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Technote 1045

MAY 1996

This Note is aimed at all developers whose projects include QuickTime Conferencing.

Note:

The sections in this Technote refer to topics supported by different versions of QuickTime Conferencing. The title to each section includes the version of QTC in which that topic is first supported.

• Getting Stream Controller Errors When a Snapshot Fails,QTC 1.0.2
  
• Error Codes for MTFlowControlInit, QTC 1.0.2
  
• Conferencing MTRecorderChangedStreams & mtRenegotiatedErr, QTC 1.0.2
  
• QuickTime Conferencing Gestalt Selector Code, QTC 1.0.3
  
• PowerTalk Browser Notes
  
• Speaker Designation "Off While Recording" mislabeled
  
• MTTransportDisconnect does not return mtIncompatibleStateErr
  
• Interrupt-Time Processing with QTC Network Calls
  
• QTC SNMP MTallowedBandwidth MIB variable
  
• No QTC CFM-68K Support Yet
  
• Source Stream Director Restrictions
  
• Summary
  

Snapshot Failed Errors

Beginning with QuickTime 1.0.2, a stream controller uses the Component Manager function SetComponentInstanceError to convey the error in the case of a failed snapshot. If an application gets a NULL parameter for the mtControllerActionSnapshot or mtControllerActionSnapshotData action codes, it can then call the Component Manager function GetComponentInstanceError to find out the specific error number.

Further Reference

• Inside Macintosh: QuickTime Conferencing, Stream Control Components, Chapter 4
• Inside Macintosh: More Macintosh Toolbox, Component Manager, Chapter 6

New Error Codes for MTFlowControlInit

invalidComponentID
memFullErr

Further Reference

• Inside Macintosh: QuickTime Conferencing, Flow Control Components Chapter, 7-12

MTRecorderChangedStreams & mtRenegotiatedErr

Instead, the source and sink stream directors call the recorder's callback recording procedure routine, passing it a chunk with an the error field set to mtRenegotiatedErr. This indicates to the recorder that the stream formats and stream ID's have changed and that it needs to make the appropriate calls to the stream director to update the recording.

Developers of stream directors will need to call the recording procedure with a chunk which has the error field set to mtRenegotiatedErr whenever streams change when it is recording.

Developers of recorder components will need to look for the mtRenegotiatedErr value in the chunk error field of the media chunk and react appropriately to the new stream formats and ID's.

The error code mtRenegotiatedErr can be found in the QTC 1.0.2 interface files and is defined as follows:

mtRenegotiatedErr	-7886

Further Reference

• Inside Macintosh: QuickTime Conferencing, Recorder Components, Chapter 8, Stream Director Components, Chapter 5

New Gestalt Selector Code

#define gestaltQuickTimeConferencingInfo 'qtci'

The new Gestalt selector will return a pointer to the following structure:

struct QTCGestaltInfo {
	long QTCversion; /* standard binary version - i.e. 0x01044007 
						means "1.0.4a7" */
	char QTCversionString[20]; /* this is a pascal string, followed 
									by a zero char */
};

Warning:

Do not modify or dispose of the pointer to this structure - treat it as read-only information.

The reason for this is that version 1.0.2 of Apple Media Conference (also, therefore, Connectix VideoPhone) expects the same QTC version number as returned by the existing gestaltQuickTimeConferencing ('mtlk') Gestalt selector, and all the currently shipped 1.0.2 applications would have failed to run if the old selector was changed from its 0x01028000 value -- newer versions of QTC extensions essentially must lie about their version number to keep AMC 1.0.2 happy. Yes, that's also why Apple Media Conference 1.0.2 still says the QTC version is 1.0.2, even when a newer version of QTC is actually installed.

If the Gestalt selector points at a zero version number and empty string, it means that some QTC-related extension has already loaded, but QTC itself is not installed or has not yet loaded.

Note:

The QTCversionString is a Pascal string. Since there's a zero character after it, however, you can add one byte to the address and use it as a C string.

Further Reference

• Inside Macintosh: QuickTime Conferencing
• Inside Macintosh: Operating System Utilities, Gestalt Manager, Chapter 1

Also, when the PowerTalk browser is being used with the MTBrowserBrowse function, two additional errors not documented in the Browser chapter (chapter 3) of Inside Macintosh:QuickTime Conferencing may be returned:

invalidComponentID
memFullErr

Speaker Designation "Off While Recording" mislabeled

Since there exists a recording function within the Apple Media Conference application that is separate and distinct from the conference or broadcast functions, many users assume that the Off While Recording designation will turn the speakers off only when they elect to make a recording. In fact, it shuts off the speaker when a connection is made.

MTTransportDisconnect does not return mtIncompatibleStateErr

The MTTransportDisconnect function can legally be called at any time to clear the state.

Interrupt-Time Processing with QTC Network Calls

MTNetworkExtractName
MTNetworkOptions
MTNetworkSetNotifyProc
MTNetworkSetReceiveMediaProc

MTNetworkSend
MTNetworkReceive
MTNetworkSendMedia

No QTC CFM-68K Support Yet

Source Stream Director Restrictions

MTDirectorSetMatrix
MTDirectorSetRect
MTDirectorSetClip

Additionally, with QTC 1.0.2 (and above) it is possible to create a window that contains a sink view and its associated controller at some fixed offset (x,y) within the window. This is not currently possible for a given source view and its associated controller. A source controller may reside at some offset within a window but the corresponding source view must be placed at offset (0,0) in the same window. This behavior may be corrected in future versions of QTC.

Summary

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