FFMPEG is a tool for handling and editing multimedia stuffs. It supports
all the popular media formats and has a lot of cool options and
features. You probably have ffmpeg installed already in your machine if
you are using some video or audio editing tool. But if you dont, you
can install ffmpeg easily by installing libav-tools. In Ubuntu and other
Debian-based distros, the installing command is:
sudo apt-get install libav-tools
Here are some small tricks with ffmpeg that I frequently use when I need a fast tool to do some simple multimedia editing tasks:
1 - Convert an audio file to another format
When you need to convert an audio file to another audio format, like when you want to have an .ogg file to change the login sound of Ubuntu, ffmpeg is the fastest tool you can use. The command to convert an audio file to another formate with ffmpeg is:
ffmpeg -i input.mp3 output.ogg
2 - Convert a video file to another format
The command to covert a video file to another format is quite similar,
but you can also use an additional option to convert the video
resolution too:
ffmpeg -i input.avi -s 800x600 output.flv
In this command, the -s parameter means the size of the output video and
800x600 is the its resolution. You can omit this option if you want to
keep the original resolution.
To know more about the formats supported by ffmpeg, please check
this link.
3 - Crop an audio file
The command to crop an audio file with ffmpeg is:
ffmpeg -acodec copy -i input.mp3 -ss 00:00:25 -t 00:02:00 output.wav
In this command "-acodec copy" is to keep the original sound, "-ss
00:00:25" is to tell where to start cropping and "-t 00:02:00" is the
length of the cropped output file. You can change the time variables as
you prefer.
4 - Crop a video file
The command to crop a video file with ffmpeg is somehow similar:
ffmpeg -vcodec copy -acodec copy -i input.avi -ss 00:00:25 -t 00:02:00 output.flv
The only change in this command is that you need to define the video
encoder when cropping video files, the usual option is "-vcodec copy" to
keep the original video.
5 - Extract the audio part from a video
You can use ffmpeg to extract audio from a video file. However, you will
need to identify the format of the audio in the video file first. The
tool to do this task is ffprobe ( which also comes within the
libav-tools package). To identify the audio format of a video file, the
command will be:
ffprobe videofile.avi
Here is the sample output of this command. The highlighted part is the
audio properties of the video file, the audio format here is .aac:
After you know the audio format of the video file, the command to
extract the audio part will be (I use the sample file aa.mp4 here):
ffmpeg -i aa.mp4 -vn -acodec copy output.aac
6 - Extract images from a video
If you want to extract images from a video with ffmpeg, the command is:
ffmpeg -i video.mp4 img%d.jpg
This command will create 25 images for every second of the input video.
The output images will be named img1.jpg, img2.jpg, img3.jpg ..
If you want to change the frame rate into 10 images for every second,
you can use the "-r" option. The command to extract 10 images for each
second of the input video will be:
ffmpeg -i video.mp4 -r 10 img%d.jpg
If you want to extract images from a certain time, you can use the "-ss"
and "-t" options as you use for cropping audio and video files. The
command to extract 15 images for each second of the video and the
process starts at the 30th second and ends at the 40th second will be:
ffmpeg -i video.mp4 -r 15 -ss 00:00:30 -t 00:00:10 img%d.jpg
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These are 6 small tricks that I often use with ffmpeg. But as I have
said, ffmpeg has a lot of options and features (I myself dont know all
of them). So if you really want to know everything about ffmpeg, you can
check
its official document (note: its a huge wall of text).
