I have a number of .mp4 files that have material transferred from VHS tapes and would like to extract sections from each file that I want to keep.
I picked up a copy of Losslesscut as this looked like it would do the job nicely. However, just been through the first of the files and Exported the bits I want and was disappointed to see that the start/end of each extracted segment is not exactly where I wanted.
Noticed this was using the "Keyframe Cut" method and changed to "Normal Cut" - this is better, but, leaves a bit of blank before picture kicks in!
So, first question is......should LosslessCut be able to do what I want and extract accurate sections?
If it can't then are there any other tools I could look at that will?
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You can't get frame accuracy and lossless cutting with interframe codecs (pretty much all high compression codecs like MPEG 2, AVC, HEVC...). This is because most frames only encode the changes between earlier/later frames and the current frame. Without those earlier and later frames those frames can't be reconstructed. A Group Of Pictures (GOP) starts with a key frame (encoded much like a JPEG image, all the data the reconstruct the keyframe is included in that frames data) but other frames of the GOP (which can be hundreds of frames long) only contain the changes. For example, in a talking head shot the background may not change from frame to frame, only the speaker's lips move. The key frame will include everything needed to reconstruct that frame (and will be relatively large). But the next frame will only contain data for the moving lips. In essence it says "copy the previous frame, then add these changes for the moving lips." Not repeating all the information for the background is an enormous savings.
In short, for frame accurate cutting you will need to reencode the cut GOPs. Most editors will reencode the entire video when set for accurate cuts. There are some "smart" editors that will only reencode the cut GOPs. VideoRedo for example.