RatDVD

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ratDVD is a is a highly compressed file type, containing all the contents of a DVD-Video movie, the format is closed source and proprietary. It is currently available only for the Microsoft Windows operating-system. The ratDVD program (transcoder and GUI) works by compressing a full DVD-Video into a .ratDVD file and then playing its contents by on-the-fly decompressing the container and using a DirectShow-compatible DVD-Video player. The .ratdvd movie files compressed by ratDVD are usually one to two GigaByte in size.

ratDVD was only a preview version of the now commercially sold fluxDVD, also closed source and proprietary. While ratDVD contained the features that allowed the home user to create their own archived DVDs, this function has been removed from fluxDVD, allowing only content owners to make and sell fluxDVD archives, (unlike ratDVD, fluxDVD uses a video codec based on H.264).

Video codec

The ratDVD authors claims that the closed source and proprietary ratDVD video codec (called "XEB") does not use ISO MPEG-4 nor H.264 patented technology but does contains routines which is similar in function and even to a small extend in output to what you'll find out there.

From the ratDVD FAQ about the XEB video codec:

  • It is block based (No wavelets anywhere)
  • It has a dynamic GOP structure, P frames have only one reference frame, B frames two.
  • GOPs are significantly longer than normal DVD GOPs and always closed
  • To avoid drift in long GOPs it has a build-in intra-refresh mechanism
  • It has intra prediction significantly more advanced than MPEG2, but not quite as flexible as H.264
  • It uses an integer transformation that approximates DCT
  • It uses a piecewise linear adaptive quant. The Quant level is determined for each macroblock by a simple psycho visual model
  • It has a primitive in-loop deblocking filter
  • Mode decision is part lagrangian optimization, part ad hoc based on statistics manually tuned to fit.
  • It uses an in-codec scaler and the actual encoded picture size can vary in both dimensions between GOPs
  • In order to maintain navigation ability and the reconvertability the codec suffers some limitations that others don't
  • The MUX format is H.262 + some private extensions


Audio Codec

The ratDVD authors claims that the closed source and proprietary ratDVD audio codec (refered to as "AC-3 VS" or "Dolby Virtual Surround AC-3") is AC-3 based but only used two (stereo) channels and achives virtual surround sound similar to Dolby Pro-Logic: "Dolby Virtual Surround AC-3 uses the way your ears works to generate a surround feeling from a 2-channel signal. By using Virtual Surround you're able to drop the AC3 bitrate from 384 Kbit/s down to 192kbit/s, while maintaining the surround feeling and superior quality. The best audio is uncompressed LPCM which is rare on DVD's and consumes massive bitrate - especially in a surround configuration (I've never seen a surround LPCM DVD although it's within the spec to make one). Second best is the DTS format. Unfortunately DTS is very expensive in bitrate and isn't supported by all devices. Insignificantly worse than DTS is 5.1 AC3 which is typically 384 Kbit/s. Obviously 384 kbit/s is around 170 megabyte per hour of movie per audio track which may still be too much. For this situation AC3 VS is a great solution as it gives decent surround performance but at half the bitrate. Other Audio formats like MP3, Ogg-vorbis and so forth, have the significant disadvantage that they're not supported by stand alone DVD players which would mean a second conversion step would be required with a second step of generation loss. Also they are not designed for surround. Therefore if bitrate is an issue AC-3 Virtual Surround is an ideal solution".

Container

ratDVD uses a ZIP based container format, containing all the contents of a DVD movie. The .ratDVD files are usually one to two gigabytes in size. The actual video files uses a XVO extention.

> unzip -l example.ratDVD 

   Length     Date   Time    Name
  --------    ----   ----    ----
        94  09-23-05 13:59   Version.xml
      4497  09-24-05 01:12   AV_TS\StreamData.xml
     10240  09-24-05 01:12   AV_TS\VIDEO_TS.IFO
    106496  09-24-05 01:12   AV_TS\VTS_01_0.IFO
     14336  09-24-05 01:12   AV_TS\VTS_02_0.IFO
     14336  09-24-05 01:12   AV_TS\VTS_03_0.IFO
     14336  09-24-05 01:12   AV_TS\VTS_04_0.IFO
       243  09-23-05 14:07   AV_TS\VTS_01_0.VSI
     16723  09-24-05 00:59   AV_TS\VTS_01_1.VSI
       159  09-24-05 01:04   AV_TS\VTS_02_1.VSI
        63  09-24-05 01:05   AV_TS\VTS_03_1.VSI
       191  09-24-05 01:12   AV_TS\VTS_04_1.VSI
  11692032  09-23-05 14:07   AV_TS\VTS_01_0.XVO
1073739776  09-23-05 14:17   AV_TS\VTS_01_1.XVO
 321810432  09-23-05 23:06   AV_TS\VTS_01_2.XVO
   9205760  09-24-05 01:04   AV_TS\VTS_02_1.XVO
   1929216  09-24-05 01:05   AV_TS\VTS_03_1.XVO
  13617152  09-24-05 01:12   AV_TS\VTS_04_1.XVO


See also

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