Problems with hard cutting videos when using different frame rates and speed control

Question

I'm trying to create a video in blenders video editor that involves a talking head in the corner that is "alpha overed" a power point slide using a transform. The two videos have different frame rates which is the first problem. I have addressed this problem by using speed control in order to "match" the two videos. After I do this the videos are synced correctly.

However, due to errors on the narrators part I have to clip certain parts of both videos at the same times to delete the errors. When I perform a hard cut in the area I want to remove footage from, the footage seems to shift. I don't see any clear pattern, but it is as though when I perform the hard cut the video section I wanted to remove changes and a different part of the video gets cut. This is extremely frustrating. Any advise would be incredibly appreciated. Let me know if there is any more information I can give to clarify the problem.

Answer 1

I strongly suspect this is a bit of a duplicate question, even though it isn't terribly clear to a cursory examination. That is, I have a hunch that your image and / or video is compressed using a relatively highly compressed codec. When this happens, especially with long Group Of Pictures codecs (long GOP), you can expect that your hard cuts will not be able to be maintained because you will likely have cut in the middle of one of these GOP runs. When this happens, your video is unable to properly sync because the precise frame cut position has happened in a place that is unrecoverable, and as a result the codec decoder must resume from the previous "whole" frame.

While this might not be apparent immediately, similar sorts of issues crop up with heavily compressed audio and the result is very similar.

So how to resolve this? Convert your entire stream or streams to a native image format or AVI JPG series, and audio to WAV format.

Why does this solve the issue? Because then, wherever you place a cut, the image and audio have an immediate ability to be resumed at wherever the cut point ends up, without requiring a "rewinding", which is causing the issue.

While I am not 100% certain, I would wager that there is a greater than 50% chance this is your issue. If it turns out to be the case, there are other folks that are vastly more capable at finding the duplicates and citing them here.

Answer 2

Just use nested Scene Strips. Since 2.77 you can Add a Scene into another Scenes VSE and cut out parts of your perfectly timed matching strips in this original Scene.