media_trim

Trims an audio or video file using ffmpeg.

• Works with all formats supported by ffmpeg, including mp3, mp4, mkv, and many more.
• Seeks to the nearest frame positions by re-encoding the media.
• Reduces file size produced by OBS Studio by over 80 percent.
• Can be used as a Ruby gem.
• Installs the trim command.

Installation

You need a working Ruby environment to install this program. I describe how to set that up here.

Standalone

The trim command is provided by the media_trim Ruby gem. Install it like this:

$ gem install media_trim

As a Dependency of a Ruby Program

Add this line to your application’s Gemfile:

gem 'media_trim'

Then execute:

$ bundle

As a Dependency of a Ruby Gem

Add the following to your application’s .gemspec:

spec.add_dependency 'media_trim'

Then execute:

$ bundle

Usage

Command-line Usage

trim [OPTIONS] dir/file.ext start [[to|for] end]

• The start and end timecodes have the format [HH:[MM:]]SS[.XXX]. Note that decimal seconds may be specified, but frames may not; this is consistent with how ffmpeg parses timecodes.
• end defaults to the end of the audio/video file

When run as a command, output files are named by adding a trim. prefix to the media file name, e.g. dir/trim.file.ext. By default, the trim command does not overwrite pre-existing output files. When trimming is complete, the trim command displays the trimmed file, unless the -q option is specified.

OPTIONS are:

• -d Enable debug output.
• -h Display help information.
• -f Overwrite output file if present.
• -v Verbose output.
• -V Do not view the trimmed file when complete.

Examples

Crop dir/file.mp4 from 15.0 seconds to the end of the video, save to demo/trim.demo.mp4:

$ trim demo/demo.mp4 15

Crop dir/file.mkv from 3 minutes, 25 seconds to 9 minutes, 35 seconds, save to demo/trim.demo.mp4:

$ trim demo/demo.mp4 3:25 9:35

Same as the previous example, using optional to syntax:

$ trim demo/demo.mp4 3:25 to 9:35

Save as the previous example, but specify the duration instead of the end time by using the for keyword:

$ trim demo/demo.mp4 3:25 for 6:10

Figuring Out Start and Stop Times

Need a way to figure out the start and stop times to trim a video? DJV is an excellent video viewer.

• Allows frame-by-frame stepping
• Displays the current time reliabily
• F/OSS
• Mac, Windows, Linux
• High quality

Development

After checking out this git repository, install dependencies by typing:

$ bin/setup

You should do the above before running Visual Studio Code.

Run the Tests

$ bundle exec rake test

Interactive Session

The following will allow you to experiment:

$ bin/console

Local Installation

To install this gem onto your local machine, type:

$ bundle exec rake install

To Release A New Version

To create a git tag for the new version, push git commits and tags, and push the new version of the gem to https://rubygems.org, type:

$ bundle exec rake release

Contributing

Bug reports and pull requests are welcome at https://github.com/mslinn/trim.

License

The gem is available as open source under the terms of the MIT License.