Video formats

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Video is in many cases the source for motion capture, e.g. computer vision, and we typically want to store video together with mocap data. Thus it is relevant to discuss various types of video formats and how they can be used in conjunction with mocap data.

Matroska

Matroska is based on EBML (binary xml, BSD licensed parser: LibEBML2). The matroska container is actually pushed forward by Google as part of its WebM project for an open video codec for HTML5. The WebM codec aims to be as good as H264 but without the licensing issues (open as open source and free as beer). If the WebM projects gains a lot of traction, it could be interesting to use their matroska storage with EBML extensions for our needs.

Some information on EBML (+matroska):

  • supports any kind of binary data
  • they have the notion of Tracks, CueTime (timecode in ns), etc
  • nested data
  • extensible
  • it's use could become very broad (partners: Google TV, Adobe Flash, Intel, etc)

Matroska extensions (via doom9):

  • .mkv: generally video files (with or without audio)
  • .mka: audio only files, can contain any supported audio format, such as MP2, MP3, Vorbis, AAC, AC3, DTS...
  • .mks: a so called "elementary" matroska stream, containing any subtitles stream

MPEG-4 (H.264

Ogg

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