This class embodies the implementation of a specific codec instance used to transfer data via the logical channels opened and managed by the H323 control channel.
![]() | Open ( H323Connection & connection ) Open the codec. |
![]() | Close () Close the codec |
![]() | Read ( BYTE * buffer, unsigned & length, RTP_DataFrame & rtpFrame ) Encode the data from the appropriate device. |
![]() | Write ( const BYTE * buffer, unsigned length, const RTP_DataFrame & frame, unsigned & written ) Decode the data and output it to appropriate device. |
![]() | GetFrameRate () const Get the frame rate in RTP timestamp units |
![]() | OnFlowControl ( long bitRateRestriction ) Limit bit flow for the logical channel. |
![]() | OnMiscellaneousCommand ( const H245_MiscellaneousCommand_type & type ) Process a miscellaneous command on the logical channel. |
![]() | OnMiscellaneousIndication ( const H245_MiscellaneousIndication_type & type ) Process a miscellaneous indication on the logical channel. |
![]() | AttachChannel ( PChannel * channel, BOOL autoDelete = TRUE ) Attach the raw data channel for use by codec. |
![]() | CloseRawDataChannel () Close the raw data channel, described in H323Codec::AttachChannel |
![]() | deleteChannel connection to the hardware for reading/writing data. |
This class embodies the implementation of a specific codec instance used to transfer data via the logical channels opened and managed by the H323 control channel.An application may create a descendent off this class and override functions as required for descibing a codec.
A descendent class may be created by the application and it may cast the connection parameter to the application defined descendent of H323Connection to obtain information needed to open the codec.
The default behaviour does nothing.
The length parameter is filled with the actual length of the encoded
data, often this will be the same as OpalMediaFormat::GetFrameSize(). This function is called every GetFrameRate() timestamp units, so MUST
take less than (or equal to) that amount of time to complete. It
should always return the amount of data that corresponds to the
GetFrameRate() timestamp units as well. A returned length of zero indicates that time has passed but there is
no data encoded. This is typically used for silence detection in an
audio codec.
It is expected this function anunciates the data. That is, for example
with audio data, the sound is output on a speaker. This function is called every GetFrameRate() timestamp units, so MUST
take less than that amount of time to complete!
The channel connects the codec (audio or video) with hardware to read/write data.
Thus, the video codec provides a pointer to the data, which the renderer/grabber
then accesses to display/grab the image from/to.
virtual void Close()
virtual BOOL Read( BYTE * buffer, unsigned & length, RTP_DataFrame & rtpFrame )
length - Actual length of encoded data buffer
rtpFrame - RTP data framevirtual BOOL Write( const BYTE * buffer, unsigned length, const RTP_DataFrame & frame, unsigned & written )
length - Length of encoded data buffer
frame - Entire RTP frame
written - Number of bytes used from data buffervirtual unsigned GetFrameRate() const
virtual void OnFlowControl( long bitRateRestriction )
virtual void OnMiscellaneousCommand( const H245_MiscellaneousCommand_type & type )
virtual void OnMiscellaneousIndication( const H245_MiscellaneousIndication_type & type )
virtual BOOL AttachChannel( PChannel * channel, BOOL autoDelete = TRUE )
autoDelete - Channel is to be automatically deletedvirtual BOOL CloseRawDataChannel()
BOOL deleteChannel
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