Is my cutting method lossless?
Here’s what I did:
Step 1: Find keyframes
D:\>ffprobe -loglevel error -select_streams v:0 -show_entries packet=pts_time,flags -of csv=print_section=0 input.webm | findstr "K"
0.000000,K__
1.502000,K__
4.638000,K__
9.510000,K__
[opus @ 0000027726e9c000] Error parsing Opus packet header.
Step 2: Cut at keyframes
ffmpeg -ss 1.502000 -i input.webm -c copy -to 9.510000 output.webm
Start time: 1.502000
End time: 9.510000
Step 3: Check the output video
D:\>ffprobe -loglevel error -select_streams v:0 -show_entries packet=pts_time,flags -of csv=print_section=0 output.webm | findstr "K"
0.000000,K__
3.136000,K__
8.008000,K__
[opus @ 000002292742c000] Error parsing Opus packet header.
I think the output video is lossless because:
1.502000 - 1.502000 = 0.000000
4.638000 - 1.502000 = 3.136000
9.510000 - 1.502000 = 8.008000
The keyframes are simply shifted, so I believe the cut is lossless.
Is my cutting method lossless?