A 'co'mpression / 'dec'compression algorithm, used to take a raw stream of audio and/or video data and make it smaller by removing elements that are deemed unnecessary, and later to take the compressed stream and restore the original version so that it can be replayed on a display and/or sound system. Some codecs attempt to only remove elements that the average person would never miss, while others will notably reduce the image or sound quality, usually in order to make the content as small as possible for transmission over slow or low bandwidth connections. Codec selection is usually based on what is more important: quality or size/speed of the transmission.
The outer shell of a media file that organizes the stream(s) that it carries. Most video files have one video data stream and one audio data stream, but can contain multiple audio streams (possibly in different languages, or to support special surround-sound systems), or even additional video streams (to support watching the same program from multiple angles). The container format of a file is usually directly connected to the file extension or MIME type (e.g. Quicktime MOV, RealMedia RM, MPEG, MP4, Windows AVI, Windows WMV).
Note that a particular container format may support several different encoding formats, and no container format can handle every possible encoding format. Thus, for example, you can have two different MOV files, one of which plays just fine on a computer, while the other fails to play, due to that computer having a codec for the encoding format of the first file, but no matching codec for the encoding format found in the second file.
The process of taking an analog audio or video wave and turning it into a stream of binary data (i.e. 1's and 0's). Encoding is done by measuring the wave periodically and storing each measurement as a binary value, a process known as sampling. The more frequent the measurements, the better the stored values will represent the original waveform, but this also results in more data to store and transfer. To reduce the amount of data without losing an equal amount of quality, codecs are used to algorithmically analyze and intelligently compress the raw binary data.
The output of the algorithm used by a codec to compress a video or audio stream. A computer must have an appropriate codec installed to be able to create or playback an encoded stream. The encoding format is specific to each stream and cannot be determined just by looking at the name of a file. Instead, a media file must be examined using a player or preview tool capable of understanding that particular container format in order to determine which codec was used on each stream in the file. Some examples of common encoding formats are H.264, WMV, Sorenson AVC, RealVideo, and DivX.
A specialized, often proprietary codec used by many video editing suites to encode video and audio streams while a user is working on editing the content into a final product. Intermediate codecs are usually not recognized by most mainstream video players and transcoders, and must be avoided when exporting your final video or audio project. An example of an intermediate codec is the Apple ProRes codec used by Final Cut Pro.
Measuring an analog audio or video wave periodically and storing each measurement as a binary value. See encoding for more information.
A sequence of data that represents analog audio or video content. A stream usually holds audio or video, but not both at the same time.
To send only the portion of a stored video file that the viewer currently wants to see, rather than the viewer having to download an entire video file before being able to view it. Streaming allows a viewer to quickly watch a small portion of a very large recording, and even jump around in that recording with minimal delays. Streaming is also very useful for broadcasting live events, where the source is a live video camera instead of a stored video file.
Streaming can be used to help reduce unauthorized copying of video content, as it is more difficult (though not impossible) for a viewer to obtain a complete and usable copy of a streamed video file.
To convert the encoding format and/or container format of a media file, usually from a more proprietary format to a more universal format.
Produced by the MPEG working group, this is the standard audio format for use in MP4 files in conjunction with H.264 video content.
This compression standard provides very high sound quality at relatively low bit rates.
Produced by the DivX, Inc. company, this container format is commonly used by programs that can rip (i.e. extract and copy) content from a DVD disc. It usually has a H.264 or MPEG-4 video stream.
Produced by the MPEG working group, this is currently one of the most common encoding formats, making it a good choice for universal compatibility. However, it is covered by various patents that limit the ability to create software or hardware that can read or generate H.264 streams without permission and/or royalty payments to the MPEG-LA licensing group.
A container format developed by Macromedia for their Flash embeddable web player (now known as Adobe Flash). FLV files traditionally contained Sorenson or VP6 encoded video, but today can contain H.264 video.
MP4 files most commonly carry H.264 video streams with AAC audio streams.
Moving Pictures Experts Group – 2. A very popular encoding format for both standard definition and even high definition. MPEG-2 is the standard for DVDs, and is used extensively by digital television for distribution over broadcast, cable and satellite services. Although not used as much as H.264 and VC-1 because MPEG-2 is not as efficient, it is one of the three standards mandated for Blu-ray.
A free and open container format designed to support video and audio streams encoded in several free and open encoding formats, including Theora for video streams and Vorbis for audio streams.
A proprietary codec created by Real Networks that is primarily compatible only with their own player product, though the format can be converted to other more universal encoding standards.
A proprietary codec used primarily in early QuickTime (MOV) video container files from before the mid-2000s.
A free open container format developed by Google and designed to use VP8 video encoding and Vorbis audio encoding. VP8 was purported by Google to be free and open, but there are currently claims by Nokia and other groups that aspects of VP8 are covered by existing patents.
A proprietary video format and file container type created by Microsoft for use primarily on Windows computers. WMV files may be subject to Digital Rights Management controls, which usually render the files unplayable on any media player except for specific Microsoft authored players (e.g. Windows Media Player). DRM controlled WMV files cannot be transcoded by the OIT Media Management system.
A high definition video format with 1080 vertical lines of interlaced (the “i” in 1080i) video, where 540 odd numbered lines are scanned during the first field of video in 1/60th of a second, and the other 540 even lines scanned in the second field. Together, these two fields form a complete frame of video in 1/30th of a second. The resulting image is presented in a 16:9 aspect ratio at 1920 x 1080 resolution. 1080i is used by several television broadcast and cable networks to deliver high definition video.
A high definition video format with 1080 vertical lines of progressive (the “p” in 1080p) video, where all 1080 lines are scanned at once per video frame in 1/30th of a second. Movies for Blu-ray are often scanned and played back at 24 frames per second, as that is the standard for motion picture film cameras. Progressive scanning allows for clearer, shaper images and improves how motion is displayed. The resulting image is presented in a 16:9 aspect ratio at 1920 x 1080 resolution.
Standard definition format with 480 vertical lines of interlaced (the “i” in 480i) video, where 240 odd number lines are scanned during the first field of video in 1/60th of a second, and the other 240 even numbered lines are scanned in the second field. There are two fields per video frame displayed in 1/30th of a second. Used for DVDs, with a resolution of 720 x 480.
Standard definition video where 480 vertical lines of progressive (the “p” in 480p) are scanned at one time to compose a video frame in 1/30th of a second. Progressive scanning allows for clearer, shaper images and improves how motion is displayed. 480p is used extensively in DVD authoring, and is one reason why the resulting 720 x 480 resolution image can be “up-scaled” with high quality on a display designed for 1920 x 1080.
A high definition video format which scans the 720 vertical lines at one time during a video frame in 1/30th of a second. Progressive (the “p” in 720p) scanning allows for clearer, shaper images and improves how motion is displayed. 720p is presented in a 16:9 aspect ratio at 1280 x 720 resolution. Progressive scanning also allows for better “up-scaling” of a 1280 x 720 image to fill a display screen designed for 1920 x 1080. 720p is used by several broadcast and cable networks to deliver high definition video.
A media container format used for many mobile phones.
Advanced Video Coding High Definition. A format using MPEG-4 AVC/H.264 compression originally made for consumer HD camcorders. AVCHD can be played on media players in computers, or burned onto DVD recordable media and played back on Blu-ray machines at 1920 x 1080 resolution.
Developed by Microsoft for use in their Windows PC architecture, the formal name for the AVI is Audio Video Interleave (Interleave because the video and audio are bound together in chunks). AVI is not a CODEC itself. It is a container or a “wrapper” which allows different CODECs to be placed inside for playback. Click here to read more about the history of AVI and AVI players.
The speed and amount of data that can be transferred in a given period of time. Higher bit rates mean higher quality media can be streamed or played back. Overall bandwidth depends upon the processing speed of your computer, along with the network or Internet connection.
Is a number of bits per second that can be transported or processed. Audio and highly compressed video runs in the Kilobits per second range. Other video compressed through different codecs may play at Megabits per second rates, usually because they are playing back higher quality content. Newer codecs, such as H.264, are more sophisticated and very efficient. They can operate at lower bits rates, but still deliver excellent quality video and audio.
An amount of memory set aside to help improve media playback performance by allocating space to either RAM or hard disk drive.
Constant Bit Rate. A recording preference where, regardless of its quality or complexity, the content will be recorded at the same bit rate from beginning to end. The opposite of Variable Bit Rate (VBR), where the bit rate changes up and down according to the amount of data required by the compression algorithm.
CD
Compact Disc. A media format used to store and playback music and data. Typical capacity of 700 Megabytes (MB.)CLIP
A term usually in reference to a section of or sometimes even an entire video program.Similar to a CD in physical structure, but can hold seven times the data capacity. Primarily designed for recording movies in the MPEG-2 format and Dolby Digital Surround sound. DVD-R/RW media can record video or data.
A general term that is often used interchangeably to mean the container format or (incorrectly) a codec itself. Common formats include: AVI, MP4, WMV, 3GP, QuickTime, SWF, MPEG, M4V, RM, DVD, DVR-MS, MKV and FLV.
Ability of video player software to take advantage of the Graphics Processing Unit hardware in a computer, mobile device or game machine to make the decoding and display of digital video faster and more reliable
Location where your collection of audio and video media clips are stored. Can be customized according to how you want to categorize content, and used as part of the interface to provide access to other features.
A type of encoding that, although compression techniques are used, the resulting product can be played back without loss of data.
Encoding that permanently removes data during compression in a way that not only makes the final product much smaller, but still offers very high quality.
A digital audio encoding format, predominant in portable audio devices.
Moving Pictures Experts Group – 2. A very popular encoding format for both standard definition and even high definition. MPEG-2 is the standard for DVDs, and is used extensively by digital television for distribution over broadcast, cable and satellite services. Although not used as much as H.264 and VC-1 because MPEG-2 is not as efficient, it is one of the three standards mandated for Blu-ray.
For digital video, measured by the resolvable detail given the number of the vertical and horizontal pixels on a display device. Other factors such as spatial (still images), temporal (moving images or objects) and the perceived resolution of the viewer makes this more than a numbers game.
Continuous transmission of content that can’t be paused or rewound. Essentially like a live broadcast.
Used interchangeably with encode and conversion. Typically changing one media format to another. Usually involves compression to make the final product into a smaller delivery package.
Variable Bit Rate. An economical way to compress and encode video source material based on the algorithms’ ability to detect changes in the amount of data most appropriate for a particular scene. For video, this saves space by using fewer bits for simple content, and more for complex material that contains lots of changing detail or motion.
A video compression format originally developed by Microsoft for the now defunct HD DVD standard, which was dropped in favor of Blu-ray. VC-1 is one of the three mandated formats for use on Blu-ray. It is an efficient codec, which can deliver very high quality.
