@charl said:

I would just like to point out that in some cases it may be your drives that might be touching their limits and giving you audio quircks. Upon 'live' playing, the system clearly has less flexibility to organise resources than upon 'sequenced playback'...

Also maybe Logic is the cause of your 'real time" quircks.
In Logic, there is clearly a difference between real time playing and sequence playback !!!
It would be interesting if you tested the VI in an external host and play the notes on a midi instrument in Logic connected vie iacbus to the VI host.. If you got the same problem on 'live' playing it would indicate that it is not Logic.

Also, bare in mind that OSX has the ability to re-organize resources to better achieve a task that it may have only partially achieved at a previous trial. Evan Evans wrote some very interesting thoughts on this last year...
He told of how, at 3rd or fourth playback, some exs instruments were running fine while at first playback the audio was full of hiccups.
I'm not saying it's totally connected to your problem, but it's worth knowing about it...

One last side issue worth knowing about (I donno if it has been corrected since Logic 7.2) is that in some cases, when Logic has hit a CPU limit, and has given you the alert message... You may find that it will repetitively give you that same message at 'given' point in the arrange, even though you've changed the arrangement and playback should run fine.
Usually this happens at entry point of a sequence. Clearly this is a bug !!! Logic has no reason to give you the 'CPU maxed' message.
There is one simple way to bring back Logic to normal : Nudge 1 or a few sequences (with start point at problematic position) back & forth a bar.

You might run into this problem if you're having CPU issues, so I thought this might be a useful tip.

Just a few thoughts...

Charl

Excellent Post.

This is a reality that, for me, goes on day after day.
After entering a few tracks in a full orchestral arrangement, it takes logic 3 or 4 playbacks to 'straighten out'. As i use only a laptop, and push the limits constantly, this is something i'm used to. Freezing tracks helps, but if i'm writing a robust passage, then i will get meesage of of CPU overload, and as you rightly point out Charl, shifting the playback point a bar or two frees up the system again, the messages dissipate.
It's interesting to note that Logic seems to 'learn' fairly quickly. Once a full passage is set, if i add a track, the activity monitor shows the previous audio load, plus an added percentage for the new track. When i playback the updated passage two or three times, the audio load reduces to just above the previous setting. (I should say this is with EXS. A clever tool, and i mourn the fact this sampler isn't sold in standalone format anymore. Apple would make a fortune if they did this, i'm sure.)
Even on my little laptop (G4,867mhz,512mg ram, 5400rpm HD), i can, with care and patience, load upwards of 80 tracks of instrument articulations, playing back each new 'total' until the audio comes clean, then adding another track. It's not perfect, but the work gets done. I still have to freeze tracks occasionally, but in general my little rig get's to the end of some fairly hefty arrangements unscathed, after the compromises mentioned.
I'm about to add an external HD (7200rpm), and i think this will reduce the instances of audio 'glitch' even further.

I think some of the discussion about the VI's and overloading symptoms stems from the assumption that live playback first time should be perfect, each and every time.
Logic, and other programs too, don't do this even with a smaller library (Just my example and experience). I'm not sure how many work as i do, playing back a passage over and over again, fine tuning and modifying, but it's a routine that i use, that i virtually ignore the first one or two playbacks, until Logic learns what to play, and when.

Good post Charl, and a timely reminder that more than one cause is possible for a symptom.


Alex.

@hermitage59 said:

Freezing tracks helps, but if i'm writing a robust passage, then i will get meesage of of CPU overload, and as you rightly point out Charl, shifting the playback point a bar or two frees up the system again, the messages dissipate.
Alex.

That's a slightly different thing you're mentioning here.. But it's solution number one in the list.
If you're however continuously getting the overload message at a specific point and yet have no reason to... i'm actually suggesting to move the SEQUENCE(S) back and forth a bar... I usually do that with a shortcut. Curiously it seems to clarifie the 'corrupted' info that's deceiving Logic into believing it has too much to process at that point..

chari,

Your insights into disk-streaming have made things clearer to me.....I did not realise that any disk-streaming was happening with VIs.....i thought the samples resided in RAM once loaded and that was that.....

Maybe you could help me just a little more, and tell me what the fastest "HardDrive" sytem is....and how to set it up for the best possible performance.

Thanx so much,

SvK

@charl said:

Also maybe Logic is the cause of your 'real time" quircks.
In Logic, there is clearly a difference between real time playing and sequence playback !!!
It would be interesting if you tested the VI in an external host and play the notes on a midi instrument in Logic connected vie iacbus to the VI host.. If you got the same problem on 'live' playing it would indicate that it is not Logic.

Charl

Chari audio cuts out from live-playing in other hosts such as Plogue as well (when selecting multiple VIs simultaneously)

SvK

I don't now much about drives apart from this..
- The more RPM 'rounds per minute' the better. Some drives are faster than others.
- Keep in mind that some data paths are wider than others. Drives connected via firewire have a smaller bandwidth (I think) because of the firewire connection..