There are many video file formats to choose from when creating video streams. The most common formats are:
- Windows Media
- MPEG (in particular MPEG-4)
- Shockwave (Flash)
Let me explain now couple of things about these video formats, most of them commonly used by the digital media industry.
Windows Media files have the extensions: .asf, .asx, .wma, and .wmv.
–> ASF (Advanced Streaming Format) is a streaming media format developed by Microsoft. ASF files can contain video, audio, slide shows and synchronized events. ASF files are very similar to WMV files. A variety of codecs can be used to create ASF files. The end user must have the same codec installed to view the file. To stream an ASF file, use an ASX file.
–> ASX (Advanced Stream Redirector) is a special type of file which works closely with Windows Media ASF files .The purpose of an ASX file is to start the ASF file streaming.
The ASF file is the actual media file, containing video, audio, etc. The ASX file is a metafile. Metafiles provides information about files. ASX files are plain text files used to describe multimedia content and include a reference to an ASF file.
–> WMA files (Windows Media Audio) are very similar to WMV files except they contain audio only. Is designed to handle all types of audio content. The files can be highly compressed and can be delivered as a continuous flow of data (online ). WMA files can be of any size, and be compressed to match many different bandwidths (connection speeds).
–> WMV files (Windows Media file with Audio/Video) are very similar to ASF files. WMV is designed to handle all types of video content. You can use WMV files to provide downloadable or streaming video.
Other Windows Media formats, but not such popular:
–> WMVHD stands for Windows Media Video High-Definition. WMVHD files are like other Windows Media files except they have a higher resolution, leading to clearer, sharper movies.
–> WAX (Windows Media Audio Redirector) files are much the same as ASX files, but intended to describe audio files (.wma files).
–> WMP (Windows Media Player) files and WMX are reserved file types for future use by Windows.
Windows Media has the advantage of being backed by the giant Microsoft. Updates to the Windows Media Player are easy and most people who run Windows on their computer have the correct player. WM files are relatively high quality and low size. On the other hand, Microsoft is frequently changing formats and standards. As a video producer, it can be difficult sometime keep up-to-date with the latest version. Also, Microsoft is a very proprietary format, and any platform other than Windows/IE may have problems.
AVI files have the extension: .avi.
The AVI (Audio Video Interleave) format was first developed by Microsoft for Windows computers as a response to the rival Quicktime format. The AVI format is supported by all computers running Windows (via helpers and plug ins), and by all the most popular web browsers. It is a very common format on the Internet, but not always possible to play on non-Windows computers.
It can use several compression schemes and is becoming very popular. Most digital video cameras shoot in .avi format. AVI files are limited to 320 x 240 resolution, and 30 frames per second, neither of which is adequate for full-screen, full-motion video. Video or audio producers use this format because it allows them to sell their products to the largest base of users.
RealVideo files have the extensions: .rm or .ram.
RealVideo was one of the first serious streaming video solutions. Real Media video images tend to be less sharp than other formats. Moving images are handled reasonably well but the finer detail can be easily lost. Overall, the image quality is perfectly adequate for most applications. A big disadvantage is the difficulty in downloading the free Real Media Player. Real Media maintain a commercial business model and they strongly encourage you to buy the full version.
This left many people over the Internet to become disillusioned with the format and its reputation has not held up well over recent years. But overall, Real Media solution remain one of the first and still most popular streamed media format. You can also use the files as non streamed format, but they are not so well designed for that. The .rm format allows streaming of video (online video, Internet TV) with low bandwidths. As a result, quality is often reduced.
RealVideo is ideal for transmitting live video over the Internet and uses a variety of data compression techniques.It works with both normal IP connections as well as IP Multicast connections.
Quicktime files have the extension: .mov.
Quicktime is a format which has been around since the beginning of video production. In many ways Quicktime is more complicated than Windows Media or Real Media. Quicktime advanced features allow you to create interactive video, panoramas, virtual reality settings and more. It is a good format with many unique features, even sometime it’s seems to be hard to make it work at his fullest potential.
Quicktime is supported by many editing, authoring and general interest applications. These file types are based on the Quicktime system. Its designed initially for the Mac platform but is now usable via a plugin and helper application on most other operating systems (including Windows systems). You can download the standard Quicktime player from Apple for free as well as get access to a host of resources. Quicktime has some great compression schemes which often make .mov files smaller without loss of quality. Of course, it can also be streamed.
QuickTime supports most encoding formats. In February 1998, the ISO standards gave Quicktime a big boost by deciding to use it as the basis for the new MPEG-4 standard.
MPEG files have the extensions: .mpeg or .mpg.
MPEG (Moving Picture Experts Group) produces better quality video than competing formats. This format can be decoded by special hardware or by software. MPEG achieves high compression rate by storing only the changes from one frame to another, instead of each entire frame. The video information is then encoded using a technique called DCT. MPEG uses a type of lossy compression, but generally imperceptible to the human eye. There are five MPEG standards being used or in development: MPEG-1, MPEG-2, MPEG-4, MPEG-7 and MPEG-21.
MPEG-1 provide a video resolution of 352-by-240 at 30 frames per second (fps). This produces video quality slightly below the quality of conventional VCR videos. Is designed for up to 1.5 Mbit/sec.
MPEG-2 offers resolutions of 720×480 and 1280×720 at 60 fps, with full CD-quality audio. This is sufficient for all the major TV standards. MPEG-2 is used by DVD-ROMs. Encoding video in MPEG-2 format requires significantly processing power. MPEG-2 is designed for between 1.5 and 15 Mbit/sec.
MPEG-1 and MPEG-2 are relatively simple video standards, but MPEG-4 introduces a new level of flexibility with an object-based approach. This allows for options such as interactive video and added media components (text, graphics, etc).
Many applications are available for creating MPEG-4. Because the standard is closely linked to the Quicktime architecture, applications which support Quicktime tend to support MPEG-4 (MPEG-4 can only be played in Windows Media Player with a special MPEG-4 decoder pack).
MPEG-7 is currently under development, is also called the Multimedia Content Description Interface. When released, the group hopes the standard will provide a framework for multimedia content that will include information on content manipulation, filtering and personalization, as well as the integrity and security of the content. Contrary to the previous MPEG standards, which described actual content, MPEG-7 will represent information about the content.
For MPEG-21 (Multimedia Framework), work has just begun. MPEG-21 will attempt to describe the elements needed to build an infrastructure for the delivery and consumption of multimedia content, and how they will relate to each other.
Shockwave (Flash) files have the extensions: .FLA, .FLV, .SWF, .SWT, .SWC.
–> FLA (Flash file) is the “master” document file for a flash project, i.e. the source file you work with in the Flash authoring program. These files can only be opened with Flash (not the Flash Player). To create the final product which is viewed by end users, export the appropriate file (usually SWF) from the FLA file.
–> FLV (Flash Video) – files are the preferred format for delivering video clips via Flash.
–> SWF (Flash delivery file) is the file that end users see. This is a compressed version of the FLA file which is optimized for viewing in a web browser, the standalone Flash Player, or any other program which supports Flash. This file type cannot be edited in Flash.
–> SWT (Flash template) allow you to edit and replace information in a Flash movie file; for example, a Flash button in which you can replace the text, links, etc.
–> SWC (Flash element) files have customisable parameters which allow you to perform various application functions.
Since the release of Flash Player 7, Macromedia Flash become a real force in the world of streaming video. From my point of view, for the moment, this is the format I recommend most strongly. But Flash is very expensive. To get the most from this format you need to own the Macromedia Flash MX Professional program. As well as being pricey, there’s a lot to learn.
But overall, Flash will give you power and flexibility beyond your wildest dreams! Custom controls and menus, interactive video and animations, advanced integration with web pages… the sky is the limit. Flash also has the huge advantage of having the most widely-supported cross-platform player. It is such a common plugin that almost everyone has it.
With Macromedia Flash you create digital media content, including graphics, animation, audio, video and interactive media. Flash content can be made either with the Macromedia Flash authoring program (known simply as Macromedia Flash) or third party applications such as Swish.
Flash content can be played back in two ways: SWF files are the normal way to deliver Flash on the Internet — the SWF file is embedded in a web page using special HTML code. The end user must have the Flash Player installed. Flash files can be also created as standalone executable files (.exe). These files run as a program in their own right and do not require the Flash Player. This option is useful for delivering content on CD or DVD.
Final Note: once you understood the differences between the different formats, it’s time to move on and learn about streaming video. This is one the most important step for you and it’s certainly the stage where most people kick-off.
Get the stream rate wrong and your video will not work properly. Get the codec wrong and you’ll hear the audio, but not see the video. And that’s just for the start… so keep reading!
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