[wdmaudiodev] Re: AVS and Midi
- From: "David Miller (MULTIMEDIA)" <davmil@xxxxxxxxxxxxx>
- To: <wdmaudiodev@xxxxxxxxxxxxx>
- Date: Thu, 2 Oct 2003 10:11:01 -0700
Hi Guenter,
Yes it is true that the standard MIDI Port code in Portcls.sys will
expand running status before returning it in KSMUSICFORMAT chunks.
As for the timestamp issue, it does appear that as far as capture is
concerned only the TimeDeltaMs is filled in by the MIDI Port code. The
render code does appear to be using both the presentation time and the
TimeDeltaMs for its timestamp. I don't think I fully understand your
question, though - what exactly are you trying to accomplish?
::Dave Miller
-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Guenter
Hildebrandt
Sent: Thursday, October 02, 2003 7:58 AM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] AVS and Midi
Hi,
I'm developing a AVStreaming driver linked with ks.sys under Windows XP.
The driver has a Filter with a Midi source pin. I get the data from the
hardware as a byte stream without limits. I indicate the midi data using
the data structure KSMUSICFORMAT as a header for each buffer. It seems
that Windows requires a complete Midi message in each buffer. So I have
implemented a Midi parser which knows the size of each Midi sample and
assembles the midi messages. Midi allows a special mode called "running
mode", where the device sends a command e.g. 0x90 (note on) and data for
several notes with out repeating the command. Now my question: Is it
correct that the parser translate the following message
0x90 0x34 0x45 0x35 0x45 0x36 0x45
into
Buffer 1: 0x90 0x34 0x45 (note on, note 0x34, after touch 0x45) Buffer
2: 0x90 0x35 0x45 Buffer 3: 0x90 0x36 0x45 The driver changes the data
stream in this case.
If the parser works like this:
Buffer 1: 0x90 0x34 0x45 (note on, note 0x34, after touch 0x45) Buffer
2: 0x35 0x45 Buffer 3: 0x36 0x45 programs like CuBase does not get the
notes 0x35 and 0x36.
A second problem is the time stamping of Midi data. The DDK says: put a
presentation time stamp in the KSSTREAM_HEADER and in the
KSMUSICFORMAT.TimeDeltaMs the relative presentation time. This does not
work with Cubase. All notes are put to time 0. During experiments I have
found the following solution:
- no presentation time in KSSTREAM_HEADER
- the complete timing in KSMUSICFORMAT.TimeDeltaMs, the time stamp is
derived from the system time.
- the zero point is set on the call SetDeviceState: KSSTATE_RUN
With this method I can loop a midi stream through my hardware. The first
time I do so with Cubase I get a time delay of -30ms. The recording data
are 30 ms before the playing data. The second and all further runs I get
a delay of 8 ms which may the delay in the hardware. This implementation
is very different to the documentation.
Can somebody give me a hint or comment to this.
Thanks
Guenter
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