Hi there!
I'm having a rough go with a project that syncs audio/video fine within Premiere, but on export, the sync drifts in and out significantly.
Specifically, after doing some digging, I noticed that in the exported version, some video clips are shifted by several frames compared to where they are in the Premiere project, but are the same length as the clips in the project. For example, in one instance, the in and out points of a clip were offset by six frames in the export compared to how I'd edited it in the project, but the clip duration was the same amount of frames. Other video clips are issue-free. This has not impacted the audio at all; in every export, it stays in the same time as in the project.
Here's a list of all the things I've tried to fix this, all with the same result:
- Export settings:
- H.264 with Match Source and other configurations with the same settings (or downscaled) as the source media and timeline
- with both Variable and Constant bit rates
- QuickTime using CineForm and ProRes codecs with the same settings (or downscaled) as the source media and timeline
- Exporting through Premiere Pro CC and Media Encoder CC
- Playing back exported media on QuickTime Player and VLC Media Player and within Premiere
- Unlinking all audio and manually re-syncing, then exporting again
- Copying and pasting the media into a new sequence, then exporting again
- Replacing clips with sync issues with other takes
- Uninstalling Premiere, then reinstalling an older version (12.1.1)
- After this didn't work, reinstalling the current version (12.1.2)
- Clearing media caches in Premiere and Media Encoder
- Deleting render files
- Rendering and replacing (caused clips to become out of sync in timeline; more on that below)
- Exporting video and audio separately, then recombining them in a new sequence
- Transcoding the variable frame rate video files to a constant frame rate using Handbrake, re-syncing audio, then re-editing the sequence
Here's some info about the project media, my system, and workflow:
- Project:
- Video: 3840x2160. Originally recorded as 24fps variable QuickTime, then modified to 23.976 in Premiere. Alternately transcoded to 24fps constant H.264 in Handbrake, then modified to 23.976 in Premiere.
- The video was shot on an iPhone using FiLMiC Pro — yes, I know phones are notorious for variable frame rates and sync drift (more on that below).
- Audio: 48kHz wav.
- System:
- iMac 27" 5K running MacOS High Sierra 10.13.6
- 3.4GHz i5, 40GB RAM
- Premiere Pro CC 12.1.2 and Media Encoder CC 12.1.2
- Workflow:
- I'm using proxies because of the 4K footage. My proxy settings are 1280x720 23.976fps QuickTime.
When using proxies within Premiere, my project is perfectly in sync with no drift either in my main timeline or in my selects timelines. My system won't reliably play back the 4K footage when proxies are toggled off, but I found that by copying troubled clips, then rendering, replacing, and toggling the rendered copy on and off, the video would sometimes show different frames at the same timecode, shifting the video in the same way I mentioned above. I originally thought this was due to the variable frame rate of the original media, which is why I transcoded everything to a constant frame rate. However, even with those transcoded files as the source media, I am still having the same issue.
And it's worth restating that not all clips are affected equally by this. One clip from a single take might be off by just a few frames, but the next one from that same take will be off by plenty more, and the one after that will have no problem at all. I haven't noticed any pattern of which clips are having issues or why.
I would try using the original footage completely unmodified with Premiere's new variable frame rate options, but because I need to use proxies, that feature is not supported.
To the possible criticism of using a phone camera with Premiere: while there are sometimes sync drift issues with this, they've always shown up within Premiere in my experience, and I've thus been able to correct them in the timeline and export without issue. In this project, the sequence has no sync issues within Premiere (while using proxies), but only has a problem on export, which is a new issue for me.
On a lark, and only because it was shot on an iPhone, I tried putting some original footage into iMovie, syncing the audio, and exporting it. This worked once, but on other tries, the sync drifted considerably, so it doesn't seem like a viable workaround.
At this point, all I can think to do is manually add and subtract frames to and from an exported file and then re-export, but that's obviously not something I should have to do.
Does anyone have any clue what's happening or what I'm missing here? I've got a deadline looming and don't have many more hours to troubleshoot this — or many more hairs to pull out.
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