There are a million ways to transcode video, so in this example, we will use the most common video encoder H.264/AVC. Unfortunately this will introduce generation loss, depending on the settings. Cutting video (exactly) with transcodingīy re-encoding the video, FFmpeg is able to cut the video at exact points in time. To understand why this happens you can read more about keyframes. Instead, FFmpeg tries to find the closest keyframe and cut it there. However, FFmpeg cannot cut at exact points in time unless it re-encodes the video. This is a great way to maintain the original quality, thus avoiding generation loss. If you don’t mention copy, re-encoding is the norm.FFmpeg is able to cut, trim and extract videos without transcoding the media. If you want to cut specifically at a non-keyframe and have it play at the desired point on a player that doesn’t support edit lists, or if you want to make sure the cut section isn’t in the output file (for example, if it includes sensitive information), you can do so by re-encoding so that a keyframe is present at the desired start time. Some players can disregard the edit list and play the entire file from beginning to end, regardless of the edit list. If this does not work for you, it is you are likely using an older version of FFmpeg or that your player does not support edit lists. If you’re using the latest version of FFmpeg from git master, it’ll use an edit list when you run it with the command you give. In other words, if the closest keyframe before 3s is at 0s, the video will be copied starting at 0s, and FFmpeg will use an edit list to tell the player to begin playing 3 seconds in. Using an edit list, it is possible to cut at a non-keyframe with the mp4 container without re-encoding.

Non-keyframes need all of the data beginning with the previous keyframe because they encode variations from other frames. You probably don’t have a keyframe at the specified second mark if you can’t cut a video at a particular moment. In GNU/Linux tagged cut / ffmpeg / time by Tux

Ffmpeg cut video from time to time