screen updating suddenly is slow and jumpy

[Richard Fairbanks]

I am not talking about the GUI freeze.

I have a 90 min film, mixed on PT7.1.3 last December. Now we have reconformed to a new version, about the same length. Using 7.3.1, recent CS, MOJO. I started with my previous session file, inserted 2 hours of silence near the head (to move the old audio to start at 3 hours and open up blank space at 1 hour). Then, using an EDL, cut and paste old audio to the new picture starting at 1 hour. (Software conform was not an option, don't get me started!) There are maybe 120 tracks and auxes, master faders, etc. Anyway, for the most part everything works as it should. After the first round of cut and paste there were many sections of silence in the new version. New audio is to be mixed into them from an omf file and/or effects library, to match the new pictures that were added.

Here's the problem. During a couple of those silent sections (not all of them) the GUI and automation updating suddenly becomes very slow. You can watch the GUI timecode display and at the instant the playback cursor hits the beginning of silence the numbers start updating only about twice per second. Not just the number readout but the entire display and responsiveness to keyboard and mouse commands. This continues until playback hits the next area where I have pasted old audio. At that moment the GUI behaves normally again. A couple of these silent areas are over a minute long and the slow GUI makes it difficult to work within them. I have just finished working on one of them and noticed that the automation is noticeably less accurate (volume, for instance) and editing and scrubbing anywhwere within this area is a nightmare, the system is so slow and sluggish. Highlighting a selection is particularly difficult. Pro Control faders do not jump, though, and recorded automation is not affected as badly.

If I turn off automation the slow GUI is instantly okay. It is a problem related to automation. Adding new material and automation to the area does not make any difference. I have tried manually printing new automation "straight lines" through the affected areas on all tracks, but that makes no difference. This was my attempt to "thin automation" through the slow areas. Now I am at a loss with how to make things right again.

Any ideas?