I have a half hour program that was edited in FCPX as 30p...and I am doing a Send to Compressor off the timeline and using a custom Blu Ray preset for h264 transcoding to an image disc In the retiming pane of the video encoder, I am checking the box so that "source frames will play at 29.97"...and this increased the program length by 0.01%...coming out to 1 second and 19 frames longer than it would be if it were a native 30p transcode.
The new video duration was indicated as 27:26:21...and this showed up in the separate audio encoding pane as well...and your choice is to pick either the "audio duration at 100% of source"...or...I could check the "new duration running time of 27:26:21." My reason for selecting the latter was it seemed like the audio encoding would stretch and correct pitch for the new slightly longer length of the video.
However, when playing back the burned DVD, the video quality was smooth and excellent but audio was actually too short in duration gradually throwing the project more and more out of synch as playback continued.
For the Bly Ray transcode audio pane, should I have chosen the first setting...set duration for 100% of source. And perhaps it will auto adjust to the new slightly longer length of the video?
Or perhaps what I need to do is give Compressor a 30p Pro Res Master of the program to do the 29.97 Blu Ray transcode....where the audio is married to the video...and perhaps then the audio length will be properly adjusted and everything will be in sync.
Alright, so after more trial and experimentation, I am replaying to my own post as I have found the best way to burn a 29.97 fps Blu-Ray from a 30p FCPX timeline.
First, the wrong way...
If you apply the Compressor custom Blu-Ray setting, it will auto apply the 29.97 frame rate....and the default setting is to "play at 100% of source material." And leave the audio default setting alone. This will produce a Blu-Ray DVD, but it will have some visual stutter here and there...frames apparently being dropped by the transcode.
Second, the right way...
After you apply the custom Blu-Ray setting, it will show 29.97 but then further modify that by checking the box that says "so sources frames play at 29.97"...this will slow down the picture playback by 100.10%. And it will force every frame to be transcoded with no dropped frames.
And then in the audio pane, change the duration time so it shows as 100.10% of source....this duration will extend the audio and match it time wise to the video. Even though the audio is slowed down very slightly, Compressor will automatically change the pitch.
And together this combination of video and audio settings in the Compressor's Blu-Ray present will head a great looking picture, very smooth, and audio will be in sync.
I realize this info is probably only aimed at a small section of users who may be transcoding 30p timelines into a 29.97 Blu-Ray, but it sure looks like the way to go. I only wished I had discovered this sooner!