MIDI vs USB connection for midi controllers

[motidave]

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Do these types of Midi-to-USB converter cables work if, for example the synth is 5-pin only ports and you want to connect to USB (or USB hub)? problems with latency, jitter or other ... ?

there's lots of versions of these ...

http://www.amazon.com/SANOXY-Keyboard-I ... +converter (https://www.amazon.com/dp//ref=nosim?tag=kvraudio-20)

http://www.amazon.com/Neewer-Music-Keyb ... +converter (https://www.amazon.com/dp//ref=nosim?tag=kvraudio-20)

[theEmbark]

Generally speaking yes. What are you trying to hook up?

But yes you will probably see latency and jitter issues. If you can swing it an interface is really the way to go. If you're in a pinch this will get you by.

[JCJR]

Do these types of Midi-to-USB converter cables work if, for example the synth is 5-pin only ports and you want to connect to USB (or USB hub)? problems with latency, jitter or other ... ?

there's lots of versions of these ...

http://www.amazon.com/SANOXY-Keyboard-I ... +converter

http://www.amazon.com/Neewer-Music-Keyb ... +converter

Hi motidave

I have never used one of that type. That generic very-inexpensive type came on the market a few years back. The company I retired from a few years ago, tech support tested some models which looked like that, same low price. Tech support said they worked good, but dunno how seriously they tortured the units. That is such a generic item maybe some are good and some are not. Dunno. The price is certainly right.

They probably have a small circuit board with a pic chip or something similar in that little nodule, which does the usb/midi conversion. You don't need a supercomputer to do midi to usb conversion, but requires at least a little bit of processing power to have enough smarts to do the job. Because USB and MIDI are completely different. No "simple" way to do it except using some kind of little processor. Can't do it with just wiring tricks and a couple of logic chips. So far as I know.

Which in principle is not drastically different than you would find in the slightly bigger, slightly more expensive single port midi interfaces that have been sold for decades.

Fer instance MAudio has been making the MidiSport for a very long time, which is almost as small as the nodule in the cables you linked--

http://www.m-audio.com/products/view/mi ... sY94I-cFi4

I've used MAudio MidiSports for software testing, both the early serial ones and the later USB models, and never noticed them acting sub-standard, but was just testing with it, not putting it to heavy work.

Back in the 1980's I worked with a company that made serial midi interfaces (usb hadn't been invented yet). Some of them were in metal boxes a little bigger than a midisport, but one model was barely bigger than those usb cables, just a little plastic tube with some midi and serial ports sprouting out of it.

[justin3am]

They probably have a small circuit board with a pic chip or something similar in that little nodule, which does the usb/midi conversion.

Maybe not even that. Many simple USB/MIDI interfaces use an off-the-shelf USB/MIDI chip from vendors like Holtek.

I used to work for M-Audio, when they were part of AVID. I was working in QA when the 20th anniversary edition of the MIDISport interfaces were released. We did a lot of comparisons with other USB MIDI devices and found that it was really common for the cheaper interfaces to lose data when transmitting large amounts of Sysex data at moderate speeds. Most USB MIDI interfaces will have jitter issues because they use a bulk data transfer method which falls apart when timing is critical. I don't know much about the technical details, so I'll refrain from talking out of my ass any more than I have.

I know that there are some companies who used their own kernel drivers to get around this issue (maybe Emagic) but at the cost of losing compatibility with the USB MIDI class drivers. I think only Roland are doing that these days, specifically with their SBX-1.

So far MIDI over ethernet appears to suffer less from jitter than USB MIDI but it's still not perfect.

[JCJR]

Thanks justin3am. Wow, didn't even know dedicated USB/MIDI chips are available.

I ought to read about midi over ethernet sometime, am ignorant of it.

So most class-compliant USB midi interfaces, even expensive ones, might be jittery? Because of the transfer mode?

In the old days computer midi jitter could happen because the driver could get "held off" for a variable amount of time before delivering the data to the midi program (or transmitting data received by the program). In those days some low-level processes would lock out interrupts while doing their work, and sometimes would lock everything else out for fairly lengthy periods. If midi needed sending or receiving when other processes had things locked down, the MIDI driver just had to wait until the interrupts were enabled again.

Wonder if the obligatory single port of MIDI that gets included on so many audio interfaces are class-compliant? IOW, if an interface with custom audio driver would have custom midi driver as well, or just make the midi part class-compliant?

I wonder about midi jitter on firewire or thunderbolt audio/midi interfaces?

[justin3am]

In the old days computer midi jitter could happen because the driver could get "held off" for a variable amount of time before delivering the data to the midi program (or transmitting data received by the program). In those days some low-level processes would lock out interrupts while doing their work, and sometimes would lock everything else out for fairly lengthy periods. If midi needed sending or receiving when other processes had things locked down, the MIDI driver just had to wait until the interrupts were enabled again.

Yes, that is the situation as I understand it but again, my knowledge of this stuff is pretty basic. However, I also don't want to overstate the issue. Unless a super steady MIDI clock source is needed, or you're really looking for a problem, most people won't notice this kind of jitter.

Wonder if the obligatory single port of MIDI that gets included on so many audio interfaces are class-compliant? IOW, if an interface with custom audio driver would have custom midi driver as well, or just make the midi part class-compliant?

I wonder about midi jitter on firewire or thunderbolt audio/midi interfaces?

I can only tell you based on observations I've made during test analysis... I'm learning about the engineering side of this stuff but really I don't have much experience. I wouldn't want to start talking about driver architecture...

When I was doing jitter tests, I found that you'll get poorer performance when a MIDI interface and an audio interface are sharing the same USB root hub. This seems to be true if they are in the same box or in different boxes, if you know what I mean. I can't say that for every product out there but it seemed to be the case more often than not. I don't have a lot of experience testing FireWire Audio/MIDI Interfaces but I can tell you that the MIDI ports on my MOTU 828mk3, M-Audio Project Mix I/O and Profire 610 all have pretty bad jitter. I wouldn't use them to sync anything but they're okay for recording 1 channel worth of notes without much controller data.

I think the best case scenario, is a dedicated USB MIDI interface connected to a USB port which isn't sharing resources with other ports. Probably unrealistic.

It's been a while since I was running these tests, so I don't have concrete numbers. You can find a lot of useful information here:
http://www.kvraudio.com/forum/viewtopic ... 1&t=373069 (research done by KVR member mkdr)
http://www.innerclocksystems.com/New%20 ... itmus.html (MIDI clock and sequencers)
http://www.e-rm.de/data/ERM_Jitter_Report_02_14_EN.pdf (more about MIDI clock)

[JCJR]

Thanks very much Justin for the great information and links!