I like using the Trim feature in Finder for shortening and cataloging clips prior to importing into FCPX. Does anyone know if video files are compressed during this process?
MacBook Pro 16″, macOS 14.5
As far as I know, the answer is no. You can tell this by examining the bit rates of the original and trimmed files which should be identical.
As far as I know, the answer is no. You can tell this by examining the bit rates of the original and trimmed files which should be identical.
With which codecs do you see a difference? I've checked it with ProResRaw, ProResHQ, H.265 and H.264. I'm looking at the data rate parameter in the Movie Inspector in Quicktime. I tried trimming in the Finder and in Quicktime which can give very slightly different results. There might be very minor differences, maybe due to something in the metadata and the trimmed versions might be slightly bigger than the originals. So I don't think there is any compression. ProRes Raw files show no change at all.
Clint Gryke wrote:
As far as I know, the answer is no. You can tell this by examining the bit rates of the original and trimmed files which should be identical.
Thanks Clint. This is reassuring to know. I should have done that myself.
It tried it in AVCHD for a short clip and checked the bit rate in MediaInfo. There wasn't much difference on a short file but they weren't the same. The trimmed version had the lower bit rate.
It may depend on the codec of the original. If you trim the clip and see Untitled at the top of the window, a new file is being created. The bit rate seems to be different.
Yes I shouldn't have said identical in my first post - very similar would have been better. However, I think it is probably safe to say there is no compression, at least for the file types I checked.
On a related note regarding video compression. I recently wanted to do a safety check and make sure my colour grade of my Rec. 709 project comprised of HLG BT 2020 clips, looked okay on Rec 709 displays. When I used the Apple TV Home Movies to view the project on my early LG Smart TV, the compression was terrible. Initially, I thought it was my color grade that was the problem, but it appears that it was Home Movies that was creating the gamma/contrast issues and compressing the video.
If you want to test out a SDR color grade on your TV, I found using Apple screen mirroring via Apple TV to be the best way to do a Rec 709 safety check. There were not contrast or gamma issues when I viewed the video this way.
Thanks Tom. So do you think the compression is so negligible it won't affect video quality?
I would trust Clint’s judgement on this, but I couldn’t see any difference in the files. It was a fairly easy image to recompress however.
When you use the video Trim feature in Finder is the HDR footage compressed when you safe the file?
