Very often it is useful to compress video files to send them faster via Email or to upload them on the internet to sites such as YouTube or, again, to view them on mobile phones. Probably, however, this topic has gone out of fashion given the large amount of online services that allow you to send files without size limits, without having to clog the email to someone.
It certainly doesn't make sense to compress a DVD because in that case you simply need a program to convert DVD to Divx.
Converting then becomes the easiest way to compress video files and reduce their size.
READ ALSO: Programs to compress videos and view them on mobile or tablet
However, for completeness of information, compressing videos and reducing the size of an AVI file is still a useful computer activity that can be easily done.
The bad news is that video compression has side effects on the visual quality of the video.
Like the audio file, even the video files, if compressed, lose image quality with the formation of blocks of pixels called artifacts (they are noticed when the image changes quickly and remain squares of color still for a few fractions of a second).
The good news though is that video compression can be done for free and here we see the two most used and popular ways, therefore probably the best and easiest.
The most used video file is the Avi file and this is what this guide refers to.
1) Video compression with VirtualDub
VirtualDub is a free open source program already encountered in the video editing article.
The best features of VirtualDub are its speed in processing videos and the number of codecs that can be used.
Codecs are nothing more than programming codes that contain instructions for compressing and decompressing audio and video files so that they do not take up too much space.
VirtualDub, by default, has very few integrated codecs but you just need to download them separately to have them incorporated into the program.
For common and basic use, just download and install the XviD codec that allows you to compress video files in Avi.
Then start VirtualDub and load the video file you want to compress (File - Open Video File).
After the video has opened in the VirtualDub player, on the toolbar, click on Video -> Compression .
In the drop-down menu select video compression and choose the MPEG-4 XviD Codec format, press on Configure, press on the target button and set the bitrate to a value of 300 kbps.
This setting is vital because, just as the quality of an image is based on its resolution, the quality of an audio or video file is calculated with the bitrate .
In this regard, you can make several attempts and check if the quality lowers too much until you find a decent balance between compression and video and audio quality.
Still looking at the line where target bitrate is written, you can press the calc key to change the size of the video file measured by hand in kbytes.
A high value on Target size brings an increase in the bitrate and vice versa.
I would not touch the other values of this window even if doing tests will not cause any damage.
At the bottom you can set the bitrate values for audio but here I would not go below 128 kbps for MP3 but it depends on how important good listening is considered.
To start compression, click File - Save as AVI and choose where to save the video (be careful not to overwrite the original).
VirtualDub is considered the best software to manipulate videos, however it is not the simplest also because you have to download the codecs separately and, those who are not familiar with these objects may find themselves in difficulty.
So, let's see another excellent program, of the same level but simpler to use like Avidemux
2) Avidemux is another free software to edit video files which is available for Windows, Linux and Mac.
Avidemux is also in Italian and, among other functions, it has a tool called a calculator which is used to calculate the compression ratio based on a final size which is a unit of measurement understandable to all.
After installing it, go to File -> Open, load the video you want to compress and set the codec to use for both video and audio from the drop-down menus on the left.
Then choose, in the case of Avi or divx video, the MPEG-4 ASP (Xvid) codec and for MP3 audio.
In the last menu, set the format to AVI .
Now click on the Configure button below the video codec selection menu and use the cursor to choose the desired quality.
In this case I would set an average value but here too you can test and it always depends on the video to be converted.
Then go to Tools -> Calculator, select Custom from the drop-down menu where Support is written and write a value for the new size of the video file.
By saving, you get a copy of that compressed video and the chosen size in MB.
3) Third program to compress an AVI is ReComp
Avi ReComp does just that and does it well, it's a free and easy to use program.
The beauty of this program is that it requires no configuration .
All you have to do is choose the source avi file whose size you want to reduce, select where to save the new version and choose a new format.
The problem is just choosing the right file size, neither too large nor too small.
The program itself suggests ideal compression for a file and other advanced options.
With Recomp you can also crop the video, activate or deactivate the subtitles, display a logo and remove black borders.
Video compression can also be done on Windows Movie Maker which in Vista and Windows 7 allows you to compress videos in WMV format and send them via Email in one click.
