ffmpeg video trimming without freezed starting frames

Question

I am using the following commands for cutting videos using ffmpeg. However, they are presenting weird results.

When I am using the following command, the output video has its frames freezed for starting 1 or 2 seconds and plays smooth later.

ffmpeg -i input.mp4 -vcodec copy -acodec copy -ss 30 -t 45 out.mp4

Whereas, this commands solves the problem of freezed frames but seeking is not accurate as I am using -ss parameter before input.

ffmpeg -ss 30 -i input.mp4 -vcodec copy -acodec copy -t 45 out.mp4

I am looking for help that will let me come up with a solution that will accurately clip the video without freezing frames.