How to extract time-accurate video segments with ffmpeg?

When using FFmpeg to extract video clips, the key is to specify the exact start time and duration. Here is a specific example and step-by-step guide detailing how to use FFmpeg to accomplish this task.

1. Determine the time points for the video clip

First, identify the exact start time (e.g., 00:01:30, starting from 1 minute and 30 seconds into the video) and duration (e.g., 30 seconds) for the clip you want to extract.

2. Use the FFmpeg command-line tool

After determining the time points, you can use the following FFmpeg command to extract the video clip:

bash
ffmpeg -ss 00:01:30 -i input_video.mp4 -t 00:00:30 -c copy output_clip.mp4

Here are the parameter explanations:

• -ss 00:01:30 specifies the start time (starting from 1 minute and 30 seconds into the video).
• -i input_video.mp4 specifies the input file name.
• -t 00:00:30 specifies the duration (30 seconds from the start point).
• -c copy indicates the "copy" mode, meaning no re-encoding is performed, which allows for faster extraction while preserving the original quality.
• output_clip.mp4 is the output file name.

3. Verify the output

After executing the command, FFmpeg will extract the specified time segment and save it as output_clip.mp4. You can use any media player to check the output file and confirm that the video clip has been correctly extracted.

4. Important considerations

• For precise clipping on non-keyframes, you may need to omit -c copy to perform re-encoding, which allows starting from any specified frame, but this may affect processing speed and file size.
• Ensure that the time format of the input file matches the actual video length to avoid errors.

By following these steps, you can accurately extract specific segments from video using the FFmpeg tool. This is very useful in various scenarios such as video editing and content production.

ffmpeg is a powerful command-line tool for processing video and audio files. Below, I will describe how to use ffmpeg to extract video clips and provide a specific command-line example.

To extract time-accurate video clips using ffmpeg, you need to know the following:

1. The path and name of the video file.
2. The start time of the video clip you want to extract.
3. The duration or end time of the clip.

In ffmpeg, you can use the -ss parameter to set the start time, the -t parameter to set the duration, or the -to parameter to set the end time. Time format is typically HH:MM:SS or just SS.

Below is a command-line example where I extract a clip from a video file named input.mp4, starting at the 10th minute and lasting 30 seconds:

bash
ffmpeg -i input.mp4 -ss 00:10:00 -t 00:00:30 -c copy output_clip.mp4

In the above command:

• -i input.mp4 specifies the input file.
• -ss 00:10:00 sets the start time to the 10th minute of the video.
• -t 00:00:30 sets the duration to 30 seconds.
• -c copy indicates the "copy" mode, which copies the video and audio streams without re-encoding (faster but potentially less precise).
• output_clip.mp4 is the name of the output file.

If you require higher time accuracy, it is recommended to place the -ss parameter after -i, so ffmpeg first quickly jumps to the approximate position and then precisely extracts based on encoded frames. However, this method may be slower as it re-encodes the video. For example:

bash
ffmpeg -ss 00:10:00 -i input.mp4 -t 00:00:30 -c:v libx264 -c:a aac output_clip.mp4

In this example:

• -c:v libx264 specifies the video encoder as libx264, which is the H.264 encoder.
• -c:a aac specifies the audio encoder as aac.

This is the basic method for extracting time-accurate video clips using ffmpeg. Depending on your needs, you can add other parameters to adjust the video resolution, bitrate, etc.