Quicktime Pro edits like "cut" lossless? No re-encoding, re-compression...?

Question

Hi,
Does importing, for example, a Motion JPEG file into Quicktime Pro to remove a segment in the middle, or cut off material from the ends, leave all original settings (compression, quality, etc.) intact?
Or might it change settings to match those in Quicktime Preferences or re-encode in some way?
From playing with the app:
It looked to me that "Save" only changes how the file is played, skipping the "cut" segments, as the file size is the same.
"Save-as a self contained movie" appears to actually remove the cut material as file size decreases. No mention is made of settings.
Export seems to re-encode etc., as many options are presented - and the original format in the example, Motion-JPEG, is not even one of them.
Thanks.

Answer 1

Does importing, for example, a Motion JPEG file into Quicktime Pro to remove a segment in the middle, or cut off material from the ends, leave all original settings (compression, quality, etc.) intact?
Yes. Even the file container remains unchanged.
Or might it change settings to match those in Quicktime Preferences or re-encode in some way?
No, it doesn't. The only things than may change might be the Inspector window statistics. For instance, if you remove a clip segment containing dark, low-complexity scenecs, the average video data rate may be higher because you deleted a segment containing extremely low video data rates.
It looked to me that "Save" only changes how the file is played, skipping the "cut" segments, as the file size is the same.
This is essentially true. Basically, the blocks of data are just "re-linked" to "skip" the unwanted segment. The file container size is not changed and the "skipped" data remains essentially present but no longer accessible.
"Save-as a self contained movie" appears to actually remove the cut material as file size decreases. No mention is made of settings.
In this case, an entirely new MOV (generic QT) file container is created and the "retined" data is "copied" from the original file to the new one. The file is smaller because the "skipped" data is not copied. Original compression formats (i.e., a copy of the very same data) is contained in the new file. A "Reference" file does something similar. However, it does not actually copy the actual data from one file to the new file. Instead, it mearly copies pointers to the original data allowing you to create one or more playback variations of the original file. This can be a handy expedient when creating "what if" versions of the same master file since the references files are much smaller than the original file. The only thing you have to remember is that the original file cannot be deleted since the "reference" file only contains instructions as to how the original file is to be played back in some "modified" manner.
Export seems to re-encode etc., as many options are presented - and the original format in the example, Motion-JPEG, is not even one of them.
Correct. In this case, the original data is re-compressed as a new file and in a new container. Remember, however, that re-compressing data does not enhance or improve quality since it can't add or create details lost during previous compression. It can, however, reduce further loss of details/quality by selectively using a low compression format which retains all/most of the detail/quality in the source file. This is often done where a user wants to edit highly compressed data which cannot be edited natively in the original compression format otherwise.