I had never encountered audio slipping before, but after experiencing it, and in turn, troubleshooting the issue, I understand that it isn't an uncommon problem in Final Cut Pro, which is what I edited this particular project on. Because of the frustration involved with resolving the issue, I thought I'd share the problem and the solution for this particular set of circumstances, in hopes that it might help others who come up against this kind of headache, as a result of similar project missteps.
First off, I was working in Final Cut Pro 7 with 8mm silent films that had been transferred to Apple ProRes 422, 1920 x 1080 files at 16.99 fps. I chose a sequence setting I thought closest to the video, which were the ProRes film transfers, mixed with still images that were hi-rez Tiff files (not over 3000 pixel aspect ratio, as learned from previous experience with the dreaded "General Error" nightmare). The audio consisted of music at 48kHz, 8-bit and narration from multiple sources, recorded on multiple devices. The variety of audio rates ranged from 48kHz to 44.1 to 16 and the file types were .MOV, .WAV and AIFF. Well, I threw those in there as though everyone was going to play nice, without a whisper of protest, and oddly enough, most everyone did.
However, I noticed that each time I exported my Apple ProRes sequence, I experienced drift in the first section of the export (approximately the first 7 minutes or so) and then audio and video would magically fall back into their intended places for the rest of the 38minute piece. When I would play the sequence inside Final Cut, it would play in sync. It seemed to be something happening during the export.
As per usual when I can't troubleshoot on my own in short order, I started asking another editor friend or two, which eventually turned into relentless badgering but most had good humor about it. I also began an increasingly frantic thread search on various forums. Although my fellow editors probably got a little sick of hearing my latest reports of sync failure, and slow decent into madness, I did end up with a few take-aways from both personal editor friends and nice colleagues that contribute to those forums. I found out that some people blame audio slipping on Final Cut and there were a few claims that ProRes can sometimes cause audio drift, but mostly everyone agreed that mixing multiple audio rates in the same timeline is just plain unwise. There were various offered solutions with many different circumstances and particulars, none of which matched mine exactly, but a few that were close. This is what I did ...
I tried different types of exports from Mpeg-4 to various .MOV files with different codecs, to Compressor exports and so on. No export would change the first 7minute out of sync problem. Additionally, I tried:
- Exporting the audio in my sequence as an AIFF at 48kHz and then brought it back in FCP. replaced the previous audio in the timeline with the AIFF file.
- Converted a few of the audio files through Quicktime Pro 7 to AIFF 48kHz individually and replaced the 16 and 44.1KHz files and exported sample sections to see if that made a difference. Nope.
- Trashed the render files & preferences. Reopened the project and re-rendered.
- Exported an XML and looked for clues of inconsistencies.
- Duplicated the sequence and changed the compressor in Sequence Settings from Apple ProRes to Jpeg 2000 and another to Animation. This caused FCP to slow way down and in one instance crashed.
- Media Managed the sequence and reopened it in the new media managed project.
- Re-compressed the sequence through Media Manager, which resulted in a multitude of errors.
What I did discover after all this futzing, is that the audio slip was happening in the render, rather than the export, but how I finally found a solution was by way of Larry Jordan. I submitted my issue on his site for the bargain price of $45.00 and wrote of my woes. And seriously, it was a bargain. I only wish I had done it sooner. I would have saved a lot of time, however, I suppose troubleshooting is a great learning experience, plus it builds character if you don't implode. Anyway, Larry replied in a timely manner and after one or two exchanges, asked me about my sequence settings, which were HDV.
I had tried to find the closest sequence settings to what my video was and I thought HDV was the best match. In all my frantic emails to other editor compadres, I never mentioned the HDV setting, even though I had managed to name every other detail of the project. Larry suggested that I use something else that was close to the majority of my contents specs but to also convert all my audio files through Compressor to be 48kHz, 16-bit and rebuild at least those first 7 minutes of the project. It worked!
I created a new sequence, not using HDV, but an Apple ProRes 422 1920 X 1080p, 24fps. I then used compressor to convert all my audio elements in that first 7 minutes to 48kHz, 16-bit, AIFF stereo audio, then brought those audio files back into my new (non-HDV) sequence. Once I had my sequence rebuilt I rendered. Everything miraculously stayed in place, then I dared to export a Quicktime. Success again. After which I sent my timeline through Compressor to create Mpeg-2 DVD files. Beautiful.
Hope that is helpful to anyone who's experiencing similar problems. I read a lot of threads and it seems that audio slipping can happen in a multitude of circumstances, but this was mine. Best of luck.