Taming Multimedia with ffmpeg

Suddenly, your disk is full of photos and videos, and there are new trips ahead. What to do, buy a new one, rent a disk space on the cloud, or can it better compress video files via ffmpeg ?

But why limit yourself to saving disk space? I propose to learn the amazing possibilities of processing photos, audio and video data, command line utilities.

Ffmpeg library and video processing

The open source library ffmpeg is most likely already installed on your operating system. If not, install it with a regular package management program; it won't take long.

Convert one format of audio and video files to another

ffmpeg -i file.<old_extension> [options] file.<new_extension>

Reduce the video recorded on the camera:

 ffmpeg -i MVI_4703.MOV MVI_4703.avi

The same, but with quality control.

 ffmpeg -i MVI_4703.MOV -q:v 4 MVI_4703.avi

The video size has decreased by more than 5 times without noticeable loss of quality. The -qscale:vn option, abbreviated to -q:vn allows you to set the quality level of the generated video stream, where n takes values in the range from 1 to 31. Value 1 corresponds to the best quality, and 31 - to the worst.

 -rw-r--r-- 1 mig users 124M  18 23:29 foto/MVI_4703.avi -rw-r--r-- 1 mig users 686M  27 21:38 foto/MVI_4703.MOV

Specify codec

To select the codec we need, use the -c:a <codec> -c:v <codec> keys.

 ffmpeg -i video.mp4 -c:v vp9 -c:a libvorbis video.mkv

You can see all supported codecs using the ffmpeg -codecs .

Change file container

Now take this ~~user case~~ happening. Your TV's built-in player supports the mkv format, but does not support m4v. In order to change the container, use the following command.

 ffmpeg -i video.m4v -c:av copy video.mkv

If you only need to change the sound, and leave the video as it is, run this command. For some reason, Phillips TVs understand only the AAC / AC3 audio formats.

 ffmpeg -i video.m4v -c:v copy -c:a aac video.mkv

Add audio track

Simply enumerate the input files and set the output.

 ffmpeg -i video.mp4 -i audio.ogg video_sound.mp4

Extract audio track

If you just need to extract the sound, then you can.

 ffmpeg -i video.MOV -vn audio.ogg

Specify the format of the extracted audio track.

 ffmpeg -i video.MOV -vn -c:a flac audio.flac

Indicates the acceptable bitrate, by default 128k will be recorded.

 ffmpeg -i video.MOV -vn -c:a flac -b:a 192k audio.flac

Making a slide show of pictures

The same case, when it was smooth on paper. In practice, you have to walk around the rake, pushing through the inconsistency of formats, codecs, sizes and orientation of photos.

 ffmpeg -r .3 -pix_fmt rgba -s 1280x720 -pattern_type glob -i "*.JPG video.mkv

Some explanation is required.

-r number - frame rate per second.
-pix_fmt - Pixel format, list from the ffmpeg -pix_fmts . Not with all formats it turns out to set the desired frame size.
-pattern_type glob - To use a pattern match as in a command shell. An alternative is to use the C printf format, for example image%03d.png for all image0001.png , image0002.png , etc.

Change video stream

Suppose you do not need the entire video file, but only a part of it. This command cuts 10 seconds of video starting from the first minute.

 ffmpeg -i video_full.m4v -c:av copy -ss 00:01:00 -t 10 video_short.m4v

How to improve the quality of audio or video streams? To do this, use the key bit- -b .

 ffmpeg - video.webm -c:a copy -c:v vp9 -b:v 2M final.mkv

Screen capture

To capture the screen, an x11grab device is x11grab , and ffmpeg should be built with the --enable-x11grab .

 ffmpeg -f x11grab -framerate 25 -video_size 4cif -i :0.0 out.mpg

-video_size word - Capture size, cif = 352x288, 4cif = 704x576. Read more in info ffmpeg-utils .

Bonus track

For automatic photo processing is convenient to work with the program ImageMagick . Change the size of all photos in the folder.

 mogrify -resize 60% *.png

Accurate image sharpening, like Smart Sharpen using a Perl script that uses convert and composite from the ImageMagick toolkit .