Error 15 MIDI Input Buffer Overflow

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I’m done developing my MT project, at least, all features work.  I still have a problem which I’ve mentioned before. I thought I would leave it for last since it has been so hard to pin down.  It makes my project unusable for performance, which is pretty devastating to me since I’ve spent quite a few years getting it to this point.

I’m wondering if there is any way for me to “trap” the offending inputs as they are received and execute code in MT.  The log window (if it is turned on) shows the message that it’s truncated, so I can’t tell from that, what has happened.  Maybe some software is available to help with that?

In any case, I would be glad to send you my code so that you could look it over.  There are more than 400 presets and over 60,000 lines of code and comments when exported as text, but I’ve disabled all presets that aren’t involved in the problem, leaving less than 20 presets in order to make inspecting the code easier.

I can describe the problem generally this way:
It’s intermittent, in the sense that I can do the same things successfully with my controllers many times over, but then out of the blue, I get the error. 15 message  The offending controller then neither sends or receives any MIDI to/from MT, but turning it off and then on restores the connection (with the MT message “MIDI Buffer OK”.

Until I do this, I’m not even able to exit MT completely.  If I exit, and try to launch MT again, I get messages telling me that the ports for my controllers are already being used.  I notice then that though MT doesn’t appear in the Apps section of Task Manager, it does appear in the Background processes section and I can’t end the task.  I have to restart my computer.
I can usually force the error by grabbing 8 or 9 faders on my AKAI APC Mini and scrubbing them back and forth as rapidly as I can.  Sometimes the error appears fairly quickly – after maybe 2 or 3 repetitions, but sometimes I can keep scrubbing for 10, 15 or more repetitions before I get the error.  This is especially true if I’ve deactivated some of my presets.
I’ve tried to isolate the problem by disabling presets that I suspect could be causing the problem, but even with only quite essential presets still active, I’m still having the error.

I think the problem may be that for most of the inputs that are receiving faders, any one message is being received by many presets and many translators within them.  That is because fader movement controls several aspects of my program.

At any rate, I’m stumped and frustrated that I can’t really use my program to play for people.  any help would be much appreciated.

Thanks,

Gabriel

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Posted by (Forum: 51, Answers: 211)
April 24, 2018 11:35 am
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Hi Gabriel,

 

From what you said, I assume you have pinned this down to the APC mini.  Is this the device you need to power cycle to correct the problem?  If for some reason, you are not seeing it in the log file, and you have a Windows machine (which I’m sure you do).  Maybe you can try and capture the point of error in MIDI OX?

I’m happy to take a quick look at the project file if you either post it here or email it to me. I have an APC MINI so maybe I can duplicate the error.  I suspect you have a lot of MIDI traffic with such a complex file so may not be able to duplicate your situation however without artificially generating some more MIDI traffic. So a sense of what MIDI traffic is occurring when you are having the problem would be helpful. Is there also any or much MIDIBuddy traffic when this occurs?

Regards,

Steve

 

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Posted by (Forum: 50, Answers: 5077)
April 24, 2018 3:26 pm
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Hi Steve,

Yes, the APC Mini’s cause the error, but I think any controller with several faders or  pots mapped to my project would cause the error as well.  And, yes, there’s a lot of traffic, but you’ll be able to see it for yourself since you have an APC Mini.  Only one is necessary 🙁

I’ll send you a copy of my program which has all but a few presets disabled.  This serves to highlight the offending sections of the code. I’ll also send a copy of the Live set which is similarly simplified to make it easier to analyse.

When I last posted about this problem, Florian had mentioned the possibility of increasing the size of the input buffer.  I believe I wouldn’t have a problem with increased response time given the way I trigger samples, so I guess that might be a final option to consider if there’s not actually a fixable bug in my code.

Thanks,

Gabriel

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Posted by (Forum: 51, Answers: 211)
April 25, 2018 12:22 am

OK, Gabriel. I will watch for your email.

Steve

( at April 25, 2018 12:32 am)
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Hi Steve,

Here are the simplified files for Live and MT Pro.  I’ve deleted all MT Pro code that doesn’t pertain to the problem I’m having- so now you only need to regard a handful of Presets instead of 400.

In Live, I’ve also deleted all but 3 tracks and 8 scenes, all returns, and all effects so that you can load the file.

I’ll check to see if I send Fader info to APC’s anywhere. I think I only send back LED on/off messages, but sometimes there are a lot of them.  For two reasons….

1)  I sometimes need to turn on only one of the 8 LEDs for the round buttons.  Only one should be lit at a time to tell me which row has an active clip.  I don’t keep track of which LED is on, so I turn them all off and then turn on the one I want lit.  Of course I could have used the LEDs under the rectangular buttons to tell me which clip is playing, but I use them to tell me if I’m using Reverb or Delay or Low End Boost or EQ in that track, or one of several other effects.
2)  I think I may be sending the same message repeatedly in response to the fader movement.  Now, I can’t remember if I limit that.  I used to do it with a timer that suppressed sending of the messages – limiting them to once in 500ms, I think.  Then I tried another method, but ultimately, I’m not sure if I do that anymore.
Looks like the Live file is still to big to attach.  I’ll send it to you directly.
Thanks,
Gabriel

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Posted by (Forum: 51, Answers: 211)
April 25, 2018 8:32 pm
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OK, I was able to do some testing. Here is what I did.

  1. Moved the faders of APC MINI really fast like you said and yes it hung after a few moments.
  2. Used Bome SendSX to send button data really fast to APC MINI. No problem at full speed with over 64K of data.
  3. Did the same above with SendSX execept used fader data instead of button data. No problem
  4. Opened MIDI OX.  Set up loopback from APC MINI to APC MINI with monitoring on. Moved faders fast for about 30 seconds.  It hung. Was not able to close MIDI OX (just like MT Pro) until after unplugging and re-plugging in the APC MINI.

So my deduction is that there is a problem in the APC MINI or Windows 10 driver when quickly both sending and receiving same fader data over a period of time over a period of time.  It appears to crash the APC40 and hang the Windows driver. Of course when you unplug the device, the Windows driver deletes it which clears the problem and you can close the application. Then you plug it back in and everything is back to normal.

My recommendation, ensure that fader data is never sent to the APC MINI.  I don’t think button data would be a problem but then again, I cannot push buttons on the APC MINI fast enough to determine if a similar problem would happen with buttons if I could.

I hope this helps!

 

Steve

 

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Posted by (Forum: 50, Answers: 5077)
April 25, 2018 10:45 pm

Thanks for this analysis. I think you’re telling me this:
You set up Midiox to receive data from the APC and then to send it back into the APC…. a loop.

And that it’s not that MT Pro is receiving data too fast from the faders, but, instead, that MT Pro is sending too much data for the APC to digest so quickly. Or maybe you’re saying that it takes both sending and receiving of that data to crash the APC.

I didn’t think I was ever sending raw fader messages back to the APC. Are you seeing CC messages going to the APC when running my project, or just Note On/Note Off messages intended to turn the LEDs on or off? If there are CC messages being sent to the APC, I wouldn’t have intended that and should be able to fix it.

If it’s note on/off messages, I should be able to limit the flow one way or another.
Thanks,
Gabriel

( at April 25, 2018 11:07 pm)

Hi fingerlight, chiming in… at first let me tell you how much I understand how annoying this must be for you. Steve’s isolated test might indeed indicate that the APC driver has a problem with too much data being sent to the APC when it is also receiving a lot. You could enable ONLY the MIDI IN and MIDI OUT checkboxes in the Log Window and see what’s being logged there (that way, the log shouldn’t get truncated so soon).
Are you using version 1.8.2 or 1.8.3 beta?

( at April 25, 2018 11:38 pm)

The reason I used MIDI OX is to try and determine if it a MT Pro problem or not. Duplicating the problem in MIDI OX sort of confirms the problem must lie somewhere else.

For the test with Ableton Live, the last logged data was note data, however maybe the issue is that when APC MINI is sending fader data fast while it is also receiving any data, it would hang. I can’t actually send anything but fader data that fast with the APC MINI. So maybe that is it. I don’t know if it is Windows driver problem or APC MINI problem or combination of both. You say it only hangs with the APC MINI so I have to lean in that direction.

( at April 25, 2018 11:49 pm)

Hi Steve,
The version of my project without MIDI data being sent to the APC Mini still has the problem. I will say that removing the preset which starts a timer whenever a volume fader is moved does seem to make it harder to produce the error, though I can still do it.
So, is it a bad idea to repeatedly start a 500 ms timer… 125 times in maybe 1/2 second?
And again, if I’m never sending data to the APC, , it seems that’s not the root cause anyway.
Thanks,
Gabriel

( at April 25, 2018 11:59 pm)

I’ll try to test using the Novation Zero SL to see if it has the same problem.
BTW, just letting you know that I sent a simplified MT Pro file to you just now. It might have gotten lost in the flurry of messages.

( at April 26, 2018 12:01 am)
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Steve,

I disabled all outputs to the APC.  Now I’m sending MIDI only to Live and to instance 2 of MT Pro (which isn’t running)  I’m still sending to instance 2 to see if that causes problems.

Here’s a potential problem.  In order to throttle sends to instance 2 (I only need to send one MIDI message to instance 2 for a fader movement) I use a timer that blocks transmission until the timer expires.  What I notice is that when I move a volume fader through its entire range, the timer gets started about 125 times.  Is that potentially gumming up the works?  I’ll eliminate it and also the sends to Instance 2 to see what happens, tho I think I’ve done that test once already.

Thanks,

Gabriel

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Posted by (Forum: 51, Answers: 211)
April 25, 2018 11:32 pm

I don’t think changing the timer will do anything. It is strange you are still having the problem. What is the last MIDI message the log shows when it fails and to what device was it sent?

( at April 26, 2018 2:15 am)
I just sent 19205 bytes of button data at full speed several times using Bome SendSX with no problem. Then I tried it while moving the faders at the same time and the port hung. I could not close SendSX until I unplugged and re-plugged in the APC MINI. I think I test it with a different controller and see if the other one has the same problem. I will test with APC40 MK2. That might narrow it down to the driver.
( at April 26, 2018 2:20 am)
The problem does not duplicate when sending massive button data to APC40 MK2 or my Worlde Easycontrol.9. Did you say you tried turning all output off going to the APC MINI to see if the problem still occurs?
( at April 26, 2018 2:23 am)

Yes… I did turn off all output going to the APC Mini. The latest “Simplified” bmtp file I sent disables all sends to the Mini. I still get the problem. You’ll find that file attached to my answer to Florian’s post. It’s called “Simplified Test for MIDI Input Buffer Overflow WITH NO midi to APC.bmtp”

I’m wondering what output you ever see going back to the APC. Do you see anything other than 90 xx yy (LED on/off)? So it seems that sending massive amounts of button data to the MINI hangs it if the faders are moving at the same time, but that this doesn’t hang the APC40.

I also did a test with another controller… the Novation Zero SL. My heart sank when I saw that I couldn’t make it hang. That’s good news as far as that controller goes, but not so good in terms of my setup which is largely built around the Mini’s They’re the only controllers with the particular configuration of buttons and faders I needed. So I have 8 of them at this point. I’m inextricably bound to using them.

Still another test I did was to simply to hang the Mini by moving its faders (a lot) while sending the output to Midiox (but not returning any MIDI to the Mini. It doesn’t hang, as you also pointed out with a similar test.)

Getting AKAI to do anything about the controllers is probably very unlikely. I tried to reach them about another issue with the Mini’s quite a while ago and could never get anything like real attention from them.

It seems strange, though that without any MIDI going to the MINI, it hangs under some conditions (lots of fader movement). I’m going to recheck this to see that there’s absolutely nothing going to the MINI with the latest “Simplified” bmtp.

If the problem really seems to be related to simultaneous input and output from the Mini, perhaps you’ll be willing to help me revamp my code so that simultaneous i/o is somehow prevented or at least throttled to the point that the error is eliminated… but let’s see what further testing comes up with.
Thanks,
Gabriel

( at April 26, 2018 2:50 am)

Tested with the following other controllers (while moving faders or knobs)
Novation Launchkey MINI – OK
Samson Conspiracy – Hang when moving faders but not when leaving static
Novation Launch Control – OK
Novation Launch Control XL – OK

That is all I have to test with that has faders or knobs.

Yes, I’m only sending notes

( at April 26, 2018 2:57 am)
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Hi Florian,
Thanks for your input, and for the commiseration.
I’m using 1.82
I believe that the problem is not generated by sending data to the APC. I simplified the code so that no MIDI is ever sent to the APC and still got the error message.

I thought I had posted a simplified version of my project, but now see that I sent the Live file instead, so I’ll send the simplified project file now. It has only the pertinent sections of code and no MIDI sent to the APC.
Also, I disabled the timer which throttles messages sent to a second instance of MT Pro. I think I just discarded the post which describes how I’m using the timer, so I’ll explain again.
First – I’m only running one instance of MT Pro right now, so that’s not a consideration. When I do use the second instance, I need to send information from instance 1 to instance 2 whenever a fader is moved, I just need to send it once, but the message would get sent many many times as the fader continues to move, so I instituted a timer that throttles the send until the timer expires. The problem is that the timer gets launched about 125 times as the fader moves through its entire range. Can launching a timer so often create a problem. The timer has a period of 500ms I think.

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Posted by (Forum: 51, Answers: 211)
April 25, 2018 11:53 pm

timers can be launched as often as you like, they’re designed to work that way.

( at April 26, 2018 9:58 pm)
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Hi Steve,

You’ve helped a lot by pinning down the cause of the error condition to the APC Mini driver (or perhaps the Windows driver).  I think you’re exactly right.

What has been confusing is that sometimes the first swipe of a fader or two can cause the error, but other times I can furiously “scrub” 8 faders for many repetitions before the error occurs.  I think I now understand the problem better.  I think it’s purely by chance that MT sends a MIDI message to the APC at the exact same moment as the APC is outputting a message to MT Pro.  When an APC volume fader is swept through its entire range:

  • The APC sends 128 MIDI CC values (0->127) for a full sweep of the fader.
  • MT responds, among other messages, with the following MIDI string every time it receives one of these values, so, for a full sweep it sends the string 128 times!!!:

90 52 00 90 53 00 90 54 00 90 55 00 90 56 00 90 57 00 90 58 00 90 59 00 90 ss 01

Where ss = a number between 52 and 59 (hex)

You might ask why I’m turning off all LEDs and then turning on just one of them.  It’s clumsy, but explaining why I do that would be a distraction here.   It has to do with the fact that I don’t have anymore global variables to store the LED states.  But I won’t discuss this for now.

There’s a pretty good chance that given this amount of traffic, eventually there will be the type of collision that freezes the APC driver, disabling any communication with MT.  I’m not sure just what nuances of movement cause the timing that produces a collision.  Maybe it’s just luck combined with some slight variations in the speed at which messages are flying back and forth….something like that.

Solution 1:   A solution might be to somehow block MT from sending MIDI to the APC while it’s receiving MIDI from the APC.  I think that would be tricky but may be possible.  Do you have an idea how this could be coded?

Solution 2:  Another solution might be to reserve one particular button for each track (I have 24 buttons per track that launch clips – I could spare one of them and still have 23).  Instead of launching a clip, it would instruct MT pro to send the stream described above (8 LEDs off and then one of them on) to the APC.  I’ve tried doing this with one track and it seems to prevent the error.  I’ll need to test more before I commit to changing my code for all tracks.  I think I could also figure out a way to reduce the MIDI stream sent to the APC by turning off only the LED that’s on before turning on the new one, but I need more globals to do that, and just don’t have them.

Can you think of another way to prevent simultaneous in/out MIDI to and from the APC?  Or some other unrelated solution?

In any case, I’m feeling much better now since it feels as if a solution might be at hand.

Thanks,

Gabriel

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Posted by (Forum: 51, Answers: 211)
April 26, 2018 10:13 am

Hi Gabriel,

Solution 1 is probably your best bet but you would need another global variable. You simply set the variable to 1 and put a rule in each translator bound for the APC MINI as follows:

if ga==1 the exit rules, skip outgoing action
When the APC MINI is ready for more rules you set the global variable (ga in this example) back to 0 and then
the translator will fire on the next input.

As far as global variables are concerned. How many states are you tracking with each button. Every global variable is a 32 bit signed integer so there may be a bit mapping technique you can use to take more advantage or the 32 to bits available for a single global variable. I can track 64 button on/off states with just 2 global variables, each button representing a single bit of the global variable. If you want to track 3-4 states it would take 2 bits. For 5-8 states (colors) it would take 3 bits. So with a single variable with 8 color states, you could track 10 buttons with a single variable. If interested, I can send you an example of how this is done,

The other way you could disable input without using a global variable is to put all APC MINI incoming messages under a separate preset, and the a translator to disable/enable that preset as needed. If you need to enable/disable multiple presets, you would need to use a single timer event that fire multiple translator, each disabling/enabling a different preset.

We may also need to look at the APC MINI manual. I know on the Novation products you can turn on/off LED’s with Sysex messages instead of note messages. If APC MINI supports this, maybe it would be more reliable, than sending multiple note messages. I’m not sure if APC MINI supports this however.

Steve

( at April 26, 2018 3:52 pm)

Hi Steve,
For solution 1, I can’t think of a way to tell when the APC would be ready to accept more MIDI messages. Are you thinking of using a timer (as shown below)? Else how would I know when it’s safe to send data to the APC?

(ga=0 when MT is launched)
In Translator 1) Start a timer in response to the a fader movement.
In Translator 2) If ga=0 Send an LED message back to APC, but block output if ga=1.
In Translator 2) Set ga=1 if ga=0 on entering translator.
When timer elapses reset the global (ga=0)

When the timer expires, reset the global to 0 – at which point, Translator 2 allows output.

I think the above would work, but I have a concern. As the fader moves through its entire range, it starts the timer for each increment of the fader… so 127 times. To be effective, the timer probably needs to have a period of at least 100ms. Wouldn’t that cause a major bottleneck?… 127 timers all running at the same time – or maybe many hundreds of timers when I move several faders at the same time. Or does the same timer merely get reset each time it is started if it’s already running?

As for using the bit mapping to represent more than one LED, I’ve looked into that, and, in fact I began to do that a while back, but it would have required a lot of re-writing, and I’m loathe to do it. Instead of doing it, I chose to use a 2nd instance of MT to take on some of the load, (and provide extra variables). Using the 2nd MT seems not to be a problem, since I encounter the problem eve when running only one instance.

Disabling and reenabling presets whose function is to send MIDI to the APC is an interesting twist on the previous strategy. I’ll see if I can test it successfully, but wouldn’t it pose the same problem as strategy 1? How would I know when it’s safe to receive MIDI again so I can start transmitting data to the APC?

As for Sysex, AKAI is notorious for not being helpful to people seeking more esoteric info, and there’s nothing in the tiny manual that defines sysex for the Mini.
Thanks,
Gabriel

( at April 26, 2018 9:18 pm)

Hi, your timer strategy looks good. You wouldn’t launch 127 timers, it would just be the same timer restarting.
I would set it up so that any MIDI output sets the variable to 1 and then launches the timer.. You could use
raw incoming message of pp qq rr and then not use them in the rules. That would cover any 3 byte incoming message from the APC MINI. I suspect a setting of 10msec would give it enough time to get ready for the next incoming message. Keep in mind you may lose the message coming from Ableton Live if it reacts quickly but if you are controlling the LED’s yourself, you should be able to manage the return traffic in MT Pro. If you need reliable messages back from Ableton Live while timer is in place, we would need some sort queuing system which of course would require more global variables. Of course Ableton would never send back fader data so maybe best to limit return input only when moving faders and not pushing buttons.

As far as preset enabling, disabling. You would still use a timer but the you would disable the preset in one translator and start a timer in the other using the same incoming MIDI trigger, When the timer completes, it would then re-enable the preset.

Too bad about AKAI not providing that type of input. Many manufactures seem to have hidden features that would be very valuable if they documented them. Yesterday I found out quite by accident how to turn on LED’s on my Samson Conspiracy controller. I found this when testing whether it would crash like the APC MINI.

Yes, bit mapping although effective can be a bear to set up and sometimes I even go back and try to figure out how I did things. Replacing single digit in a variable is easy if you are taking it from 0 to 1. It is a simple OR operation.
However to take it from 1 to 10 you have to XOR the initial variable, then AND the bit and then XOR the original value (if I remember), to get it back with the change. Also sometimes remember which bits are used for what can be challenging especially if you are dealing with multiple bits for an LED (IE 3 bits for RGB).

Take care.

Steve

( at April 26, 2018 9:42 pm)

Why don’t you throttle the data sent to the AKAI?
1) use a global variable (I know you’re short on them) to store the value of ss
2) instead of sending the long string, start timer “LED Update”, one-shot, delay 20ms
3) in Incoming Timer “LED Update” translator, send the long string with the global variable instead of ss

Like that, the LED update will only be sent 30ms after the fader stops moving. It’ll also update if the fader is moved so slowly that it fires less than 30ms in succession.

If you want the LED’s to continuously update even while you’re quickly moving faders, there’s a solution for that, too. But the above is more elegant.

( at April 26, 2018 10:01 pm)
Hi Florian. I didn’t suggest this due to his lack for global variables. Also Ableton may send either short or long MIDI messages in bursts so we never know what pattern to look for unless it is just a 3 byte message but if they send multiple 3 byte messages in bursts, you would need variables for them all if you have to queue them all. I suppose if I got really agressive, I could look at the Ableton Python script itself so I could either determine a pattern of what it will send or modify the script to something that is more predicable by MT Pro. I could probably even put in a delay for returning data to the controller every time Ableton got a MIDI message and queue up the messages there in the Python script. I’m not up to the challenge of this complexity, however at this time. Steve
( at April 26, 2018 10:18 pm)

Steve and Florian,
Thanks to both of you for all the attention you’re giving to this issue.

Live doesn’t play a role in the problem. The error occurs even when Live isn’t running. Beyond that, when I do have Live running, MT sits between Live and all my controllers, so any message from Live is analyzed by a translator in MT, and only messages I want to use make it past that translator. (The translator is called “Control Track Enable with Feedback from Ableton (to eliminate early audition of masked clips”, and is near the end of my project). I was able to decipher the messages Live was sending by using Midiox to monitor them.

The challenge I see is to determine when the APC Mini can accept MIDI without crashing (presumably when the APC faders are not moving). I think you are both suggesting similar strategies using a timer – either to block input from the APC or to block output to the APC once MT receives a fader movement. And since I now know that the timer would be restarted rather than to start a whole slew of timers, I feel comfortable taking this approach.
I do something similar in order to throttle MIDI sends to MT instance 2. I should have known the timer was being restarted because I can see that timer being sent out many many times, but only being acted upon once.

It doesn’t matter if the LED states are updated with significant delay. I use the LEDs only once in a while, when I want to see which clips are playing.

I believe I may have freed up a few globals in recent tinkering with the code, and if I still don’t have enough, I should be able to offload some more routines to MT instance 2, thereby freeing up enough globals.

I’ll leave this thread as not resolved so far and update as soon as I’ve proven that we have a solution.
I have a good feeling about this now.
Thanks,
Gabriel

( at April 26, 2018 11:29 pm)

Great, keep us posted. We are here to help if needed.

( at April 26, 2018 11:58 pm)
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Testing is going well so far.

I’ve limited the testing to two APC Mini’s.  In MT Pro, I’ve disabled any translators that output to LEDs in response to fader movement.  Live is also running.  Button presses do still output to LEDs.

Among other actions, a button press may send a MIDI string that turns off 8 LEDs and turns one of them back on…. so 9 commands sent as a single output from MT.  Something new I’ve learned is that I can do this while scrubbing several faders vigorously.

Because I can do that, I believe the APC only hangs when it receives MIDI while a fader is moving.  Sending and receiving at the same time seems to be ok as long as the sending is being done by pressing buttons.  I’ve “squashed down” on as many buttons simultaneously as I can and at the same time scrubbed as many faders as I can grab onto without causing a hang.

Before I did this experiment, I tried the strategy of using a timer to disable MIDI outputs to the APC if a fader was moving.  I think I wasn’t careful about making sure every potential output situation had been treated because I could still cause the hang, but I’m going about things much more methodically now.

My next step will be to enable – one at a time – MIDI outs to the APC’s but include the throttling we discussed.

I’ll let you know how things go.

Gabriel

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Posted by (Forum: 51, Answers: 211)
April 27, 2018 10:17 am

Hi, maybe we should also open up a ticket with Akai Pro about this problem? Since both of us can duplicate it, apparently it is not a problem to a specific controller but to all APC minis. Maybe they can come out with a firmware fix?

( at April 27, 2018 2:09 pm)

I called AKAI today, trying to get support for this issue, but it was like crashing into a brick wall. I was told that the Mini was developed to interface directly with Live, and that if there was 3rd party software in between the two, they wouldn’t consider any firmware changes. They also said that they didn’t have any information about sysex for the Mini.

This was their support line, not a direct connection with the developers of he Mini, but they told me there was no way to get in contact with those developers. I’ve had a similar interaction with them in the past about a different issue with the Mini.

Then I tried Ableton support, where, at least, I had a sympathetic ear. I asked if they might have sysex info for the Mini, since they were involved in its development. Sympathy notwithstanding, they were unable to give me that information. Not really sure if they didn’t have it or were under obligation not to divulge it. Of course, again, I was dealing with someone quite far from the engineers involved.

So, I’ll try, now, to re-instate LED feedback, a step at a time, to see if I can isolate the cause of the problem more specifically, and then build in some kind of throttling or a timing change, in order to allow me to control the LEDs without hanging the Mini.

Since it doesn’t matter if it takes a few seconds to get the visual feedback I need, it might work to delay the output to the Mini (though there’s always a chance that I’d resume moving a fader just at the time that I’m updating the LEDs).

Or maybe just sending the LED messages one LED at a time rather than all 9 in the output of one translator as a single string would do the trick. I’ll give it a try also.
Thanks for all your help.
Gabriel

( at April 27, 2018 9:10 pm)

I also opened a support ticket with Akaipro but used their support forum and pointed them to this post for details.

( at April 27, 2018 9:21 pm)

Thanks for doing that. It would be great if that approach bears fruit.

( at April 28, 2018 11:51 pm)
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Private answer

Hi Steve and Florian,

My second try at solving the Error 15 issue seems to be very promising.  It’s very much along the lines that both of you have been describing.

Originally, if I scrubbed a fader quickly, and update the LEDs as shown below the APC eventually freezes.

  • MT Pro Input from AKAI APC track volume fader:                     B1 pp qq
  • Response from MT Pro (output to Live track volume fader):    B1 pp qq
  •                                   and
  • Response from MT Pro (output to APC) for updating LEDs:
  • —  90 52 00 90 53 00 90 54 00 90 55 00 90 56 00 90 57 00 90 58 00 90 59 00 90 ss 01
  • —  Where ss is the LED I want to turn on.  All LEDs are turned off before turning ss on

Not so elegant, I know, but I didn't have enough globals to remember LED positions for all 20 tracks and didn't have the appetite for trying a bit mapped solution.

I think the problem may stem both from the fact that messages are sent back to the APC repeatedly during scrubbing (127 times for each stroke up and another 127 times for each stroke down).  as well as from our original conjecture  - that it might be due to the fact that the APC fader is moving while it is receiving LED related MIDI.

The solution seems to be:

  • MT Pro Input from AKAI APC track volume fader:                     B1 pp qq
  • Response from MT Pro (output to Live track volume fader):    B1 pp qq
  •                               and
  • Response from MT Pro:                                                       Timer 1 OUT (initial delay 20ms)
  • Response when Timer 1 elapses            (out to APC)
  • —  90 52 00 90 53 00 90 54 00 90 55 00 90 56 00 90 57 00 90 58 00 90 59 00 90 ss 01
  • —  Where ss is the LED I want to turn on.  All LEDs are turned off before turning ss on

The timer only produces output to the LEDs once (if the fader is moved fairly quickly) or just a few times for a typical, slower,  movement of the fader.  I think both of you had pointed out to me that the MIDI stream would be dramatically reduced… and it is.

The same fader movement produces several other outputs, some of which sent LED messages to the APC’s.  I’ve taken steps to throttle the MIDI flow there too.

Anyway, I’ve rewritten the code for one of the APCs and it seems to be preventing freezing.  I’ll test more extensively tomorrow, and if it really does work, I’ll rewrite for all 8 APCs and let you know how it goes.

Thanks,

Gabriel

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Posted by (Forum: 51, Answers: 211)
April 28, 2018 9:55 am

crossing my fingers!

( at April 28, 2018 2:48 pm)

Funny…. I almost used that exact phrase in my posting!

( at April 28, 2018 11:50 pm)
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Private answer

GOT IT!!!!

Thanks for all the help.

The problem seems to have been that the APC Mini can’t handle MIDI data updating its LEDs if it comes too quickly.  I was trying to send that data to the Mini at speeds that could exceed 40,000 Bytes per second if I grabbed 7 or 8 faders and quickly slid them down to attenuate volumes or effects.  This easily over-ran the MIDI top speed of 3125 Bytes per second), so I presume that the Mini was receiving data at about that top speed.

There seems to be no provision in the APC for that situation, probably because it would never occur if used directly with Ableton Live (its intended use).  Live couldn’t spit out that much MIDI data by itself. So I guess is that the input buffer provided in the Mini is tiny.

The solution was to stagger the feedback to the APC Mini’s.  The speed at which the LEDs update is not an issue.  LED state just told me what clip was playing or what VST effect was active.  So… I now use a timer for each of the 72 faders on the 8 APC Mini’s.  If a fader is moved, it starts the timer, which has a period of 30ms.  When the timer elapses it triggers the LED output messages going to the Mini’s.  The data is sent in bursts of about 10 instructions each time the timer elapses (so 30 bytes).  Additionally, the timer resets itself constantly throughout the motion of a fader because the fader output is happens more frequently than every 30ms.  So the APC actually might not receive any LED messages until the faders reach their final destination… and then only one burst of 10 messages.

Meanwhile, the MIDI messages going to Live (and not to the APCs) is sent without this kind of gating, so musicality is not effected by delays in reaction.

I also eliminated some of the LED messages upon rethinking my strategy for LED updates.  The number of messages per increment of the fader movement was originally 18.  Now it’s 10, with no real loss in functionality.

I’m so relieved.  And my trust in MT Pro has once again been bolstered.  What a great tool, and what amazing support.  I can finally turn my attention to playing music.  It’s been a long road to developing my system, but it wouldn’t have been possible without MT.  And that’s not an exaggeration.

Thanks,

Gabriel

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Posted by (Forum: 51, Answers: 211)
May 1, 2018 1:45 am

Hi Gabriel,

I’m so glad you were able to workaround the problem with the APC MINI. You have quite a large project. I don’t think I’ve ever seen one so large and complex. I’m glad the Bome and MIDIBuddy software could help. I agree, Bome MT Pro is the greatest. Can’t wait to see version 2 when it comes out. Hopefully, me helping out here will help Florian focus more on new product development. I’m so happy to be here!

Take care,

Steve

( at May 1, 2018 4:43 am)

Hi Steve,
LOL… Probably the reason that you’ve never seen such a large, complex project is that anyone crazy enough to create it would probably have a lot more programming chops than I do – so they wouldn’t be asking for help on the forum.
Everything still seems to be running reliably now … one day later. So, thanks again for the advice.
BTW, MIDIBuddy is certainly the icing on the cake. I use it mainly to link a trackball to the Beat Repeat effect in Live.
Bye for now,
Gabriel

( at May 2, 2018 12:04 am)