ffmpeg - Finding the right point to cut

Question

I cut videos using the command below, and I sometimes find that the resulting video has imperfections at the beginning (square artifacts in the image). If I advance the start time parameter value (START_AT_SECONDS) by a few seconds (usually 1..3s), the artifacts go away.

Is there a way to avoid the hit-and-miss, e.g. to know in advance that START_AT_SECONDS=53 works but START_AT_SECONDS=52 will give artifacts? Is there an option that means "START_AT_SECONDS=52, or later as needed to make a good cut"?

ffmpeg -ss START_AT_SECONDS -i "some_file_name.mp4" -t DURATION_SECONDS -c copy "new_name.mp4"

Answer 1

There is a mistake in your ffmpeg command.

The -c option either needs a codec (e.g. -c:v libx264) if you want to encode the video or the special value "copy" if it shouldn't be re-encoded (-c copy).

Using -ss together with -c copy might not be accurate since ffmpeg is forced to only split on i-frames. But starting on an i-frame should fix the problem with artifacts.