I have two videos I want to edit together, both are single long takes of the same event, taken from different angles with different cameras. One is from an older Sony camcorder, 29 minutes long, 720x480, 29.97 fps; the other from an iPhone 6, 27 minutes long, 1920x1080, 30 fps. Each has problems at various times, so I'd like to combine them with intercuts. I understand that my first step is to convert the framerates to match. What's the best way to do this? I've seen recommendations to use FFmpeg. With the frame rates so similar, is this overkill? Thanks.
You will need to conform the footage to a single base rate. Although being very close, the values will be significantly off enough to cause sound slippage.
Regarding the Apple device, if from North America, I have extreme doubts that the footage is a base 30 rate. Typically most North American devices will list 24P or 30P and yet still be NTSC 24000/1001 and 30000/1001 respectively.
FFMPEG is probably a great entry point to conform any footage that requires such. Bear in mind that this may well have adverse effects on your footage as the frames in question may be dropped or doubled up depending on which target frame rate you are conforming to.
The program that I use to convert my video footage to the same frame rate is Handbrake (https://handbrake.fr/). It's fairly easy to use.
Generally, in Handbrake, I change Anamorphic to none, Constant Quality down to Zero, and then I set to Constant Framerate.
When editing video in Blender, you almost always want to use the same exact framerate. I convert everything to the output framerate through handbrake first.
You could open the 'Video Sequence Editor', click 'Add', 'Movie' and open the first movie (from Sony). In the properties panel, change the fps according to that video and render it to images.
Then open a new Blender, open 'Video Sequence Editor', click 'Add', 'Image', and select every rendered image of the previous video. Now change in the properties panel the fps to 30 fps and render it as video. Now you have both videos at 30 fps.
Use AviSynth before using Blender to convert/change to the correct Frame Rate and then mount your AVS file with AFSmount and open the virtual AVI file in Blender.
If you use FFMPEG use it cautiously, it's not a playtool.
I'd recomend doing several steps like retime, recode, transcode both in a unique reading format so the editing tool doesn't crash in the middle of a computation. Setting a common frame rate won't hurt the audio at all depending on the tools, so plan your match before you play.
Once you've got both at the same frame rate, print size then you pull the audio track and get a single audio track from both.
Essentially you'd master it using 'steinberg's wavelab. Do not remove frames from audio. Just silence it using a fade. Once the studio audio is push, then join it from a separate track in your favorite compositing tool. Then cut and fade video at will in a single pass – the output will be transcoded to the final formats. Good luck.