How many midi events per second can a midibox handle?

[gm02froe]

Hi

The problem I am confronted with is probably a unique one in this forum: I am using the midibox for my px1m0d project (http://www.maybites.ch/tikiwiki/tiki-index.php?page=px1m0d, it has been introduced last fall), and I want to play movies on the display (8x8 = 64 pixels or rather 12v lamps).

now beside the fact that it is a unique widescreen experience, I have the limitation that controlling px1m0d via max/msp it can only play about 10frames (or 640 midi events) without starting to lag behind.

the effect is thus, that while max/msp keeps producing the midievents, it looks as if the events are stored until they can be passed on. there is obviously a bottleneck, I I wonder where it might be.

a -  the midi - protocol can handle only so much events (1600(8x8x25) events per second is certainly beyond every virtuos musicians abilities)

b - the midibox is too slow (I know its very fast, but fast enough?)

c - the problem is max/msp or my computer, in this case I would be rather happy...

or maybe d?

cheers

martin

[stryd_one]

Hi MayBites :)

I have to ask lots of questions so I can get a better idea of the situation before I can help. Can you tell me:

So what framerate are you running at? Have you tried slowing to something very slow like 1 frame per 2 seconds? Does that work? Hae you Captured the output from MAX to a MIDI file? How many bytes are you sending? Are they evenly spaced or do they slow down in the file too? Are there any bytes being sent which are unnecessary or unwanted? Have you tried sending this MIDI file out to the px1m0d from a midi file player of some sort (Cut max out of the loop)? Do I ask too many questions?  :)

[TK.]

Hi Martin,

from the MIOS application side this shouldn't be a big problem, because the transmission of a single MIDI event takes 960 uS, and the app. will propably process this within 50 or 100 uS. Even if your host program gets use of the "running status" feature (in this case only two bytes need to be sent for a 3byte MIDI event), it should be ok.

I think that not MIDI itself is the problem, but the protocol you are using.

You could control the lamps with a significantly higher framerate by using SysEx streams. Instead of sending one 3-byte event for each CV out, you could send 2 + 64 bytes instead (F0 <64 bytes> F7)

The resulting frame rate would be 1 / (320 uS * 66) = 47 frames per second

With the C application I sent you this can be realized without much effort, I guess that I also gave you this hint some time ago

Best Regards, Thorsten.

[stryd_one]

See this is why we all worship TK, he obviously know the answers to some of my questions before you even answered  ;D

TK, the Omnipotent One! hehehe

[gm02froe]

Hi all

thanks both of you for your quick reply! even though nothing is clear, it sounds marvelous.

TK: The project was put on hold for the last 5 months, and I didnt want to fiddle around with the midibox-application during troubleshooting, at least not until now, because I need the "running status" feature. I will get back to you as soon as I have results.

stryd_one: I hope u dont mind me skiping your questions, because it looks as if TK's lead makes perfect sense, though I hope now that the C-compile tutorial for beginners will do the trick! and that its possible to send sysex messages with max.

cheers

martin

[stryd_one]

stryd_one: I hope u dont mind me skiping your questions, because it looks as if TK's lead makes perfect sense, though I hope now that the C-compile tutorial for beginners will do the trick! and that its possible to send sysex messages with max.

It's all good mate :) I wouldn't have bothered answering all those questions, obviously TK has some inside knowledge on this subject.

MAX/MSP can definitely send sysex :)