Troubleshooting iMovie/iDVD: Splitting movies to prevent buffer underrun error

We've previously reported on a problem with buffer underrun in iMovie projects burned with iDVD that seems to arise with some (usually long) movies.

MacFixIt reader Al Skerker suggests that there is a correlation between the complexity (not the length or size) of an iMovie project and the occurrence of buffer underrun errors when trying to burn an iDVD project (iLife4).

"A simple fix will avoid this condition and dramatically reduce the time it takes for Stage 4 (Multiplexing and Burn) iDVD processing.

"The iMovie/iDVD project that succeeded was 55 minutes long and occupied 17.06 GB of iMovie project files. I made two DVDs from this iMovie project, altering the iDVD theme and both burned properly. The iMovie/DVD project that failed was 41 minutes long and occupied 9.43 GB of iMovie project files. The longer iMovie had 12 waveform files and 106 media files (clips, effects, titles, stills etc.). The shorter iMovie project, the one that failed to burn (on each of three tries), had 67 waveform files and 175 media files; consequently, the shorter iMovie had a substantially more complex structure."

So Skerker simplified the movie by splitting it into 9 contiguous .dv files, which allows iMovie to view 9 simple objects rather than the various waveform and media files. The result was success in iDVD burning:

"I first rendered the shorter iMovie project into a set of full resolution .dv files using the iMovie QuickTime share option. I chose to render the movie into 9 contiguous .dv files, reasoning that it would be easier to import smaller dv files. I opened a new iMovie project, imported the 9 clips into the timeline and proceeded to add chapters and prepare an iDVD project (with two additional stills). The new iMovie project had only 9 media files and no audio waveform files since the audio was rendered by iMovie into the dv file. The resulting iDVD project burned flawlessly. The times for the various iDVD stages: Stage 2: 11 minutes, Stage 3: 1 hour 58 minutes, Stage 4: 10 minutes. The Stage 4 processing time astounded me because even the DVD that previously burned properly took at least 80 minutes for the Multiplex and Burn stage to complete and well over three hours for all stages combined."

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