Eternal External Sync Problem

[Gurulogic]

Yeah, the Abes really gotta hire themselvelves a midi clock guru..
The issues I've had, it almost seems as though Live takes over so many resources for a a split second with certain actions (ie:dumping a huge volume of midi CC's to the mix parameters) that it starves the midi interface from receiving the proper data.Some of my gear puts up with it some of it doesn't. The rest of the time everything is fine.I could swear Live makes my midi interfaces skip a beat and it's not Live's clock that's faulty at all, but something else.

[bynoe]

Yep it syncs horribly with my MPC 1000. I'm beta testing 8 and its got worse. When i hit play the MPC plays the first few beats really quick then settles down. its bizarre. Must report this.

[pmestrez]

Hello All,

I can easilly understand that a midi interface with its buffers, own thread priority, IRQ management, driver code quality, latency etc...) is not something that ableton can manage easily. They don't have to do so in fact.
So i'm not completly agree to say Ableton is the only faulty about this topic.

I can understand that all these midi interface technical stuff may introduce a latency.
Ableton has just to provide a dedicated midi sync clock compensation for each midi out port.
In addition, it is important to ensure that when the latency compensation has been find, the midi clock must stay steady and doesn't drift. That is for me up to the abletonian !

They can at least try to do that and ensure the threads/process that manage midi clock out are set to highest priority.
for me, the windows GUI refresh can even slowdown (sorry for those who don't like that) but the midi clock timing NEEDS to stay tight and constant.
"It is just" a matter of priority and scheduling policies.

Regards,

Pierre.

[broc]

"It is just" a matter of priority and scheduling policies.

Absolutely. But I think that application programs like Live don't have much control over thread management and priorities. So the basic problem is that we have to deal with general purpose operating systems which are not designed for real time operations as needed with MIDI and audio.

Personally, I've noticed (on OS X) that synchronization with MIDI clock or MTC works very well provided the CPU load is constantly less than 50%.

[pmestrez]

Yes.

While it could be difficult to change scheduler/dispatcher policies of OS.
Things like set a higher affinity and thread priority could be done on the threads that manage midi.
Maybe time quota itself by regestering aaplication differently on the OS... Don't know. Microsft is not open to that kind of stuff.
In addition, having 2 seperated thread: one that manage notes/CC (linked to the GUI) and another that only manage midi clock tick maybe...
Yes, they would write to the same output but the 2 thread could add something better... don't know... only supposition of an old (no more) c++ coder

Regards,

Pierre

[aqua_tek]

Personally, I've noticed (on OS X) that synchronization with MIDI clock or MTC works very well provided the CPU load is constantly less than 50%.

Guess it varies from person to person. I'm on OS X as well, and even on a simple project, with just a couple of tracks, CPU well below the 50%... all the way down to the teens, the midi clock on live continues to be problematic.

[Tone Deft]

sync has never failed me when playback is stopped, in that state it's rock solid, better than Pro Fools.

[broc]

Personally, I've noticed (on OS X) that synchronization with MIDI clock or MTC works very well provided the CPU load is constantly less than 50%.

Guess it varies from person to person. I'm on OS X as well, and even on a simple project, with just a couple of tracks, CPU well below the 50%... all the way down to the teens, the midi clock on live continues to be problematic.

Well, even if you have an avarage CPU load of 10% you may get peaks over 50% when doing some operations like eg. opening a window. So what I meant with "constantly less than 50%" was that such peaks don't happen. In other words, pure playback without touching anything. I understand it's a serious limitation but just wanted to point out that timing problems may be due to interference with other operations controlled by the operating system.

[si.]

This is a headache alright... I ended up giving up an it altogether! Just set the bpms equal and hit play simultaneously, then nudge my drum machine into sync...

Would be great to have this sorted for live 8...