interface.

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IInstallVideoCodecs::FreeBuffer

HRESULT FreeBuffer(
    LPVOID lpBuffer);

Frees a buffer that was returned by the IInstallVideoCodecs interface.

Returns S_OK if the function was successful.

lpBuffer: Address of the buffer to free. This buffer must have been allocated by one of the IInstallVideoCodecs methods

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IInstallVideoCodecs::RemoveVCMFormat

HRESULT RemoveVCMFormat(
    PVIDCAP_INFO pVidCapInfo);

Removes a video format from the list of formats used by NetMeeting.

Returns one of the following values:

S_OK Success.
E_INVALIDARG Invalid argument.
IC_E_NO_SUCH_FORMAT The specified format was not found.
IC_E_INTERNAL_ERROR The network audio/video controller reported a system error.

pVidCapInfo: Address of the VIDCAP_INFO structure describing the format to remove.

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IInstallVideoCodecs::ReorderFormats

HRESULT ReorderFormats(
    PVIDCAP_INFO_LIST pVidCapInfoList);

Reorders the video formats for use with NetMeeting.

Returns one of the following values:

S_OK Success.
E_INVALIDARG Invalid argument.
IC_E_INTERNAL_ERROR The network audio/video controller reported a system error.

pVidCapInfoList: Address of the VIDCAP_INFO_LIST structure containing a pointer to the list of formats to reorder and the number of formats in the list.

Since this method can only reorder formats that are known to NetMeeting, it is recommended that the caller first call IInstallVideoCodecs::EnumFormats to get all formats known to NetMeeting, assign new sort indexes (wSortIndex), and then call IInstallVideoCodecs::ReorderFormats with the modified list.

Arranging the formats in a specific order by using IInstallVideoCodecs::ReorderFormats does not guarantee that the top-ranked formats will be used before lower-ranked formats are used. For example, if the sending system is not capable of encoding a top-ranked format, this format will not be used. The same will happen if the receiving system cannot decode this format.

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