If I open a movie in Quicktime Player on my Mac, trim it, then save that new file, is the quality of the new movie the same as the original? In other words, is trimming in QuicktimePlayer lossless?
If it matters… the movie was shot on an iPhone 12 at 60fps at the highest setting. I don't want dropped frames or lesser codec quality.
iMac Line (2012 and Later)
Previously I have used MPEG Streamclip for lossless H.264 trims in Mojave and earlier systems that support 32-bit apps.
I have tested this and it seems that at least H.264 and H.265 Big Sur (and AFAIR also Mojave and Catalina) QuickTime Player trims are also lossless.
The input and output quality is the same (I have compared exported frames in Photoshop) and it saves so fast that it does not have time to re-encode.
Unlike apps like MPEG Streamclip or Avidemux, QuickTime Player does not show GOPs and I frames and lets the user trim at arbitrary points inside the GOP (i.e. also at P and B frames) but it seems it does not even then re-encode the starts and ends but just does not display the trimmed frames (some other apps might then open at blank frame or the down arrow does not go to last frame).
Previously I have used MPEG Streamclip for lossless H.264 trims in Mojave and earlier systems that support 32-bit apps.
I have tested this and it seems that at least H.264 and H.265 Big Sur (and AFAIR also Mojave and Catalina) QuickTime Player trims are also lossless.
The input and output quality is the same (I have compared exported frames in Photoshop) and it saves so fast that it does not have time to re-encode.
Unlike apps like MPEG Streamclip or Avidemux, QuickTime Player does not show GOPs and I frames and lets the user trim at arbitrary points inside the GOP (i.e. also at P and B frames) but it seems it does not even then re-encode the starts and ends but just does not display the trimmed frames (some other apps might then open at blank frame or the down arrow does not go to last frame).
you could always make a duplicate of the original file first, and experiment with the duplicate to see where it leaves you without affecting the original. but i think it just removes the trimmed portion without affecting the rest of the recording.
i've never used an iPhone video with QT. but whenever i have trimmed a screen recording with QT, i've not noticed any loss of definition or audio quality. so i imagine you will get the same result with your videos recorded on the iPhone.
I think it boils down to whether or not QuicktimePlayer *recompresses* a trimmed movie, or if it simply lops off the portions that are removed. Unless I'm over-simplifying.
Is trimming a movie in QuicktimePlayer lossless?
