Container & Codec:
In digital video technology, your video files will consist of both the picture (video) and the audio (or soundtrack), each in independent components referred to as streams. In order to more conveniently access, store and share these, the video and audio streams are packaged together in a 'container' file. This is essentially the wrapping that keeps them together, but also works to identify the data in the various streams and helps synchronize them together during playback.
The word Codec is the short form of Coder/Decoder (or also compressor-decompressor), which describes the two parts of its job. It is basically a device or computer program that either decompresses (or decodes) your video file so that you can play it back or compresses (or encodes) it into another format for more efficient storage. Some containers can only a few specific codecs whereas others support wider amounts and types.
If you have ever used digital video files on your computer, you know that their often hefty file sizes tend to take up quite a lot of storage space on your hard drive. Digital video compression technology creates a solution to this for those of whose hard drive storage is not infinitely expandable as our video collection grows.
With little or no compromise of the end-product, compression removes non-essential data from the file and more efficiently packs it into the compressed (or encoded) video file, sometimes reducing it to a fraction of the original file size. Depending on your need for quality video and storage efficiency, you can choose different compression settings to decide how much of each to keep or throw away.
High Definition Video:
Describing video as Standard Definition or High Definition refers to the display resolution of the video image. The display resolution is the number of pixels in a single horizontal or vertical line of the image. (Imagine drawing a line of dots really close together in different colors and shades; the more dots in a given space, the more vibrant or clear the final picture will be). The ratios of the amount of pixels in the width to the amount of pixels in the height of an image are referred to as aspect ratio. For example, if the image captured contains 1280 pixels across and 720 pixels up & down, the resolution is written as 1280x720 and its aspect ratio is 16:9. A video with the resolution 640x480 would therefore have an aspect ratio of 4:3.
H.264 & AAC:
The H.264 video codec is the most new-and-improved industry standard for video compression. Also referred to as MPEG-4, part 10 or AVC, it improves upon earlier standards such MPEG-2 and MPEG-4, part 2 ASP (around which the original DivX codec was created). Many formats and platforms have already adopted it thanks to its super efficient compression of high definition video content.
AAC refers to a compression for multichannel audio streams often used in conjunction with H.264 video within the MKV file format. Requiring less bitrate and suffering fewer audible artifacts than MP3 audio compression, AAC audio provides crystal clear theatrical surround sound at a fraction of the resources.
What is MKV?
If you are watching a video, you have both sound and picture; in a digital video file this means that you will have two streams, one for audio (sound) and one for video (picture).
Rather than having two separate files for each part of the video, the two streams are combined in what is called a 'container'. This is similar to using a ZIP file, but digital video containers have added functions that these do not, such as helping keep your sound and picture in sync.
Examples of a digital video container are file extensions such as .DIVX, .AVI, .MPG or .MOV to name just a few. Your video files encoded with the DivX codec can com in either a .DIVX or .AVI container format. The .DIVX container is exclusively for videos encoded with the DivX codec; the .AVI container can hold many different types of video streams, including but not limited to DivX-encoded video.
The .MKV file extension denotes another digital video file container created by Matroska. The .MKV container provides multimedia files with many advanced features for audio/video compression that are currently unavailable in other standard formats such as .AVI. These features optimize even further the high-definition playback of compressed video such as H.264, further improving your video experience. With the playback support of MKV files containing H.264 video and AAC audio streams, DivX PlusTM only further streamlines and simplifies accessibility to these true HD files.
In computing, the minimum storage unit is a bit. The bitrate, or data rate, is a measure of the number of bits processed in a specific measure of time, usually in seconds. For multimedia files, this indicates the amount of data stored for each second of recorded video or audio. This can be either constant or variable, depending on the type of encoding of the file. A file encoded with a higher bitrate, or more bits per second, will lend to a larger file size but a higher video quality than its lower bitrate counterpart.
When compressing multimedia data, a lower bitrate is often chosen. If a video file is compressed substantially to create a smaller size, a common byproduct is the presence of artifacts. Compression artifacts can be seen in the quality of the picture (blockiness, pixelization, or other optical disturbances) or heard in the quality of the sound (ringing, echo, dropped or garbled sounds).