Midi In

[Joerg Koehler]

Hello,

In one of my projects I need to retrieve the Midi input for regular Midi messages such as “Note on” (up to 3 bytes) and
also system exclusive messages (more than 3 bytes).
I am using the example code below to do so.

I have 2 Midi interfaces available, Emagic’s Unitor 8 and M-Audio Firewire Audiophile.

The code works very well with Unitor 8. No problems at all.
Only if I use the M-Audio interface, I got crashes as soon as I feed long system exclusive messages (267 bytes) and short regular messages
into the input simultaneously.

It would be very nice if somebody could check the code to point me to the culprit.

Thank you very much in advance!

Joerg

<script type="text/javascript">
<!--
#COMPILE EXE
#DIM ALL

%USEMACROS = 1
#INCLUDE "Win32API.inc"


'==============================================================================
FUNCTION WINMAIN (BYVAL hInstance     AS DWORD, _
                  BYVAL hPrevInstance AS DWORD, _
                  BYVAL lpCmdLine     AS ASCIIZ PTR, _
                  BYVAL iCmdShow      AS LONG) AS LONG
'------------------------------------------------------------------------------
    ' Program entry point
    '--------------------------------------------------------------------------

    LOCAL Msg       AS tagMsg
    LOCAL wce       AS WndClassEx
    LOCAL szAppName AS ASCIIZ * 80
    LOCAL hWnd      AS DWORD

    ' Setup and register a window class for the main window
    ' CODEPTR is used to pass the address of the function that will
    ' receive all messages sent to any window created with this class
    szAppName         = "Midi In Test"
    wce.cbSize        = SIZEOF(wce)
    wce.STYLE         = %CS_HREDRAW OR %CS_VREDRAW
    wce.lpfnWndProc   = CODEPTR(WndProc)
    wce.cbClsExtra    = 0
    wce.cbWndExtra    = 0
    wce.hInstance     = hInstance
    wce.hIcon         = %NULL
    wce.hCursor       = LoadCursor(%NULL, BYVAL %IDC_ARROW)
    wce.hbrBackground = %COLOR_BTNFACE + 1
    wce.lpszMenuName  = %NULL
    wce.lpszClassName = VARPTR(szAppName)
    wce.hIconSm       = LoadIcon(hInstance, BYVAL %IDI_APPLICATION)

    RegisterClassEx wce

    ' Create a window using the registered class
    hWnd = CreateWindow(szAppName, _               ' window class name
                        "Midi In Test", _          ' window caption
                        %WS_OVERLAPPEDWINDOW, _    ' window style
                        %CW_USEDEFAULT, _          ' initial x position
                        %CW_USEDEFAULT, _          ' initial y position
                        400, _                     ' initial x size
                        200, _                     ' initial y size
                        %NULL, _                   ' parent window handle
                        %NULL, _                   ' window menu handle
                        hInstance, _               ' program instance handle
                        BYVAL %NULL)               ' creation parameters

    IF hWnd = 0 THEN  ' exit on failure
        MSGBOX "Unable to create window"
        EXIT FUNCTION
    END IF

    ' Display the window on the screen
    ShowWindow hWnd, iCmdShow
    UpdateWindow hWnd

    ' Main message loop:
    ' Messages sent to HELLOWIN while it has the focus are received by
    ' GetMessage().  This loop translates each message and dispatches it
    ' to the appropriate handler.  When PostQuitMessage() is called, the
    ' loop terminates which ends the application.
    DO WHILE GetMessage(Msg, %NULL, 0, 0)
        TranslateMessage Msg
        DispatchMessage Msg
    LOOP

    FUNCTION = msg.wParam

END FUNCTION

'==============================================================================
FUNCTION WndProc (BYVAL hWnd AS DWORD, BYVAL wMsg AS DWORD, _
                  BYVAL wParam AS DWORD, BYVAL lParam AS LONG) EXPORT AS LONG
'------------------------------------------------------------------------------
    ' WndProc is the message handler for all windows creating using the HelloWin
    ' class name.  A single WndProc procedure can handle multiple windows by
    ' testing the hWnd variable passed to it.
    '--------------------------------------------------------------------------

    LOCAL  midiErr        AS LONG
    LOCAL  ptMidiInHdr1   AS MIDIHDR PTR
    LOCAL  ptMidiInHdr2   AS MIDIHDR PTR
    LOCAL  ptMidiInHdrRet AS MIDIHDR PTR
    LOCAL  hdrDummy       AS MIDIHDR
    LOCAL  lMidiIn        AS LONG
    STATIC hWndIn         AS DWORD
    STATIC hWndOut        AS DWORD
    LOCAL  lBuffSize      AS LONG
    LOCAL  sStatus        AS STRING * 2
    LOCAL  sNote          AS STRING * 2
    LOCAL  sVelo          AS STRING * 2
    STATIC lBuffRet       AS LONG
    STATIC lInreset       AS LONG
    LOCAL  lcount         AS LONG

    ' The SELECT CASE is used to catch only those messages which the message
    ' handler needs to process.  All other messages are passed through the
    ' tests to the default handler.
    SELECT CASE wMsg

    CASE %WM_CREATE

        lMidiIn   = 8
        lBuffSize = 384

        midiErr = midiInOpen(hWndIn, BYVAL lMidiIn, BYVAL hWnd, 0, %CALLBACK_WINDOW OR %MIDI_IO_STATUS)

        'no input available
        IF ISTRUE midiErr OR ISFALSE hWndIn THEN

           lBuffRet = 3

           SetWindowText hWnd, "No valid input available!"

           EXIT FUNCTION

        END IF

        ptMidiInHdr1 = HeapAlloc(GetProcessHeap(), %HEAP_ZERO_MEMORY, LEN(hdrDummy))
        ptMidiInHdr2 = HeapAlloc(GetProcessHeap(), %HEAP_ZERO_MEMORY, LEN(hdrDummy))

        'prepare Midi header1
        @ptMidiInHdr1.lpdata          = HeapAlloc(GetProcessHeap(), %HEAP_ZERO_MEMORY, lBuffSize)
        @ptMidiInHdr1.dwbufferlength  = lBuffSize
        @ptMidiInHdr1.dwbytesrecorded = 0
        @ptMidiInHdr1.dwUser          = 1 'indicates buffer number
        @ptMidiInHdr1.dwFlags         = 0

        'prepare Midi header2
        @ptMidiInHdr2.lpdata          = HeapAlloc(GetProcessHeap(), %HEAP_ZERO_MEMORY, lBuffSize)
        @ptMidiInHdr2.dwbufferlength  = lBuffSize
        @ptMidiInHdr2.dwbytesrecorded = 0
        @ptMidiInHdr2.dwUser          = 2 'indicates buffer number
        @ptMidiInHdr2.dwFlags         = 0

        midiErr  = midiInPrepareHeader(BYVAL hWndIn,  BYREF @ptMidiInHdr1, LEN(hdrDummy))
        midiErr  = midiInPrepareHeader(BYVAL hWndIn,  BYREF @ptMidiInHdr2, LEN(hdrDummy))

        midiErr  = midiInAddBuffer(BYVAL hWndIn, BYREF @ptMidiInHdr1, LEN(hdrDummy))
        midiErr  = midiInAddBuffer(BYVAL hWndIn, BYREF @ptMidiInHdr2, LEN(hdrDummy))

        midiErr  = midiInStart(BYVAL hWndIn)

    CASE %MM_MIM_DATA

        sStatus = MID$(HEX$(lParam, 6), 5, 2)
        sNote   = MID$(HEX$(lParam, 6), 3, 2)
        sVelo   = MID$(HEX$(lParam, 6), 1, 2)

        'display regular midi events
        SetWindowText hWnd, sStatus & "," & sNote & "," & sVelo

        EXIT FUNCTION

    CASE %MM_MIM_LONGERROR

         ptMidiInHdrRet = lParam

         midiErr = midiInAddBuffer(BYVAL hWndIn, BYREF @ptMidiInHdrRet, BYVAL LEN(hdrDummy))

    CASE %MM_MIM_LONGDATA

        ptMidiInHdrRet = lParam

        IF ISFALSE(lInReset) THEN

           'display SysEx midi events
           SetWindowText hWnd, CHR$(@ptMidiInHdrRet.lpdata)

           midiErr = midiInAddBuffer(BYVAL hWndIn, BYREF @ptMidiInHdrRet, BYVAL LEN(hdrDummy))

        ELSE


           lBuffRet = lBuffRet + @ptMidiInHdrRet.dwUser

           midiErr  = midiInUnprepareHeader(BYVAL hWndIn,  BYREF @ptMidiInHdrRet, LEN(hdrDummy))

           midiErr  = HeapFree(GetProcessHeap(), %HEAP_NO_SERIALIZE, @ptMidiInHdrRet.lpdata)
           midiErr  = HeapFree(GetProcessHeap(), %HEAP_NO_SERIALIZE, ptMidiInHdrRet)

        END IF

       EXIT FUNCTION

    CASE %WM_CLOSE

        lInReset = %TRUE

        midiErr = midiInReset(BYVAL hWndIn)

        WHILE lBuffRet <> 3
           DIALOG DOEVENTS 1 TO lCount
        WEND

        midiErr = midiInClose(BYVAL hWndIn)

    CASE %WM_DESTROY
        PostQuitMessage 0
        EXIT FUNCTION

    END SELECT

    ' Any message which is not handled in the above SELECT CASE reaches this
    ' point and is processed by the Windows default message handler.
    FUNCTION = DefWindowProc(hWnd, wMsg, wParam, lParam)

END FUNCTION
//-->
</script>

[Michael Mattias]

I don't know if this is your problem but...

WHILE lBuffRet <> 3
           DIALOG DOEVENTS 1 TO lCount
WEND

Don't use "DDT" syntax when using SDK-style coding; and I would avoid embedding message loops in the window procedure, since you already have a message loop.

Also, while I know nothing specfic about these 'midi' functions...

   midiErr = midiInAddBuffer
   ...
  midiErr  = midiInUnprepareHeader 
 ...

You are not checking for the success or failure of these functions; e.g. according to the doc for the "unprepareheader" function...

Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error values include the following.

Value Description
MIDIERR_STILLPLAYING The buffer pointed to by lpMidiInHdr is still in the queue.
MMSYSERR_INVALPARAM The specified pointer or structure is invalid.
MMSYSERR_INVALHANDLE

For sure I'd be checking those returns and if not the "NOERROR" value I'd be doing "something."

MCM

[Joerg Koehler]

Message loop

Thank you Michael for your suggestions.

About the DoEvents stuff...

The question for me is how to wait within WM_CLOSE for the
return of the pending buffers? If I send midiInReset, then the driver
marks all pending buffers as done and sends the pointer to it
back to the callback by using %MM_MIM_LONGDATA. This could take time
and is async. Since I don't want to close the midi devices by hand before
closing the app, i have to do that in WM_CLOSE.
I suspect, WaitForSingleObject would block the whole thread and
the message loop would never react to %MM_MIM_LONGDATA, wouldn't it?

About checking midiInUnprepareHeader...
The code above is only a sample code. The real code does of course check
for success or failure. But it is to big to post in here. I could reduce
the important things to make it simpler to describe.

Joerg

[Michael Mattias]

>The code above is only a sample code. The real code...

Golly, I love this job....

[Joerg Koehler]

Why should I post hundreds of lines of code if this example code has exactly
the same problem??? It crashes in the same way!!!

[Michael Mattias]

First of all, it's because I would not have bothered to look up those "midi" calls and what they returned had I seen that you were, in fact, doing this 'Programming 101' thing, that's why posting 'sample' code which is not the same as the 'code of interest' is such a crummy thing to do.

But on to your problem..

If the idea is you have a user interface, and want to make sure that you close down stuff, and closing down requires you receive and process notifcation messages...

I would probably run the whole "midi" interface to call back to an invisible, separate window, a window which runs in its own thread of execution.

But you might be able to get away with 'what you have' by....

1. When you get WM_CLOSE, disable the main window so no user input can get in
2. Eat the WM_CLOSE; do not allow the default processing (which is DestroyWindow)
3. Post a private message to the window which means "effect shutdown" and exit the window procedure.
4. Process the shutdown message. If you need to set up a PeekMessage() loop to do so, you can do that.
5. When shutdown processing is complete, post yourself a "shutdown complete" message
6. When processing the "shutdown complete" message, just call DestroyWindow yourself.

But I prefer my initial idea... run all the midi* stuff in a separate window which executes in the context of another thread of execution. That will have the "fringe benefit" of keeping the midi* code physically separate from the "hundreds of [other] lines of code" and a lot easier to debug and maintain.

MCM

[Joerg Koehler]

Okay, but also if the midi stuff runs in a different thread, what he now does,
still have to wait for the execution of this thread. Can I do this within the WM_CLOSE by using WaitforSingleObject?

[Michael Mattias]

>Can I do this within the WM_CLOSE by using WaitforSingleObject

No. WFSO suspends calling thread until the wait condition is satisfied. Wel, I suppose you could do this if you run all the midi stuff in another thread, but now your user interface won't update in response to moving and you'll get those blank rectangles on the screen.

Basically I am saying you are to use WM_CLOSE ONLY to initiate your 'shutdown' sequence, and NOT allow WM_CLOSE to destroy the window.

But since you say you are now using the multi-thread approach....

You can wait for your shutdown function to end back in WinMain... and there you could use WFSO, waiting on the thread handle.

eg

FUCNTION WinMain...

  CreateWindow  (User interface)
  ShowWindow

  THREAD CREATE (midi window create and message loop) ... to hThreadMidi

  ' message loop to process user interface window
  WHILE GETMESSAGE (...

  WEND
 ' ------------------------------------------------------------
'  Program gets here after UI window posts quit message. 
' ------------------------------------------------------------

  ' Wait for shutdown function to end before ending program
   WFSO   hthreadMidi, timeout
   THREAD CLOSE hThreadMidi TO retvar 
END FUNCTION  ' winmain

MCM

[Joerg Koehler]

Okay, I have to run a shutdown sequence while the main windows is still existing because
the threads I am waiting for to determine are dealing with quasi global variables which are stored in a structure and
the pointer to this structure is stored in the extra bytes of the main window. This global structure would not exist anymore
if I wait for the threads after the main window is destroyed. So now the threads are sending application defined messages to the
disabled Main window when they have finished and this works great and reliable.

Thank you for your suggestions,

Regards,
Joerg