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Level 2

216 points

Lousy iMovie HD 6.0.2 playback -- stuttering video and audio

I've spent several weeks now working on a movie which I'm aiming to be about an hour long. Using iMovie HD 6.0.2, QuickTime Player 7.1, OSX 10.4.6 ...all the latest versions, it seems, on a G5 1.8GHz SP, with 1 GB of RAM and two internal drives (System on 80G, movie project on 300G Maxtor drive with lots of room to spare). Before starting iMovie, I close all other applications and relaunch the Finder to have things "clean" as possible. All external drives are shut off. Still....

...the playback quality is becoming so bad, I'm concerned that I won't be able to continue this project using iMovie. The sound is poor, the moving slider is jerky, the image is skippy as is the sound. Mouse actions are slow to respond, and I'm sick of seeing the rotating beachball.

What is wrong with this software??? _ I never had this problem with older versions of iMovie (e.g. version 3), with equally-large projects, on a slower machine (G4/450 with less memory and smaller drives).

If I complete it, will it still stutter once it's burned onto DVD using iDVD 6.0.2? __

Is this a plot to coerce users to buy the pricier Final Cut Pro Express? ____ (is FCPE immune from this problem? _)

The current situation is very bad. Is there a fix? ___

G5/1.8GHz SP 80GB Mac OS X (10.4.5) 1GB RAM, +300G internal, 4 external FW HD's

Posted on May 25, 2006 12:15 AM

151 replies

May 28, 2006 9:53 AM in response to F. Farmer

My guess is these slowdown/stutter problems are related to the project's audio, not the video or the project length. And that the likelihood increases after extracting audio, importing certain types of music from iTunes, Copying and Pasting audio, etcetera. The more complex the audio is, the more likely the problem is to occur.

Without intending to, it's pretty easy to create an audio rats nest in iMovie that might be present quite a challenge. If either QuickTime or iMovie has an audio vulnerability, they might be overwhelmed.

One solution that has helped others is to convert songs to AIFF files instead of importing direct from iTunes, where songs may use a variety of formats. Use iTunes to burn an audio CD of the songs you want to use in the project, then drag the songs from the CD to iMovie. They arrive as AIFF files, iMovie's native format.

Another solution that seems to work is to "flatten" the audio by exporting the project audio to an AIFF file, then import THAT file back into the project, replacing the audio that's there. Best done, for ease of editing, when the project is virtually complete.

The odds for problems seem to increased substantially when QuickTime 7 was introduced, so I suspect this may be a QuickTime problem, not necessarily an iMovie problem. Or, quite possible, a combination.

I suspect one's editing style makes a difference. Users who create complex audio may need to invoke workarounds to keep things running smoothly.

Hope something here helps. Wish we could discover the root cause of the problem.

Karl

May 28, 2006 10:35 AM in response to Karl Petersen

Wish we could discover the root cause of the problem.

I'd sure like to examine a few projects that have this problem. I've never been able to reproduce the slowdown/stutter here, no matter what kind of project I build to try to make it happen.

Trouble is, iMovie projects are way too large to email to each other, and most projects won't fit on a DVD (burned as a data file, not encoded by iDVD). Twenty minutes — or 4.6B — is about the project limit for a DVD.

If there are readers of this thread who see the problem on a project small enough to burn on a DVD as a data file, I'd sure welcome your sending it to me. I've written some software to examine the innards of an iMovie project file. With luck, perhaps it could be tweaked, based on what I see in your project, to discover something useful.

If nothing else, if your project plays okay here, that's important to know too.

If you are willing to share it with me, click on my name at the left to get my email address. Ask me for my postal address. (I'm in the U.S.)

When I've received all the projects I need, I'll post another message to this topic.

Karl

F. Farmer Author

Level 2

216 points

May 28, 2006 2:41 PM in response to Karl Petersen

Thanks for the tips, Karl

I'll try the AIFF suggestion, and let you know if it makes a difference. My project is too big (55 minutes) to send to you, but I see that others are having similar problems with projects that are only a few minutes long. Hopefully they'll send theirs to you.

G5/1.8GHz SP 80GB Mac OS X (10.4.6) 1GB RAM, +300G internal, 5 external FW HD's

F. Farmer Author

Level 2

216 points

May 28, 2006 2:45 PM in response to Bizguru

Bizguru,

Take a look at Karl Petersen's messages below (or above??), especially the second one where he offers hands-on assistance for someone working on a small project. Sounds to me like your project is the perfect size that he could look at.
Thanks-

Mini Don

Level 1

2 points

May 28, 2006 4:03 PM in response to F. Farmer

Karl,
I think you ideas about length and modified audio being factors are correct. I have one I'm working on now that started having problems when I got it up to about 40 minutes. I still am not done with it because I have so much trouble working with it. I have extracted audio and moved it to other areas of the time line but have added no music up to this time.

I have another I started and have completed except adding the music track. It is only about 12 minutes long but I have no problems with it. I have also extracted and moved audio on the time line.

I have no plug ins in my system.

Don Ross

F. Farmer Author

Level 2

216 points

May 28, 2006 6:45 PM in response to Karl Petersen

Karl,

I checked my audio clips and found they were already AIFF except for one. So I went back to iTunes, and converted it to AIFF then reimported it into my iMovie to replace the original clip. I also trimmed a number of overlapping audio clips to eliminate the overlap. I still kept several overlaps as they occur where I've put a cross-dissolve and I want one sound to fade out as the other fades in.

Result = a very slight improvement (I think!). It still stutters and jerks etc. but not as hopelessly bad as before. (By the way, I duplicated my project and did these experiments with the copy, as I didn't want to completely muck up the original movie, bad as it is). I then emptied the iMovie trash, in case that baggage was dragging it down. Made no difference. Still stutters, even after saving and restarting. No other applications running while I work on iMovie.

So you may be onto something with the audio causing the problem.

My movie has about six music pieces varying in length from about 3 minutes to 9 minutes each. These are for background music, and at times 'feature' music (replacing the video clip's own sound) -- I try to sync the imagery with the music rythym ...which is impossible to do when it's behaving in such an erratic manner.

I'm not sure what to try next, other than eliminating each music track one-at-a-time to see if I can get to a point where there's no more stuttering. (I could try this on this copy of my movie).

AIFF is uncompressed music. I wonder if a compressed format (like MP3 or AAC) would work better, by taking up less physical space in the project). Thoughts on that? ___

G5/1.8GHz SP 80GB Mac OS X (10.4.6) 1GB RAM, +300G internal, 5 external FW HD's

F. Farmer Author

Level 2

216 points

May 29, 2006 1:18 AM in response to Karl Petersen

Since my last message, I created a second copy of my project so I could experiment with it. One by one, I deleted each music track (all AIFF formats) I had added, and emptied the iMovie trash. I even saved and closed iMovie, relaunched Finder and reopened iMovie.

Result. No better. Even with 11 music pieces removed and deleted (totalling over twenty minutes in time), it made no difference. Playing back the movie still stuttered and jerked.

I suppose the next step is to delete each of the audio clips that were extracted from the video, one by one.

Maybe the problem doesn't 'correct itself' by backtracking. I've spent several weeks building this movie, I don't want to start over from scratch with no guarantee it'll be OK.

This is very discouraging....

F. Farmer Author

Level 2

216 points

May 29, 2006 2:23 AM in response to Karl Petersen

At last, some IMPROVEMENT....!

Further to my last message, I deleted 17 audio clips that I had extracted from their corresponding video clips. I did not empty trash this time.
Result: considerable improvement (about 80% better) but still some occasional stuttering. Undoing these deletions just brought back the bad stuttering. Back to the trash they went.

Then I deleted another 13 extracted-audio clips. I still did not empty trash.
Result: almost perfect

Certainly very workable now. Virtually no stutter.

Next, I decided to bring back in a music soundtrack from iTunes. But instead of AIFF format, I first converted it to MP3 then imported it to iMovie. It was almost 3 minutes long.
Result: no problem. Still very smooth!

Finally, I brought in a second music track from iTunes (also MP3, almost 10 minutes long).
Result: Still very smooth!! I'm excited! However, I still have to deal with those extracted-audio clips that are sitting in Trash. I will want to reinstate them at some point. And I've got several more music tracks to import.

CONCLUSION (for today): Perhaps the problem is with audio clips that have been extracted from the video. To those of you who are experiencing this stuttering problem... DO YOU HAVE ANY EXTRACTED-AUDIO CLIPS IN YOUR MOVIE? __

I've been at this for about 14 hours today. Long enough. Time for bed.
Stay tuned.... Fingers crossed.

G5/1.8GHz SP 80GB Mac OS X (10.4.6) 1GB RAM, +300G internal, 5 external FW HD's

May 29, 2006 10:46 AM in response to F. Farmer

Thanks for your detailed reports. Very interesting.

In one, you said:

I checked my audio clips and found they were already AIFF except for one.

Not sure I understand you there. Did you find the AIFF audio clips in the Media folder, or find that your iTunes music files were AIFFs? (iTunes lets us import music to iTunes as AIFFs.)

It's normal for iMovie HD to convert iTunes music files to AIFFs as our songs are imported to iMovie HD, so a Media folder would normally contain those AIFFs. At least one user found, however, that replacing her iMovie-created AIFFs imported from iTunes with AIFFs imported from an Audio CD solved her playback problem. Something was different about those AIFFs.

So although the audio files in the Media folder are AIFFs they may not work as well as AIFFs imported from an Audio CD. That's not to say they are causing your playback problem, they don't seem to be. But I suspect they can SOMETIMES cause a problem.

(The maddening thing about this playback problem is that there seems be multiple contributing factors, sometimes working together and sometimes independently.)

About the extracted audio. If lots of extracted audio clips can contribute to playback problems, which I suspect they do, that may be related to HOW iMovie does it. When iMovie extracts audio from a clip it duplicates the audio from the clip's ENTIRE Media file, then mutes the audio of the selected video clip. So if a Media file contains a 30-minute scene, and we split the 30 minute clip into two clips, one 1-minute clip and one 29-minute clip, extracting audio from the 1-minute clip extracts 30 minutes of audio.

More typical, let's say we split the 30 minute clip into 10 clips, each 3 minutes long, then extract audio from each of the clips. Now the project will contain 10 AIFF files, each 30 minutes long. When playing the project iMovie must open and close numerous AIFF files and juggle which part of each file to play. And, quite possibly, adjust the volume while doing it.

I'm quite certain QuickTime/iMovie is theoretically able to do that, but if there's some factor affecting efficiency, it might not do it smoothly. (A slow disk, or full disk, or a permissions problem might cause inefficiencies, for example.)

It might be more efficient to extract the audio of the entire 30-minute clip just once, THEN do the necessary clip-splitting. If we split a clip, then without moving the playhead split the extracted audio clip below it, then Lock the audio clip, it will stick to the video clip as we drag the clip elsewhere on the Timeline. That will reduce the number of extracted audio files, which MAY simplify iMovie playback. It may be possible to have our extracted cake and eat it too.

If it's not all too obvious, this is all speculation for I've never had a playback problem here to test. Acquiring a few troubled projects may help end my endless speculation. 🙂

Karl

F. Farmer Author

Level 2

216 points

May 29, 2006 11:35 PM in response to Karl Petersen

By Control+clicking (like 'right-clicking') the music audio track in the bottom track of the Timeline, and selecting Get Info from the pop up menu, it showed whether that track was AIFF or not. The one that wasn't, was '.m4p' which I think iTunes assigns to AAC or protected AAC format tracks. (Since AAC seems to be an iTunes/Apple standard, I'm surprised they haven't made it the iMovie standard too. Perhaps just as well they didn't, if it's too propriaty -- unique only to Apple?).

iMovie also accepts MP3 formats which are compressed and take less room than AIFF. So I've decided to reintroduce all my music tracks in MP3 format to iMovie. Hopefully that will 'lighten' iMovie's burden. In theory, anyway!

Interesting that AIFF tracks imported from a CD to iMovie caused less problems than AIFF's from iTunes. Something else to keep in mind.

As for the extracted audio, most of my clips were created when I first loaded the video in from the camcorder. iMovie automatically split the stream into individual clips. I presume what you're referring to, is when one takes one of these clips and splits it 'manually', then extracts the audio from one or more of the clip's fragments, and gets the entire clip's audio each time, not just the fragment's audio. It doesn't appear as such in the Timeline. It appears as if you get only the audio for that clip fragment that was selected when the Extract Audio command was executed. If the entire clip's audio is extracted, then much of it must be hidden from view.

I take it that it would be better to extract the audio from a clip BEFORE splitting the video clip. Then split the audio clip afterwards to match the corresponding fragments of the video clip. I try this in future.

I've still got to reintroduce several music tracks back into my movie, but I'll make them all MP3. I'll do these first, to see what happens, before I start recreating the extracted audio clips that have been deleted. Don't worry, I'll report back any results!

G5/1.8GHz SP 80GB Mac OS X (10.4.6) 1GB RAM, +300G internal, 5 external FW HD's

May 30, 2006 12:22 AM in response to F. Farmer

The .m4p audio files you mentioned are probably protected songs purchased at Apple's iTunes site. They are not converted to AIFFs when imported to iMovie.

To the best of my knowledge, all other audio files are converted to AIFFs as they are imported to iMovie.

I presume what you're referring to, is when one takes one of these clips
and splits it 'manually', then extracts the audio from one or more of the
clip's fragments, and gets the entire clip's audio each time, not just the
fragment's audio.

That's correct. I'm referring to clips that we split manually.

It doesn't appear as such in the Timeline.

As one would expect, the extracted audio clip matches the length of the split video clip. But the actual Media file may be considerably longer. To check its size, look in the Media folder of the project. (Be careful, the Finder window sometimes has to be closed, then re-opened to show you the correct file size.) Or tell iMovie to revert the audio clip to its original state. That should display its actual length. (Untested.)

Karl

Karl

F. Farmer Author

Level 2

216 points

May 30, 2006 12:46 AM in response to Karl Petersen

Karl,

You're right! The .m4p file was one purchased in iTunes. And all those I converted to MP3 in iTunes have all been automatically converted back to AIFF in iMovie6, so it was probably a waste of time to convert to MP3 in the first place.

The GOOD NEWS is: I've re-imported all six music audio tracks (MP3, now AIFF) into my movie, and iMovie plays back perfectly. No stutter, instant stopping, etc. Beautiful. Now, the big test will be dealing with the extracted audio clips, still sitting in trash. I wonder if I can export them to an external folder, burn them onto a CD-RW and then re-import to iMovie from the CD? Sounds convoluted, but if it works, what the heck. I'm now convinced the stutter problem is to do with extracted audio clips.

In iMovie3 (which I used before), I used to see a media folder (that contained all the original clips and transitions) and a Quicktime movie file in my movie's folder. Now, with iMovie6 I don't see either -- it just contains one file with the star icon. I presume this is to keep meddling fingers from mucking up the the contents of the media folder. So is the media folder a hidden file? ____ Is there a QT file somewhere? ___

F. Farmer Author

Level 2

216 points

May 30, 2006 1:28 AM in response to F. Farmer

Oh oh...

Before recreating the extracted audio clips, I decided to do volume adjustments to the music clips I had just added (see above), and make them the same as before. I opened the 'original' version of my movie (called 'V1') and adjusted the windows so I could easily compare it with my new test version ('V2'), then made some volume (sound level) adjustments in V2 to match V1. i.e. I had both versions open at the same time.

Of course, when playing back V1, lots of stutter (it still has all the extracted audio clips in there). I expected that. But when playing back V2 (while both versions were open) I began to experience a little stutter in it. I presume it was because of having both version open together (hogging resources). Still, it was workable, so I did some volume adjustments to the first two music tracks in V2.

After closing V1, V2 played back quite well, but I detected just a hint of possible stutter and occasional buzzy/staticy sound. Still workable, but I'm nervous now ...I've still got lots to do in this movie and I hate to see the problem re-emerging at this point.

Must quit for now. Will report back tomorrow.

jacqo

Level 1

0 points

May 30, 2006 5:17 AM in response to F. Farmer

Hi.
I experienced the same problem,but it occured only after I combined two projects.(See my post "can you repair iM projects)
I filmed a concert of a local band and wanted to make a dvd for the players.
I first wanted to make a double dvd,because of the total length.
Dvd 1;before the concert and part one of the concert.
Dvd 2;part two of the concert and what happens after.
Both ran without problems.I used the equalizer to boost the sound a little.
Some of the players wanted just the registration of the concert,so I copied a part of project 1 into project two and deleted the last part of project 2,to have the whole concert in one project.
This when the missery started.
Both the original part one,as the new project run very poorly now.
They are almost impossible to work with,and even can't burn them with iDVD.
Even deleting the extracted audio doesn't help.
I wanted to export the project to QT but that takes at least two days,so that's no real option.
I think that Apple should come quickly with a solution,to many people having problems with iM6

Jacqo

gl0ve

Level 1

0 points

May 30, 2006 6:42 AM in response to F. Farmer

today i had a great first session with imovie
went through the online tutorials
opened iMovie5 on my G4 laptop
created a new project
began importing clips
it was all going so well.....

once i had about 10 clips
AVI's imported from digital still camera
each clip approx 10MB

the video got all choppy and then stopped playing completely

i installed the latest Quicktime (from 7 to 7.1.0)but this made no difference

i removed half the clips (deleted) and still no change

my internal 60GIG HD has only 9GIG free space>i have just added a 300 ext HD but am not sure what is safe to transfer over and what should remain on the internal HD

any and all suggestions appreciated>>

G4PowerPC Laptop>1Gig SDram> Mac OS X (10.3.9) Lacie d2 Extreme 300 ext HD>Lacie ext d2 DVD burner

Lousy iMovie HD 6.0.2 playback -- stuttering video and audio