Modifying Video Data using FFMPEG

FFMPEG has become very popular for so long time as a tool that can help us manipulate, convert, or configure video and audio data. We can resize our video, convert a file into a different container, change the bitrate, embed subtitles, or even stream real-time video. These are a few examples of its utilization.

Converting file into a different container

For example, we want to convert an MKV file into MP4 without changing its codec.

ffmpeg -i input.mkv -codec copy output.mp4

Or, we want to convert an MP4 file into Webm with some customizations.

ffmpeg -i input.mp4 -c:v libvpx-vp9 -crf 28 -b:v 0 -b:a 128k -c:a libopus output.webm

Change video size

We can resize a video width and height too.

ffmpeg -i input.mp4 -vf scale=1280:720 output.mp4

We can set the width or height to "-1" to keep the origin ratio. Note that some codecs require a size that can be divided by 2 to be successful.

ffmpeg -i input.mp4 -vf scale=1280:-1 output.mp4

Insert subtitles

We can attach a subtitle file to a video container.

ffmpeg -i input.mp4 -i input.srt -c copy -c:s mov_text output.mp4

Extracting subtitles from multi-track video

If a video file is attached with subtitles, we can generate the ".srt" file from it too.

ffmpeg -i input.mkv -map 0:s:0 subs.srt

Embed subtitles

We can also append the subtitle texts into video frames directly.

ffmpeg -i input.mp4 -vf subtitles=input.srt output.mp4

Download Live Stream Video

We can download live steam video from its manifest file and convert it to MP4.

ffmpeg -i http://source.m3u8 -c copy -bsf:a aac_adtstoasc output.mp4

Delay Video/Audio Track

If video or audio tracks are out of sync, we can add some offset to the specific track. For example, we want to cut a video and adjust the audio track.

ffmpeg -i input.mp4 -itsoffset -3.2 -i input.mp4 -map 0:v -map 1:a -c:v copy -c:a copy -ss 12:00 -to 22:30 output.mp4

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