What are video compressed files and codecs? (mpg, wmv, avi)

A video codec is a type of codec that compresses and decompresses digital video. Normally used compression algorithms involve a loss of information. The problem to be approached with the codec is that the video information is quite huge compared to what a normal computer can handle. Thus a couple of seconds of video in a barely acceptable resolution can occupy a respectable place in a typical media of storage (hard drive, CD, DVD) and management (copying, editing, visualization) can easily lead to outgrow of the computer or take it to its limit. Thus we preferred to build and occupy these algorithms compression and decompression in real time: the codec. Its purpose is to obtain a substantially less storage video information. This is compressed when saving the information to a file and decompressed in real time, while viewing. It is intended, moreover, that the process is transparent to the user, ie not to intervene or do as little as possible. There is a difficult balance between video quality, the amount of data required to represent (also known as bit rate), the complexity of the algorithms of encoding and decoding, robustness against data loss and errors, ease of editing, the ability to directly access the frames, and other factors.

What Player includes codecs?

Currently, there are hundreds of audio and video codecs in use. The vast majority of codecs have been created by independent companies, organizations or individuals. By default, the Windows operating system and the Player include many of the most popular codecs, such as Windows Media Audio, Windows Media Video and MP3, also Linux Ubuntu includes the most popular codecs.

However, you may sometimes want to play content compressed with a codec that is not included in your OS or the Player by default. In many cases, you can download the necessary codec from the web for free or by paying a fee. And in other cases, the player can use the codecs other breeding programs and creation of digital multimedia automatically installed on your computer.

Why a message indicating that a codec is missing on the computer is displayed?

If you receive a message indicating that a codec is missing on your computer, you are probably trying to play, burn, or sync a file compressed with a codec not included in your OS.

How can you find a codec?

If you know the name of the codec or its ID (known as a FourCC identifier for video codecs or WaveFormat identifier for audio codecs), try searching the Internet. Often, you can go to the manufacturer's website to download the latest version of a codec.

Some popular video codec

XviD codec

XviD is a free  and open source video codec, developed by programmers around the world that meets the standard MPEG-4 ASP. Works performing compressions at a loss, that is, those where the copy once compressed is different byte by byte from the original, and usually of lower quality (except some cases where, with the use of image filters, you can get fix certain defects a movie). Fortunately, using a good compression program and the appropriate settings, this loss becomes indistinguishable and can compress a DVD movie to the size of a CD with a similar quality.

DivX codec

DivX is a video codec based on the MPEG-4 standard. This codec can compress a video using algorithms with lossy compression, that is, the compressed copy is different byte by byte from the original, and usually of lower quality (there are exceptions, for example if we compress a poor quality video using filters image can be obtained a copy of better quality). However, the loss of quality in the compression process is usually minimal if proper techniques are followed, so we can compress a DVD movie in 1 or 2 CD with good quality.

x264 codec

x264 is a free and open codec to compress video tracks using the H.264 AVC (Advanced Video Coding) standard. H.264 belongs to MPEG, it is a standard. There are several implementations of this standard: Apple has one, Nero another, Microsoft another ... Free implementation  is x264. We can find this codec in two versions, one of VfW (Video for Windows), which allows using the codec in any compression program that supports codecs (eg VirtualDubMod), and another in form of command line interface, to which, you can add some graphical interface that facilitates its use (as MeGUI).

Some popular video formats

Digital videos can be saved in different file formats. Each corresponds to a specific extension of the file that contains it. There are many types of video formats. Here are some of the most commonly used. Also each file type at all times supports different compression codec.

AVI (Audio Video Interleaved)

Is the standard format for storing digital video. When video is captured from a digital camera to your computer, it is usually stored in this format with the DV (Digital Video) codec. The AVI file can contain video with excellent quality. However the file size is always very high. It supports different compression codecs like Cinepak, Intel Indeo 5, DV, etc. Codecs with more compression capability and acceptable quality are DivX and XviD. The AVI format can be viewed with most players: Windows Media, QuickTime, etc. It is not recommended post them online in this format because of its big weight.

MPEG (Moving Pictures Expert Group)

It is a standard format for digital video compression. They are file extension  .mpg or  .mpeg. It supports different types of compression codecs: MPEG-1 (more oriented Web) (CD quality), MPEG-2 (DVD quality), MPEG-3 (oriented MP3 audio) and MPEG-4 (MP4). They can be played using Windows Media Player and QuickTime.

MOV (http://www.apple.com/es/quicktime/)

It is the audio and video format developed by Apple. It uses a proprietary codec versions evolving fairly quickly. This type of file can also have extension  .QT. We recommend using the QuickTime player. There is a free version of it that can be downloaded from the Internet. It is ideal for publishing videos on the Internet at fair quality / weight. Supports streaming.

WMV (http://www.microsoft.com/windows/windowsmedia/es/)

It has been developed by Microsoft. Uses the MPEG-4 codec for video compression. You can also have extension .ASF. You can only view with an updated Windows Media Player 7 or higher. This application is integrated into Windows. It is ideal for publishing videos on the Internet for reasonable quality / weight. Supports streaming.

FLV (http://www.adobe.com)

It is a format used by Adobe Flash Player to view video on the Internet. Uses the Sorenson Spark codec and the On2 VP6 codec. Both allow for high visual quality with low bitrates. They are  .flv extension files.
They can be played from different local players: MPlayer, VLC media player, Riva, Xine, etc. Recommended option for the web because of its accessibility. When viewed using Flash Player is accessible from most web browsers and operating systems. The most popular video repositories on the Internet use this format for distributing videos: YouTube, Google Video, iFilm, etc. It allows you to configure various video parameters to achieve acceptable quality / weight. Supports streaming.


WebM is an open and free multimedia format developed by Google and designed to be used with HTML5. It is a free software project under a license similar to the BSD license. It consists of VP8 video codec (originally developed by On2 Technologies) and Vorbis audio codec within a Matroska media container.


3GP is a container format that was used by mobile phones to store information from multiple media (audio and video). This file format created by 3GPP (3rd Generation Partnership Project), is a simplified version of "ISO 14496-1 Media Format", which is similar to Quicktime format. 3GP saves video as MPEG-4 or H.263. The audio is stored in the AMR-NB or AAC-LC formats.

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