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Events

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Alexander Bashlykov
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Events help you to monitor what happens with objects that you operate. There are 2 types of events: 

  • OnFrame (OnFrameSafe) - raises on each processed frame. Available only in MPlatform SDK. With MFormats SDK you control each frame separately so there is no need in such events.
  • OnEvent (OnEventSafe) - raises when each significant event happens with an object.

Difference between -Safe events and usual events

The difference between OnEventSafe and OnFrameSafe events is noticeable only with .Net-based languages, e.g. C# and VB.Net. The -Safe events were implemented to avoid objects handles leakage specific to the way .Net technology works with COM objects. 

For Delphi and C++ you should use OnEvent and OnFrame events through IMCallback interfaces. See the article about memory release issues for additional information.

How to implement events for different languages?

C#

//Form_Load method
//initialize events
m_objPlaylist.OnEventSafe += new MPLATFORMLib.IMEventsEvent_OnEventSafeEventHandler(m_objPlaylist_OnEvent);
m_objPlaylist.OnFrameSafe += new MPLATFORMLib.IMEventsFrame_OnFrameSafeEventHandler(m_objPlaylist_OnFrame);


void m_objPlaylist_OnEvent(string bsChannelID, string bsEventName, string bsEventParam, object pEventObject)
        {
            if (bsEventName == "EOF")
            {
                int nIndex, nNextIndex;
                double dblFileTime, dblListTime;
                m_objPlaylist.PlaylistPosGet(out nIndex, out nNextIndex, out dblFileTime, out dblListTime);
            }
        }

C++

static HRESULT OnEvent(LONGLONG lCallbackCookie, BSTR bsChannelID, BSTR bsEventName, BSTR bsEventParam, IUnknown* pEventObject);
static HRESULT OnFrame(LONGLONG llCallbackUserData, BSTR bsChannelID, IUnknown* pMFrame);

Note that for C++ onFrame event you should set "object::on_frame.sync" property to "true"

HRESULT CLiveSourceSampleDlg::OnEvent(LONGLONG lCallbackCookie, BSTR bsChannelID, BSTR bsEventName, BSTR bsEventParam, IUnknown* pEventObject)
 return S_OK;
};
HRESULT CLiveSourceSampleDlg::OnFrame(LONGLONG llCallbackUserData, BSTR bsChannelID, IUnknown* pMFrame)
{
 return S_OK;
};
For LiveSource sample:
 LONGLONG cookie = 0;
 LONGLONG onEvt = (LONGLONG)&(CLiveSourceSampleDlg::OnEvent);
 LONGLONG onFrm = (LONGLONG)&(CLiveSourceSampleDlg::OnFrame);
 m_objLive->ObjectCallbackSetFunc(onEvt, onFrm, (LONG_PTR)cookie);

Delphi

// 1. Create a custom class TEvents
TEvents = class (TInterfacedObject, IMCallback)
    function OnEvent(lCallbackCookie: LONG_PTR; const bsChannelID: WideString;
                     const bsEventName: WideString; const bsEventParam: WideString;
                     const pEventObject: IUnknown): HResult; stdcall;
    function OnFrame(lCallbackCookie: LONG_PTR; const bsChannelID: WideString;
                     const pMFrame: IUnknown): HResult; stdcall;
  end;
// 2. On Form Load procedure create a TEvents class object
m_objEvents := TEvents.Create();
// 3. Start to listen this events with ObjectCallbackSet method
m_pObject.ObjectCallbackSet(m_objEvents, cookie);
// 4. Create these functions
function TEvents.OnEvent(lCallbackCookie: LONG_PTR; const bsChannelID: WideString;
                     const bsEventName: WideString; const bsEventParam: WideString;
                     const pEventObject: IUnknown): HResult; stdcall;
var
nRows, nIndex, nNextIndex : integer;
dblFileTime, dblListTime : Double;
begin
   if (bsEventName = 'EOF') then begin
      nRows := Form2.dataGridViewFiles.RowCount;
      Form2.m_objPlaylist.PlaylistPosGet(nIndex, nNextIndex, dblFileTime, dblListTime);
     if (nRows > 2) and (nIndex <= nRows - 2) then
        Form2.dataGridViewFiles.Row := nIndex + 1;
   end;
end;
function TEvents.OnFrame(lCallbackCookie: LONG_PTR; const bsChannelID: WideString;
                     const pMFrame: IUnknown): HResult; stdcall;
begin
end;

Please also note that for HTML plugin in Delphi you should use the IMFObject to set callback both in the MPlatform and MFormats.

m_objOverlayHTML := CreateComObject(CLASS_MFOverlayHTML) as IMFBrowser;
(m_objOverlayHTML as IMFObject).MFCallbackSet(m_objEvents, cookie);

Windows Service events

delegate void CallbackDelegateEvent(long llCallbackUserData, Int32 bsChannelID, Int32 bsEventName, Int32 bsEventParam, Int32 pEventObject);
delegate void CallbackDelegateFrame(long llCallbackUserData, Int32 bsChannelID, Int32 pFrame);
// --------------------------------------- OnEvent ----------------------------------------------------------- //
GCHandle gchCallbackDelegateOnEvent;
void OnEvent_as_Callback()
{
    eventLog1.WriteEntry("OnEvent_as_Callback starting...");
    CallbackDelegateEvent callbackDelegate = TheCallbackEvent;
    IntPtr callbackDelegatePointer = Marshal.GetFunctionPointerForDelegate(callbackDelegate);
   
    GC.Collect();
    gchCallbackDelegateOnEvent = GCHandle.Alloc(callbackDelegate); // !!!!
    m_objFile.ObjectCallbackSetFunc(callbackDelegatePointer.ToInt64(), 0, 0);
    GC.Collect();
    eventLog1.WriteEntry("OnEvent_as_Callback done.");
}
public void TheCallbackEvent(long llCallbackUserData, int bsChannelID, int bsEventName, int bsEventParam, int pEventObject)
{
    // Convert this pointer
    object pThis = ((GCHandle)new IntPtr(llCallbackUserData)).Target;
    // Convert string
    string strChannel = Marshal.PtrToStringBSTR(new IntPtr(bsChannelID));
    // Convert string
    string strEventName = Marshal.PtrToStringBSTR(new IntPtr(bsEventName));
    // Convert string
    string strEventParam = Marshal.PtrToStringBSTR(new IntPtr(bsEventParam));
   
    eventLog1.WriteEntry("OnEvent!!! " + llCallbackUserData + " " + strChannel + " " + strEventName + " " + strEventParam);
}

// --------------------------------------- OnFrame ----------------------------------------------------------- //
GCHandle gchCallbackDelegateOnFrame;
void OnFrame_as_Callback()
{
    eventLog1.WriteEntry("OnFrame_as_Callback starting...");
    CallbackDelegateFrame callbackDelegateFrame = TheCallbackFrame;
    IntPtr callbackDelegatePtr = Marshal.GetFunctionPointerForDelegate(callbackDelegateFrame);
    IntPtr callbackThisPtr = (IntPtr)GCHandle.Alloc(this);
    GC.Collect();
    gchCallbackDelegateOnFrame = GCHandle.Alloc(callbackDelegateFrame);
    m_objFile.ObjectCallbackSetFunc(0, callbackDelegatePtr.ToInt64(), callbackThisPtr.ToInt64());
    GC.Collect();
    eventLog1.WriteEntry("OnFrame_as_Callback done.");
}
public void TheCallbackFrame(long llCallbackUserData, Int32 bsChannelID, Int32 pFrame32)
{
    // Convert this pointer
    object pThis = ((GCHandle)new IntPtr(llCallbackUserData)).Target;
   
    // Convert string
    string strChannel = Marshal.PtrToStringBSTR(new IntPtr(bsChannelID));
    // Convert pFrame
    IMFFrame pMFrame = (IMFFrame)Marshal.GetObjectForIUnknown(new IntPtr(pFrame32));
   
    // Check frame
    M_TIME mTime;
    pMFrame.MFTimeGet( out mTime );
    eventLog1.WriteEntry("OnFrame!!! " + pThis + " " + strChannel + " " + mTime.tcFrame.nExtraCounter);
}

Available events for objects

MFile

The bsChannelID shows a path to the currently initialized file.

  • "start" - raises the moment playback is started.
    bsEventParam:
        "" - simple start of playback.
        "loop" - restart of the file if it is in a "loop" state.
  • "pause" - raises the time you set the object in pause state by the FilePlayPause method.
    bsEventParam is a duration of the pause.
  • "EOF" - raises when the file reaches its end.
    bsEventParam:
        "stop" - the file stops at the end.
        "loop" - the file is in "loop" state.
  • "stop" - raises the time you set the object in stop state by the FilePlayStop method.
    bsEventParam is a duration of the stop.
  • "connect" - raises at the moment a network stream is connected or disconnected.
    bsEventParam:
        "false" - the stream is disconnected.
        "true" - the stream is re-connected.
  • "watch-dog" - raises the moment a watch-dog triggers some event.
    bsEventParam:
        "object-locked"
        "error-access"
        "file-freeze"
        "file-failed"
        "update"
        "update-failed"
  • "SCTE35" - raises the moment an SCTE-35 trigger is received. As bsEventParam it uses a parsed SCTE-35 message string.
  • "connect" - raises when the stream connected/diconnected.
    bsEventParam:
        "true" - stream connected to the object.
        "false" - stream disconnected.

MLive & MFLive

  • "no_signal" - raises when a source signal is lost ("No Video Signal" message appears).
    Possible bsEventParam values: true (the signal is lost) and false (the signal is restored).
  • "format_changed" - raises the moment a source video format is changed. bsEventParam shows the name of a new video format.
  • "SCTE35" - raises the moment an SCTE-35 trigger is received. As bsEventParam it uses a parsed SCTE-35 message string.
  • "SCTE104" - raises the moment an SCTE-104 trigger is received. As bsEventParam it uses a parsed SCTE-104 message string.

MPlaylist

  • "switch" - raises the moment playlist switches from one item to another.
    bsEventParam:
        "from" - indicates a previous item (a path to a file or an object name) as the bsChannels parameter.
        "to" - indicates the item (a path to a file or an object name) as the bsChannels parameter.
  • "playlist-command" - raises the moment an MPlaylist executes a command. Indicates a command as the bsChannels parameter.
  • "playlist_add" - raises the moment you add a new item with the PlaylistAdd method. Shows a name of the MPlaylist object as the bsChannels parameter.
    bsEventParam is a target index of a new item.
  • "playlist_remove" - raises the moment you remove an item with the PlaylistRemove or the PlaylistRemoveByIndex methods. Shows a name of the MPlaylist object as the bsChannels parameter.
    bsEventParam is a target index of a removed item.
  • "EOL" - raises the moment the playlist is over. Shows a name of the MPlaylist object as the bsChannels parameter.
  • "pause" - raises the time you set the object in pause state by the FilePlayPause method.
    bsEventParam is a duration of the pause.
  • "start" - raises the moment the object is started with the ObjectStart method.
  • "stop" - raises the time you set the object in stop state by the FilePlayStop method.
    bsEventParam is:
        a duration of the stop
        "stop-done" - raises when stop time is over and playback is resumed.
        "error-OutOfMemory" - raises when the playlist is stopped because of an OutOfMemory exception.
  • "EOF" - raises the moment an item is over.
  • "break-command" - raises the moment a break command is executed.
    bsEventParam is:
        a position of a break
        "error-execute" - indicates that command can't be executed.
  • "break-start" - raises the moment a break is started.
    bsEventParam is:
        a position of a break
        "error-start" - indicates that a break can't be started.
  • "break-done" - raises the moment a break is over.
  • "SCTE35" - raises the moment an SCTE-35 trigger is received. As bsEventParam it uses a parsed SCTE-35 message string.
  • "connect" - raises when the stream connected/diconnected.
    bsEventParam:
        "true" - stream connected to the object.
        "false" - stream disconnected.

MWriter 

bsChannelID is the name of an object.

  • "file-close" - raises the moment when the encoded file is available for usage by the system. Available for both MWriter and MFWriter object.
    bsEventParam is a path to the encoded file. 
  • "error-abort" - raises on any error during recorder. Available for MFWriter only.
    bsEventParam can be "disk-full" (raises when the target disk is full) or an error code.
  • "switch" - raises the moment you switch from one destination to another.
    bsEventParam is a path to the encoded file.
  • "start" - raises the moment the encoding is started.
    bsEventParam is a path to the encoded file.
  • "stop" - raises the moment you stop the encoding.
    bsEventParam is a path to the encoded file.
  • "file-close-info" - raises the moment when the encoded file is available for usage by the system.
    bsEventParam is information about a file.
  • "disk-full" - raises when the target disk is full.
  • "end-of-media" - raises when the end of a source is reached.
  • "max-switch" - raises when the maximal amount of switches is reached.

MFWriter

  • "file-close" - raises the moment when the encoded file is available for usage by the system. Available for both MWriter and MFWriter object.
    bsEventParam is a path to the encoded file. 
  • "error-abort" - raises on any error during recorder. Available for MFWriter only.
    bsEventParam can be "disk-full" (raises when the target disk is full) or an error code.

bsChannelID is the name of an object.

MMixer

  • "scene_active_set" - raises the moment you set an active scene.
    bsEventParam indicates whether the active scene is set ("true", "false").
  • "pause" - raises the time you set the object in pause state by the FilePlayPause method.
    bsEventParam is:
        duration of the pause.
        "pause-done" - indicates that the pause is over
        "pause-start" - indicates that the pause is started
  • "start" - raises the moment you start the object with the ObjectStart method.
  • "stop" - raises the moment you set the object in stop state by the FilePlayStop method.
    bsEventParam is a duration of the stop.
  • "source_disconnected" - raises when a stream is disconnected.
  • "source_connected" - raises when a stream is connected back.
  • "disconnect" - raises when you remove a stream with the StreamsRemove method.
  • "connect" - raises when you add a stream with the StreamsAdd method.

MPreview

  • "wpf_nextframe" - raises on each received frame in wpf_preview=true mode. See the article about WPF Preview for more details.
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