24 Jan 2010

Video Format & Codec

This section is to help you understand codecs, video file formats, and how these formats are used in the day-to-day multimedia application.

Short for compressor/decompressor, codecs are the engines that power the software applications that compress video files. After you capture your video footage, the first step to delivering the video content is to compress it. In order to compress properly, it is important to understand how a codec works by explaining some basic compression concepts.

Compression is like making orange juice concentrate. Fresh oranges go in one end and concentrate comes out the other. The concentrated orange juice takes up less space, is easier to distribute, and can be easily reconstituted by the consumer.

One second of uncompressed video is roughly 30 MB. It is expensive to store, manage and deliver large amounts of data. Codecs help solve this problem by compressing video to smaller, more manageable sizes while still maintaining quality. The smaller files require less hard disk space, less memory to run, and less bandwidth to play over networks or the Internet.

Video File Formats
A file extension is a generally a three letter suffix to a file name that follows a period. In the file sales.mov, sales is the file name and .mov is the extension. The extension tells the operating system which program to use to interpret the file.

Advanced Streaming Format (ASF)
Stands for Advanced Streaming Format. stores audio and video information, and it is specially designed to run on networks like the Internet. ASF is a highly flexible and compressed format that contains streaming audio, video, slide shows, and synchronized events. When you use ASF files, content is delivered to you as a continuous flow of data. When an AVI file is compressed and converted to an ASF file, the file begins playing after only a few seconds.

Advanced Stream Redirector (ASX)
Advanced Stream Redirector files are text files used for redirection to MS Windows Media Player ASF files. These files contain media and server information but no actual video or audio. ASX files can be distributed as attachments or links. When you open an ASX file, the file opens the referenced movie in your media player, making it appear as though the entire file has been downloaded.

Audio Video Interleaved (AVI)
Audio Video Interleaved is a bitmap-based format for the Windows platform defined by Microsoft. It is the most common format for audio/video data on PC and an example of a de facto (by fact) standard. Raw AVI from video capture is a great place to start for compression, but too large for effective use across the Internet.

Digital Video (DV)
To process and store video on a computer, it must first be converted to a binary format. Most digital video cameras are capable of outputting video directly to a hard drive in this format via IEEE 1394 interface. DV is a good format for compression and editing application input, but file sizes are too large to deliver effectively over the Internet.

Macromedia Flash Video (FLV)
This is a Macromedia Flash video file in which the video and audio are compressed. When an FLV clip is added to a Flash timeline, the video is not compressed a second time, so the import is considerably less time consuming. FLV files can be created using Flash with Sorenson Spark or Sorenson Spark Professional (Pro). Spark Pro has the added advantage of being able to batch process entire directories of video to FLV or SWF format for later use at a higher quality and smaller file size than are possible using the standard version of Sorenson Spark.

QuickTime Movie (MOV)
All QuickTime Movies are associated with the MOV file extension. This extension works on Win 95/98/2000/NT/XP, Mac OS Classic and X. It also supports over 200 media types (Photoshop, GIF, JPEG, etc.) in addition to QuickTime movies. One major advantage of working in the QuickTime environment is its free server.

Moving Picture Experts Group, Level 4 (MP4)
MPEG-4 was defined using the standards for encoding video in a digital compressed format as specified by the Moving Picture Experts Group (MPEG). It supports video, audio, and system components that are compliant with the International Organization for Standardization (ISO) MPEG-4 de facto standards. MPEG-4 open standards are a set of specifications used to build products for production, encoding and delivery of audio/video content over many kinds of networks to a variety of clients such as personal computers, wireless devices, Web browsers and more.

Device manufacturers prefer using MPEG-4 because the open architecture and codec do not lock them into specific formats or players. Instead of having to develop for three or four separate formats, which is logistically difficult and costly, providers can build on the MPEG-4 single format.

Real Networks Files (RA, RM, RAM)
Real Networks content is software developed by RealNetworks that streams live or pre-recorded audio/video to a client, such as a Web browser, by decompressing it dynamically so it can be played back in real time. Delivering Real Networks content requires use of RealSystem Server Basic (free), Plus, intranet or Professional software. The RealSystem Server Basic allows for up to 25 concurrent viewers. As your requirement for simultaneous viewers increases, so does server price.

Macromedia Flash .FLA File Published for the Web (SWF)
When a Macromedia Flash MX .FLA file is published for the Web, it takes on the SWF extension. While normally associated with vector graphics and audio, Macromedia Flash MX now supports embedded video. An advantage of working with the Flash player is its widespread distribution and the ability to include powerful programming elements using ActionScript. SWF files can either be created individually in Macromedia Flash MX using Sorenson Spark or in bulk as an automated process using the Spark Professional video codec in Sorenson Squeeze for Macromedia Flash MX.

MS Windows Media Audio (WMA)
MS Windows Media Audio is an audio codec designed by Microsoft for use with streaming content at CD quality. It is designed to resist data loss that can cause signal degradation and can improve download times for audio.

MS Windows Media File (WMV)
This an MS Windows Media file with audio and/or video. It is used to download and play files or stream content. The WMV format is similar to the ASF format. See ASF file documentation for more information about its capabilities.

The 3rd Generation Partnership Project (3GP, 3G2)
This is the MPEG4 based video format used in mobile terminals, like cell phones.

CD Audio Track (CDA)
CD Audio Track, audio files that are on CD media. You can play .cda files only from a CD-ROM. Often the CDA tracks are ripped to WAV or MP3 files.

To take off the audio or video from a CD or DVD. Often CD Audio is "ripped" to MP3 WAV OGG VQF files or DVD video ripped to AVI MPEG DivX files.

A powerful MPEG-1/MPEG-2 video converter for Mac OS X 10.2 or later. It uses QuickTime, MPEG, MOV, SMP, AltiVec, YUV, Cocoa, Quartz, XML and other amazingly great acronyms and buzzwords. It's also fast, high quality, and integrates extremely well with 3ivx D4 4.5, allowing it to perform automated 2-pass encoding with 3ivx.

A new format for digital video, much like MP3 is a format for digital music. DivX is the brand name of a patent-pending video compression technology created by DivX Networks, Inc., The DivX codec is based on the MPEG-4 compression standard. This codec is so advanced that it can reduce an MPEG-2 video (the same format used for DVD or Pay-Per-View) to ten percent of its original size.

Digital Theater Systems Digital Sound, A product of DTS Inc., DTS is a multichannel audio compression format similar to Dolby Digital used in DVD-video discs, DVD-audio, 5.1 channel audio CDs, and some movie theaters. DTS differs from Dolby Digital in that it generally uses higher data rates and many have the opinion that DTS is better quality. DTS can only be on a DVD-video disc if accompanied by a Dolby Digital or LPCM track (for North America) or mpeg audio and LPCM (European Community) to ensure compatibility, because DVD players are only required to decode those standards in those regions.

Digital Video, video captured to a PC from a digital camcorder, often through Firewire. There are two methods of storing DV video data, referred to in this article as type-1 and type-2. Both are stored usually in AVI files.

DVD once stood for Digital Video Disc or Digital Versatile Disc, but now it just stands for DVD -- the next generation of optical disc storage technology. DVD is essentially a bigger, faster CD that can hold cinema-like video, better-than-CD audio, and computer data.

An .m3u file is a special type of metafile playlist that is used with MP3 files that have an .mp3 file extension. The .m3u file includes information about the location of the .m3u file on the computer and the properties of the file. An .m3u file is similar to the ASX playlist files.

Extended VCD, XVCD has same features as VCD but it is possible to use higher bit rates and higher resolution to get higher video quality. XVCD is basically everything that uses MPEG-1 video, is not within the VCD standard, and burned in "VCD" Mode on a CD-R or CD-R(W). XVCD can be played on some hardware VCD or DVD players and many computers with appropriate software.

Is an ISO MPEG-4 compliant video codec. It's not a product but an open source project which is developed and maintained by people around the world.

An MPEG-4 toolkit that supports MPEG-4 Video, MPEG-4 Audio and the MP4 File Format.

Stands for Advanced Audio Coder. An audio-encoding standard for MPEG-2 that is not backward-compatible with MPEG-1 audio.


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MiLd™ said...

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