Editing

Overview ​

Video and audio converter. To get information of a file, use ffprobe input.mp4.

More references:

• Audio Channel Manipulation
• Audio Volume
• Filters
• Formats

Usage ​

ffmpeg GLOBAL_OPTIONS INPUT_OPTIONS -i input_url OUTPUT_OPTIONS output_url

-filter_complex cannot be used with the simple filter options -af -vf. The syntax is [NUM_INPUT:CHANNEL]FILTERS[LABEL].

List available encoders with:

Video manipulation ​

Lossless copy ​

Copy part of the video with -codec copy -avoid_negative_ts make_zero. It will adapt the -ss to the previous I-Frame.

ffmpeg -ss 02:19 -to 08:18 -i full.mp4 -codec copy -avoid_negative_ts make_zero cropped.mp4

Video Trim ​

Remove segments from a video/audio.

Bellow an example of removing the segment 00:39:28 - 00:53:10 from a video and audio.

Single input ​

Read the whole video/audio once and trim using the trim filter. start end parameters are read in seconds.

The segment to be removed will still be decoded and later discarded, so may be a little slow.

ffmpeg \
  -ss 00:00:43.000 -to 01:42:56.000 -i video.mp4 \
  -ss 00:00:43.700 -to 01:42:56.700 -i audio.m4a \
  -filter_complex \
   '[0:v]trim=start=2368:end=3190,setpts=PTS-STARTPTS[0v];
    [1:a]atrim=start=2368:end=3190,asetpts=PTS-STARTPTS[0a];
    [0v][0a]concat=n=1:v=1:a=1[outv][outa]' -map '[outv]' -map '[outa]' \
  result.mp4

Split input ​

Read the same video/audio multiple times with different start/end times, and concat them.

This method may have better performance because there is no decoding of the frames that will be discarded.

ffmpeg \
  -ss 00:00:43.000 -to 00:39:28.000 -i video.mp4 \
  -ss 00:00:43.700 -to 00:39:28.700 -i audio.m4a \
  -ss 00:53:10.000 -to 01:42:56.000 -i video.mp4 \
  -ss 00:53:10.700 -to 01:42:56.700 -i audio.m4a \
  -filter_complex
   '[0:v][1:a][2:v][3:a]concat=n=2:v=1:a=1[outv][outa]' -map '[outv]' -map '[outa]' \
  result.mp4

Video Scale ​

Resize the video to the specified width:height. If -1 is used, keep aspect ratio.

ffmpeg -i video.mp4 -vf 'scale=960:-1:flags=lanczos' rescaled.mp4

Video Crop ​

Crop a portion of a video. Syntax: crop=W:H:X:Y

• W: Width of the output
• H: Height of the output
• X: Horizontal position from where to begin cropping
• Y: Vertical position from where to begin cropping

ffmpeg -i video.mp4 -vf 'crop=600:400:660:340' cropped.mp4

Video Fade ​

Use the fade video filter to fade the video in or out. Parameters:

• st is the start time, in seconds
• d is the duration, in seconds

Considering an 90 seconds long video file, fade in the first 1 second and fade out the last 1 second.

ffmpeg -i video.mp4 -vf 'fade=in:0:d=1,fade=out:st=89:d=1' out.mp4

Shortest ​

Set -t or -to only for one channel, and all channels will be cut at that timing too.

ffmpeg \
  -ss 05:00 -t 32 -i video.mkv \
  -ss 05:00 -i rec.flac \
  -ss 05:00 -i mix.flac -shortest \
  # ...

It does not always work. You may need to manually set the desired time with -t or -to for all channels.

Audio manipulation ​

Volume ​

Use the volume audio filter to increase or reduce the volume of the audio. Allowed values are:

• A float value: 1.5 (50% increase)
• A dB value: 15dB

ffmpeg -i low_volume.m4a -af 'volume=15dB' adjusted.m4a

Audio Fade ​

Use the afade audio filter to fade the audio in or out. Parameters:

• st is the start time, in seconds
• d is the duration, in seconds

Considering an 90 seconds long audio file, fade in the first 1 second and fade out the last 1 second.

ffmpeg -i audio.m4a -af 'afade=in:0:d=1,afade=out:st=89:d=1' out.m4a

Mono to stereo ​

Create single stereo file ​

You can use either -ac 2 or a -filter_complex.

ffmpeg -i mono.mp3 -ac 2 stereo.m4a
ffmpeg -i mono.mp3 -filter_complex '[0:a][0:a]amerge=inputs=2[outa]' -map '[outa]' stereo.m4a

Merge mono with stereo ​

ffmpeg -i mic.flac -i speakers.flac -filter_complex 'amerge=inputs=2' -ac 2 mix.flac

If you messed up with recording the mono audio (forgot to use -ac 1), you can try the following:

ffmpeg -i mic.flac -i speakers.flac \
  -filter_complex \
   '[0:a][0:a]amerge=inputs=2[0a];
    [0a][1:a]amerge=inputs=2[outa]' -map '[outa]' -ac 2 \
  mix.flac