Syncing by Audio

Question

Hi there,
When syncing by audio, what's happening when I offset the audio frames from the video frames?
I was looking around for official documentation on this, but couldn't find any.
I'm thrilled that the new Premiere Pro CC (7.0.0) can sync by audio. I can cut out PluralEyes from my workflow entirely. I'd just like to know what's happening when I modify the numerical value for "Offset audio by _ video frames" when I generate a new multi-camera source sequence.
Operators of older DSLRs, like the T2i, 5D Mk II, and 7D, know that these cameras' own internal audio tracks are out of sync with their video, usually having their video tracks lag behind their audio tracks by a single frame or two, depending on the camera.
Does this feature actually offset video and audio within a clip that has its audio and video tracks linked? Does it look for isolated audio tracks that have no video associated with them and simply offset those from the video clips that do have audio? I noticed that isolated audio tracks are automatically moved to A1 and are soloed, so they seem to have special priority.
Also, which direction does the offset move the tracks? I'm assuming I can put in positive or negative values and get different results.
Please help!

Answer 1

OK, I ran some experiments. I started with a large absolute value of 24 so that I would really notice what was going on, hoping to see stuff about a full second out-of-sync.
Test 1:
Footage used:
Frame-accurate FS100 AVCHD MTS footage
Frame-inaccurate 5D Mark II H.264 MOV footage
No separate audio tracks unassociated with video
Operation:Value set to 24 [positive]
Results:
FS100 audio was synced to 5D audio
FS100 video remained frame accurate with its own audio
5D video remained out of sync by a frame with its own audio
Test 2:
Footage used:
Frame-accurate FS100 AVCHD MTS footage
Frame-inaccurate 5D Mark II H.264 MOV footage
No separate audio tracks unassociated with video
Operation:Value set to -24
Results:
FS100 audio was synced to 5D audio
FS100 video remained frame accurate with its own audio
5D video remained out of sync by a frame with its own audio
At this point, I determined that no offsets were being manifested within the original clips themselves. Now it was time to add in an audio track unassociated with any video.
Test 3:
Footage used:
Frame inaccurate 5D Mark II H.264 MOV footage
One separate audio track unassociated with any video
Operation:Value set to 24 [positive]
Results:
Lone audio track synced to 5D audio
5D clip remained out of sync with its own video by a frame
At this point, I thought I had done something wrong, or missed something, because even Test 3's lone audio track manifested no offset with the other clips. Just to make sure that I wasn't missing anything, I increased the offset to 48 frames in Test 4, hoping for the tracks to be a full two seconds out-of-sync.
Test 4:
Footage used:
Frame inaccurate 5D Mark II H.264 MOV footage
One separate audio track unassociated with video
Operation:Value set to 48 [positive]
Results:
Lone audio track synced to 5D audio
5D clip remained out of sync with its own video by a frame
Test 5:
Footage used:
Frame inaccurate 5D Mark II H.264 MOV footage
One separate audio track unassociated with video
Operation:Value set to -48
Results:
Lone audio track synced to 5D audio
5D clip remained out of sync with its own video by a frame
So, as far as I can tell, the feature is actually completely non-functional. This is pretty annoying, Adobe! I still use these older DSLRs, and would love to actually be able to rely on this feature!
I'll submit a bug report.