Digital Digest
Digital Digest :
Home
| DivX Digest
| DVD Digest
| DVDR Digest
| Forum
  Contact
| Links
| Search
Home
| Articles
| Logos
| Movies
| Software
| Help
 



What's Here

DivX MPEG-4

  • Home


  • Articles
  • Logos
  • Movies
  • Software
  • Subtitles


  • What is DivX ?
         • Glossary


  • Forum
  • Links


  • Digital Digest


    Home - DivX Help ?

    Glossary DivX Digest


    This page contains a list of the most common jargons and technobabble that you may encounter in the world of DivX and digital video. By no means is this a complete list, and overtime, more will be added.


    Glossary Contents



    ACM
    ACM stands for Audio Compression Manager. ACM codecs are audio codecs that will work in such tools as FlasKMPEG or VirtualDub (eg. the Radium MP3 codec, based on the Fraunhofer ACM codec, or the Ogg Vorbis ACM codec).



    ASF
    ASF stands for Advanced Streaming Format. It is a proprietary format developed by Microsoft for video streaming (also available for offline uses). Most ASF files are based on Microsoft's MPEG-4 V2 technology.



    Authentication
    A step needed before CSS encrypted DVDs can be read. Your DVD player will authenticate any DVD that it tries play. Once authenticated, the authentication will stay for the current Windows session. This is why some DVD rippers require you to play back the DVD to be ripped prior to ripping (although most DVD rippers now have built in authentication engines).



    AVI
    AVI stands for Audio Video Interleave. AVI is a file format, like MP3 or JPG. But unlike these formats, AVI is a container format, meaning it can contain video/audio compressed using many different combinations of codecs. So while MP3 and JPG can only contain a certain kind of compression (MPEG Audio Layer 3 and JPEG), AVI can contain many different kinds of compression (eg. DivX video + WMA audio or Indeo video + PCM audio), as long as a codec is available for encoding/decoding. AVI all look the same on the "outside", but on the "inside", they may be completely different. Almost all tools on this site are not just DivX tools, but also AVI tools, so will probably work with other codecs.

    There is no such thing as a "normal" AVI file, but the closest you can get is probably an AVI file that contains no compression. AVI files has been around since the time of Windows 3.1, so by no means is it a new thing, and is probably the most common video format around (although its popularity wavered a few years ago, but has since come back with a vengeance due to the emergence of DivX).

    AVI files may also have limits under Windows 95/98, and for more information, please read this article. Note that AVI files without file limits (other than the Windows Fat32 file limit) are usually referred to as OpenDML AVI files.



    BIT
    BIT stands for Binary digIT. Basically, a BIT is either 0 or 1.



    BITRate
    See Data Rate.



    Byte
    A byte is simply 8 BITs.



    Codec
    Codec stands for COder/DECoder. It is a small piece of software that allows you to make/play movie/audio compressed in a certain format. MPEG-1, MPEG-2, MPEG-4, DivX ... are all codecs. AVI, ASF, WMV are not codecs, but file formats. AVI is also a container format (see below for more information), meaning it can be made using many different codecs.



    Compression
    Compression uses mathematic algorithms to store large amounts of digital data in a relatively small amount of space. There are two main kinds of compression, lossy, and loss-less. Loss-less compression includes the RAR/ZIP format, where the original data is compressed, and when de-compressed, the data has not changed. Lossy compression includes most video compression formats, such as JPEG, MPEG-1/2/4 - this means that when the digital data is compresssed and de-compressed, it is no longer the same as the original (usually denoting a loss of quality).



    CSS
    CSS stands for Content Scrambling System. It was designed to ensure that DVDs cannot be copied digitally. CSS is a relatively weak encryption scheme that has since been cracked left, right and center. See DVD Rippers



    Data Rate
    Also known as BITRate. It is the amount of data in a particular space of time (eg. a second) - it is a property for both digital video and audio. If a video is said to have a constant data rate or constant BITRate of 150 bytes per second, it means that in every second of video, 150 bytes is used to store the video. BITRate can be constant (CBR) or variable (VBR). CBR means that the stated BITRate will be constant throughout the video, while VBR will mean that the parts of the video that needs more BITRate will get it, while parts that don't need it will have a lower BITRate.



    De-Multiplexing
    Opposite of Multiplexing. It refers to the separation of an audio and video stream. For example, DVD VOB files are basically multiplexed MPEG-2 video with either AC3, MPEG, DTS, or Linear PCM audio. De-multiplexing a VOB file will mean splitting the MPEG-2 video from the audio.



    DeMux
    Short for De-Multiplexing.



    Descrambling
    Usually refers to Descrambling CSS encrypted/scambled files. See CSS and DVD Ripping.



    Data Rate
    Also known as BITRate. It is the amount of data in a particular space of time (eg. a second) - it is a property for both digital video and audio. If a video is said to have a constant data rate or constant BITRate of 150 bytes per second, it means that in every second of video, 150 bytes is used to store the video. BITRate can be constant (CBR) or variable (VBR). CBR means that the stated BITRate will be constant throughout the video, while VBR will mean that the parts of the video that needs more BITRate will get it, while parts that don't need it will have a lower BITRate.



    DivX
    The DivX codec is based on MPEG-4 video compression standard, designed primarily for video transfer over low to mid bandwidth networks (eg. Internet, WAP ...).

    There are in fact 2 major codecs, both name the "DivX codec". But the newer one, which used to be part of the open-sourced project at Project Mayo (now under a licensing scheme), is more commongly referred to as "DivX For Windows/Linux/Mac ...", whereas the orginal codec is sometimes referred to as the "DivX ;-) Codec". The version number of these 2 major codecs are also different - the original being 3.xx, while the new ProjectMayo codec has a version number of 4.xx.

    Most older/existing movies are encoded with "DivX ;-) Codec", since the new ProjectMayo DivX codec is still being developed.

    The original DivX 3.xx codec is based on Microsoft's MPEG-4 V3 codec (ASF was based on MPEG-4 V2). The reason why the codec was "hacked" and re-distributed is because Microsoft's codec did not allow one to encode to AVI (they only wanted people to encode to ASF/WMV), which is far from being convenient. The DivX 3.xx codec also includes hacked versions of a MP3 codec and a WMA codec. The AnglePotion, MPEG-4 and SMR codecs are all in the same boat. There is also a VKI (Scene Detect) patch that will insert keyframes at scene changes for you automatically, which will improve picture quality.

    The new DivX 4.x codec has nothing to do with Microsoft - it has been developed entirely from scratch, and is still under development (hence less then perfect compatibility/efficiency/quality). In time, the DivX 4.xx codec will completely replace the 3.xx codec, but for now, the 3.xx codec offers better compatibility/efficiency/quality. The 4.xx codec is not compatible with the 3.xx codec, and vice versa.



    DIVX
    DIVX has nothing to do with DivX (AVI/MPEG-4). DIVX refers to the failed digital video rental system. This new DivX is differentiated by it's capitalisation (i and v are small case) and usually written as DivX ;-) or DivX MPEG-4. DIVX was a pay-per-view DVD rental system, which basically meant that you paid around $US 4.50 per movie (the disc has no extra features on it, and may not even be widescreen, let alone anamporphic) and you get 48 hours of viewing time. After you have used up viewing time, you'll need to pay an extra $US 2.50 to open a new viewing period. DIVX was to become a competing force to DVD (although theoretically, this shouldn't be the case), and many studios might have preferred to release movies only on DIVX, not on DVD. DIVX is now dead, thankfully, because of the negative support it got from the DVD community.



    DVD Conversion
    DVD Conversion refers to the process of converting DVD's MPEG-2 video and digital audio to another format, usually a lower quality one, in order to be able to store the movie on a CD media (or on your hard-drive), rather than on DVD. For more information on DVD conversion, please refer to DVD Digest's DVD Conversion Guide.



    DVD Ripping
    DVD ripping is not the same as DVD conversion. As you may know, DVDs are encrypted by CSS, which scrambles the DVD file as it is copied. DVD ripping refers to copying the DVD to your hard-drive without the scrambling effect. The term "Ripping" comes from the extensive used of the term "CD Ripping", which means copying the audio from the CD digitally (bit for bit), as opposed to converting it to analog, and then let your sound card convert it back. Perhaps DVD Decryption is a better term to describe this process. For more information, please refer to RipHelp's DVD Ripping Guide.



    Encoding
    Refers to doing something to a video into a particular format (as in "encoding a video into a particular format). Usually refers to compressing to a particular compression format (as in "encoding video to DivX"). Decoding is the opposite of encoding.



    Frame
    Movies are basically moving pictures - a series of pictures, each displayed for only a fraction of a second, fast enough so that the human eye won't be able to see each individual frame, but rather, a movie. This same techinique is also behind 3D animations/games, which is rendered on a frame by frame basis (eg. in Toy Story 2, each frame took hours to render on a super computer).



    Framerate
    The number of frames in a given space of time (eg. 1 second). Also known as Frames Per Second (FPS). NTSC Film has a framerate of 23.976, NTSC has a framerate of 29.97 and PAL material has a framerate of 25.



    Keyframe
    Please refer to Nicky Page's Keyframes and Delta frames guide for more information.



    IFO/BUP
    IFO files contain the formatting information of the VOB files, which tells the DVD player exactly how the DVD should be played (eg. aspect ratio, subtitles, languages, menus ...). BUP files are backups for IFO files, which are needed if the IFO files gets corrupted. If you rip the DVD without IFO files, then the VOB files may not play correctly, or may not even play at all. Similarly for conversion, IFO files are essential since video converters like FlasKMPEG (which supports IFO parsing) will need them if you want to encode videos, or fix multi-angle ripping problems. Definition curtesy of RipHelp's DVD Ripping Guide.



    IFO Parsing
    IFO parsing refers to reading through the IFO file and extracting the information needed to manipulate the VOB files that the IFO files "control". DVD players are able to parse the IFO file, hence provide things such as menus, subtitles, languages controls - if they simply read the VOB files without parsing the IFO file, then none of these controls would be available. Similarly, some DVD conversion tools also support IFO parsing. Also see IFO/BUP files.



    MiniDVD
    An unofficial format for playing back MPEG-2 files. Please refer to this page for more information.



    MPEG
    MPEG stands for Motion Picture Experts Group. This is the same group that made the MPEG-1 (used in VideoCDs), MPEG-2 (used in DVD and SuperVCDs and other high bandwidth systems) and MPEG-4 (ASF, DivX, WMV, low-mid bandwidth systems) standards. They are also responsible for MP3 (MPEG Audio Layer 3) and AAC audio compression standards.



    Multiplexing
    Opposite of De-Multiplexing. It refers to the joining of an audio and video stream. For example, DVD VOB files are basically multiplexed MPEG-2 video with either AC3, MPEG, DTS, or Linear PCM audio.



    DeMux
    Short for De-Multiplexing.



    Proprietary Format
    The problem with any proprietary format is the format's specifications are closed, and therefore, there aren't as many tools (especially free ones) that will support them. This is why while DivX/AVI tools are plenty, ASF or WMV tools are not as common (except for tools released by Microsoft) - conversion from a closed proprietary format to another format is also limitd, as per the intentions of the people who owns the format.



    PC-DVD
    PC-DVD usually refers to DVDs on computers (eg. DVD-ROM, DVD decoder ...). Please refer to DVD Digest's PC-DVD Guide for more information.



    SBC
    SBC stands for Smart Bitrate Control. A new encoding method, using NanDub, that encodes the movie dynamically and on-the-fly, not based on preset values. This new method will give you better picture quality, as well as a reduced file size. Please refer to Nicky Page's NanDub SBC guide for more information.



    Subpicture
    A subpicture stream found in VOB files normally refers to the subtitles. Subtitles on DVDs are not stored as "text", but rather, as a video stream. A subpicture stream is one that overlays on top of the main picture stream (ie. the movie), and on a DVD, the subpicture stream can be turned on and off.



    Super VideoCD
    Also known as SVCDs or SuperVCDs. Please refer to this page for more information.



    VBR
    VBR stands for Variable BitRate. See Data Rate.



    VideoCD
    Also known as VCDs. Please refer to this page for more information.



    VOB
    VOB stands for Video OBjects. DVD movies are stored in VOB files. Each VOB file has a number of video/audio/subpicture streams. More information on VOB files (eg. naming structure) can be found in RipHelp's DVD Ripping Guide.



    WMA
    WMA stands for Windows Media Audio. It is a proprietary format developed by Microsoft for audio streaming and compression. WMA files, theoretically, has double the compression rate of MP3s, although this is debatable.



    WMV
    WMV stands for Windows Media Video. It is a proprietary format developed by Microsoft for video streaming (also available for offline uses). Most WMV files are based on Microsoft's MS-Video V7/V8 technology, similar to MS-MPEG-4 V3.







































    Copyright Digital Digest 1999 - 2005. Duplication of links or content is strictly prohibited. Read our Privacy Statement