Digital Video File Formats Explained and Defined

Digital Video File Formats 

The wonderful world of digital video is drowning in a sea of alphabet soup. Do you get frustrated not knowing an .avi from an .flv?

If you want to know why there are so many confusing formats, blame the fact that everybody feels the need to have their own.  Each development or manufacturing company, each standardizing organization, and every combination hereof, all have to come up with their own proprietary software codes and methods.

On one hand, that gives you lots of choices. On the other hand, it makes things confusing and sometimes prevents stuff from WORKING!

Fortunately, that has improved over the years.   There are lots of friendly alliances and most folks work with a goal of compatibility and universal platforms in mind. Customer demand helped that happen.    Even so, not all formats are suitable for Internet Video, where file sizes need to be small. New HD formats are great for home entertainment, but are way too big for the web.

Here is a list of common formats for video, still images, and audio.

Let’s start with the letter A:

AVCHD: Stands for Advanced Video Codec High Definition. This is a high end consumer home electronics format developed by Sony and Panasonic for HD home theater systems. It’s not a web format.

Video editing software applications are slowly adding this format to their repertoire.

AVCHD uses MPEG-4 H.264 encoding which is standard for many video formats. Blu-ray players will eventually play this format too and it will become a standard in home theater systems.

.AVI This is a format for motion picture files developed by Microsoft that conforms to standards set by Microsoft Windows Resource Interchange File Format (RIFF). .AVI stands for Audio Video Interleaved and works with applications that capture, edit and playback audio and video, like Windows Movie Maker. Because it is windows-based, .avi format is virtually universal. The problem with avi is that not all avi files are actually the same. AVI contains multiple streams of different type data, including a control track and separate video and audio streams. AVI is what’s known as a container format. If what is IN the container is drastically different from your video player, an avi might not play for you.

As with all Microsoft products, this format is extremely common. .AVI is known for good video quality and commonality. AVI creates relatively large compressed files that retain high quality. For help in understanding Microsoft windows better, the microsoft md 100 exam can provide a good background in how to navigate and maintain windows needs.

DivX A popular video compression software known for being able to squeeze an entire movie onto one CD. DivX has the reputation of being powerful and stable, providing excellent quality and high compression. This software has been developed jointly by the DivX Networks and the open source community, which many people feel is the best method of software development. Lots of brains with one goal. The hot new thing in DVD players is that some now play DivX files in addition to MPEG-2 files.

You can download a free trial of the DivX compression software at http://www.divx.com/ The site claims its been downloaded over 220 million times. According to their mission, DivX is more than compression software. It’s a global community informed by creativity and passion for all that is possible with digital media, and that community is growing in strength and number every day.

Some say DivX become the Internet’s de facto distribution standard, and it has the advantage of allowing viewers to skip around while watching. Some buffering is to be expected, but it works just like a video on your hard drive – you can forward, rewind and pause whenever you want to instead of being restricted to watching it from start-to-finish as it downloads.

Another popular feature about DivX is the open platform. Anyone can design plug-ins for DivX Connected using its open source SDK. It uses the Gecko rendering engine; the framework behind Firefox.

The many formats with PEGS.

How many PEGS does one need?

In the world of digital video, there are lots of pegs… JPEGS, MJPEGS, MPEG-1, MPEG-2, MPEG-3, MPEG- 4 and variations of, on and on and on. Each one of these is a distinct file format with different uses. Here is an in-depth explanation of each.

Good Ole JPEG

JPEG is thought by many to be the name of a file format, but it actually stands for a group which devises standardizing specifications for digital images. JPEG stands for the Joint Photographic Experts Group and the well known JPEG format is commonly used for still images.

The most common file extension for this format is .jpg, though .jpeg, .jpe, .jfif and .jif are also used just to make it all more confusing! Many of these differing file extensions indicate slight variations of the format.

JPEG/JFIF is the format most used for storing and transmitting photographs on the Internet. For digital stills, most people consider JPEG far superior to GIF, which has color limitations.

JPEG is also preferred online to PNG, which produces much larger image files.

Even though it has great color reproduction, the JPEG compression algorithm is not well suited for line drawings or text, the kind of stuff that makes up logos. PNG and GIF formats are preferred for these types of images.

JPEG Moves

MJPEG is the motion version of the JPEG format. The added M stands for motion and an MJPEG is a series of still JPEG images blending together to form a moving image.

MJPEG is best suited for broadcast resolution video, which is higher than Internet resolution. MPEG is not good for images less than TV resolution. MJPEG doesn’t work at all good on computer progressive scan monitors. MJPEG is usually used for short files made by a digital still camera, not a standard video camera.

MORE PEGS FROM OTHER EXPERTS

Not to be confused with JPEG and MJPEG, you might also recognize MPEG as a format, but the acronym MPEG stands for another organization that develops standards defining formats.

MPEG refers to the Motion Picture Experts Group. This international group was established in 1988 to develop standards for digital audio and video formats, but they’re not the only group doing so as anyone who studies digital video files formats knows.

You’ll be glad to hear that many of these groups collaborate.

Four different MPEG standards developed by the group and bearing their name are now in common use on both the internet and home and professional video equipment. Each format has a specific application and bit rate.

MPEG1. This format is often used in digital cameras and camcorders to capture small, easily transferable video clips. It’s also the compression format used to create Video CDs, and is commonly used for posting clips on the Internet. The well-known MP3 audio format (see definition below) is part of the MPEG-1 codec.

To be specific, MPEG-1, Audio Layer 3 is the popular audio format known as MP3.

MPEG-1 continues to be a useful format. As cheaper and more powerful consumer decoding hardware became available, more advanced formats such as MPEG-2 and MPEG-4 were developed.

Those newer formats were more complex and required more powerful hardware, but as with all advancements, the formats also achieved greater coding efficiency. This gives you, the consumer, better quality in ever smaller and smaller file sizes.

MPEG-2 is the format used for standard DVD players and digital broadcast television coming from your cable company.

Commercially produced DVD movies, home-recorded DVD discs, and most digital satellite TV broadcasts employ MPEG2 video compression to deliver their high-quality picture. If you rent a movie on DVD, it’s MPEG-2.

MPEG2 is also used by TiVo-based hard disk video recorders. It can rival the DV format when it comes to picture quality. Because MPEG2 is a “heavier” form of compression that removes a larger portion of the original video signal than DV, however, it’s more difficult to edit with precision so it is rarely used with video editing software.

The MPEG2 codec allows for selectable amounts of compression to be applied, which is how home DVD recorders and hard disk video recorders can offer a range of recording speeds. The faster your recording, the greater your quality.

Main characteristics

MPEG-2 is widely used as the format of digital television signals that are broadcast by terrestrial (over-the-air), cable, and direct broadcast satellite TV systems. It also specifies the format of movies and other programs that are distributed on DVD and similar disks. As such, TV stations, TV receivers, DVD players, and other equipment are often designed to this standard.

With some enhancements, MPEG-2 Video and Systems are also used in some HDTV transmission systems.

MPEG-4.A flexible MPEG container format used for both streaming and downloadable web content. It’s the video format employed by a growing number of camcorders and cameras and it is highly recommended. MPEG 4 has become one of the single most common web video formats as it is one of the most universal when it comes to playback.

In fact, when uploading video files to YouTube, they recommend you use MPEG-4 format. YouTube accepts multiple formats, then converts them all to .flv for distribution, or at least they used to run exclusively Flash video for playback but all that has been evolving to include more MPEG4 for HTML5. .

MPEG-4 is considered by many to be the standard for multimedia and web compression and is the most used codec today. It retains excellent picture quality.

This highly advanced compression software uses object-based compression where individual objects are tracked separately and compressed together.

MPEG-4 is still a developing standard and is divided into a number of parts.

Unfortunately the companies promoting MPEG-4 compatibility do not always clearly state which “part” level compatibility.

The key parts to be aware of are MPEG-4 part 2 (MPEG-4 SP/ASP, used by codecs such as DivX, Xvid, Nero Digital and 3ivx and by Quicktime 6) and MPEG-4 part 10 (MPEG-4 AVC/H.264, used by the H.264 codec, by Nero Digital AVC, by Quicktime 7, and by next-gen DVD formats like HD DVD and Blu-ray Disc).

Hopefully, you will not get tripped up by the multi-faceted nature of MPEG-4. Just be aware if something doesn’t work when it logically should, this might be the issue.

The H26L Series of Codecs

Now, we’ll talk about the H.26L series of codecs developed jointly in a partnership of the Video Coding Experts Group, (VCEG) and MPEG, the Motion Picture Experts Group. MPEG) Those two groups based the H.26L series on earlier developmental work from the International Telecommunications Union based in Geneva, Switzerland.

The current version of the series, H.264, is an important element of many software applications. H.264 is quite popular, versatile and high quality in many respects.

Like all things, H.264 has evolved from earlier versions. H.261 was the first version designed for transmission of video over Integrated Services DigitalNetwork (ISDN) lines on which data rates are multiples of 64 kbit/s.

H.261 was considered a break-through technology. The basic processing unit of the design is called a macroblock, and H.261 was the first standard in which the macroblock concept appeared.

One advantage of H.261 was an effective post-processing technique that became a key element called the de-blocking filtering. This reduced the appearance of annoying block-shaped artifacts caused when motion is compressed. Such block-like pixilations are probably familiar to almost everyone who has watched digital video.

Deblocking filtering has since become an integral part of the most recent standard, H.264 (although even when using H.264, additional post-processing is still allowed and can enhance visual quality if performed well).

H.261 has become essentially obsolete, although it is still used as a backward-compatibility mode in some video conferencing systems and for some types of internet video.

H.263 is the second in this series designed by the ITU-T. H.263 came in 1996 as a low-bitrate compressed format for video conferencing and internet transmission.

The next enhanced codec developed by this consortium is the H.264 standard, also known as AVC and MPEG-4 part 10. It was completed in May 2003. This version is the most up-to-date and H.264 provides a significant improvement beyond H.263. Most new videoconferencing products now include H.264 but remain compatible with H.263 and H.261.

Digital Audio

No list of digital file formats would be complete without audio formats and the glorious MP3, which is actually MPEG-1, Audio Layer 3, but who’s counting?

MP3 is by far the most popular codec for storing and transferring music, made ubiquitous by iPods and other MP3 players.

To compress the file, MP3 removes frequencies judged to be essentially inaudible. For most human ears, MP3 manages to deliver near-CD sound quality in a file that’s only about a tenth or twelfth the size of a corresponding uncompressed WAV file.  I know audio aficianados who would dispute that, but that’s what the data shows.

When creating an MP3 file, you can select varying amounts of compression depending on the desired file size and sound quality.

mp3Pro

An updated version of the original MP3 codec. Small, low-bitrate mp3Pro files contain much more high-frequency detail than standard MP3 files encoded at similar low bitrates.

The high-frequency portion of the audio signal is handled by an advanced and extremely efficient coding process known as Spectral Band Replication (SBR), while the rest of the signal is encoded as a regular MP3.

That means that when you play an mp3Pro file on non-mp3Pro-compatible software, it’ll play, but you’ll only hear the non-SBR-encoded portions. This means you’ll lose the highs altogether. Bummer.

The solution is to use a fully compatible audio program, such as Windows Media Player and mp3Pro files will deliver great sound quality with extremely low bitrates.

Wave at Me Baby!

.WAV file extension identifies a standard audio format for Windows operating systems that’s used for storing high-quality, uncompressed sound. WAV files are large since they are uncompressed. They provide extremely high quality audio.

.WAV contains CD-quality (44.1 KHz/16-bit) audio signals and require relatively large amounts of memory – roughly 10 MB per minute of music.

WAV is what’s known as a container format, or one which holds different kinds of data within its file. Container formats are gaining in popularity because of their multimedia applications, as well as their cross-platform compatibility. For example, a single container file can hold chapter information, hyperlinks and subtitles, as well as different kinds of codecs that enable various types of players to read the file. This all makes it more convenient for the user.

Windows Media Audio, file extension .WMA

Like .wav, Windows Media Audio is a Microsoft product so is one of today’s most pervasive Internet audio formats. Though not as popular as MP3, proponents of the lossy compression format claim it outperforms MP3 in sound quality, particularly with files encoded at lower bitrates such as 64 or 96 Kbps.

This performance advantage makes it handy for applications like portable digital audio players, where total play time is limited by a finite amount of internal memory. Although the technical specs will put WMA ahead of MP3, many human ears could never tell the difference.

The Windows Media Audio format features built-in copy protection abilities, unlike MP3. Windows Vista, the new Microsoft operating system, contains built in support for WMA encoding so you can easily create WMA music files. No doubt Mr. Gates wants WMA to be even more common than it is.

WMV (Windows Media Video)

A .wmv file indicates one compressed using Microsoft’s proprietary lossy compression format for motion video. Windows Media Video is used for both streaming and downloading content via the Internet. Microsoft’s Windows Media Player, an application bundled with Windows Vista operating systems, lets you play back and manage a range of audio and video file types, including WMA and WMV.

.MOV: This is the file extension used to identify an Apple Quick Time Movie. Quicktime hasn’t been a Mac-only program for quite some time. Quicktime versions exist on almost all PCs. Some people argue that Quicktime is far superior to similar Windows based applications.

Xvid is an open-source lossy video codec based on MPEG-4. It was developed in response to DivX, and received its name from the backwards spelling of DivX. Xvid compresses a great deal of video content into relatively small files, and retains a reasonably good video resolution. It can be used with several different operating systems, and is a popular choice for transferring video over the Internet.

If you see a video file on your computer labeled MSWMM, be aware that this is a windows movie maker project file and not a video or movie file designed for sharing. MSWMM will only play within Movie Maker. When you want to save your movie to share it, that is the time to use Movie maker to convert it into a more universal format, such as .avi or .wmv. This confuses many people. No matter what video editing software you use, a project file is designed for working on within the editing program. You must convert the project file to watch it on any other player.

For even more information on digital video file formats you can read this companion post.

Or, click here for a third post explaining FLASH Video format.

I hope this extensive post on digital video file formats and audio formats helps you! Thanks for reading Video Production Tips!

Lorraine Grula