RE: [midishare-devel] Soft-synth on Mac OS X

[Michael S. <ms...@ve...>]

Edwin,

Is it possible to send CoreMidi events with a future timestamp? If so,
you could do simple scheduling that way. It's been a long time since I
breifly looked at CoreMIDI, so I could easily be wrong.

Cheers,
Michael Stauffer
mi...@ci...
www.circular-logic.com

>-----Original Message-----
>From: mid...@li...
>[mailto:mid...@li...]On Behalf Of Edwin
>Vane
>Sent: Monday, June 27, 2005 9:01 AM
>To: MidiShare Devel
>Subject: Re: [midishare-devel] Soft-synth on Mac OS X
>
>
>On Mon, Jun 27, 2005 at 09:48:16AM +0200, St?phane Letz wrote:
>>
>> >I was hoping somebody close to midishare internals could quickly
>> >answer
>> >this question for me instead of me searching through the
>code. What is
>> >used as the software synth in Mac OS X in MidiShare? Is it the
>> >QuickTime
>> >synth or CoreMidi?
>>
>> The MidiShare driver msQTDriver still uses the QTMA
>architecture, but
>> we did not see hight latencies as you seems to have.
>> How do you measure this 100ms latency value?
>
>Through some simple user trials. I had a small animation of a bouncing
>ball and used QTMA to play some percussive sound at the exact
>millesecond the ball hit the plane (using the SMPTE midi time codes). I
>made a series of trials with the 'music' track offset from the video
>from about 300ms too early through 300ms too late. I just asked if the
>percussive sounds came before or after the ball bounce. Some statistics
>centered the latency around 100ms.
>
>Unless I was doing something wrong (although I did try very hard to make
>it work), the latency is pretty obvious when you play a quicktime movie
>that has a QTMA soundtrack alongside a video track.
>
>> >Via my experiments with QTMA in QuickTime (before I
>> >discovered QTMA was deprecatd), I discovered that QTMA in
>QuickTime is
>> >quite laggy (about 100ms in experiments). I ended up writing a new
>> >media
>> >handler that uses CoreMidi instead. However, when trying to play
>> >QuickTime movies with my new handler, playback can sound ever so
>> >slightly 'uneven' since movie players usually tell media players to
>> >play
>> >every 20 ms or so.
>>
>> Do you mean you're playing a MIDIFile with your new handler?
>
>Sort of. I came up with a new format for internal storage. QuickTime
>plays midi files by first converting them into QTMA info which is stored
>in tracks. My version of 'QTMA' is much more like midi (and pretty
>simple) since all I care about is passing events eventually to CoreMidi
>to play. So in theory, it's possible for my media handler to play
>standard midi files, I would just need to write a converter (like an
>Import Component).
>
>My problem is that my media handler is pretty simple and just plays all
>events that have occurred since the last time events were played up
>until the current point in time. Since the polling interval from your
>typical movie player is about 20ms, sometimes you get some detectable
>unevenness in the music (seeing as though our aural acuity is only a
>couple of milliseconds and I'm dealing with repetitive music).
>I was hoping for a simple solution to do basic
>scheduling to eliminate the unevenness.
>
>Edwin V
>
>
>
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