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Wiki > Main > PluginVideo (compare)

Difference: PluginVideo (r5 vs. r4)

Video

A video player in grayscale, with sound. NOTE: This plugin only works on the Archos Recorders and Ondio.

This plugin acts as a ViewerPlugin for .rvf files. RVF is a special video format needed for video playback on the archos; if you want to watch videos you need to convert them into that format. There are 2 methods to do this, either using a set of command line utilities, described in the VideoTutorial and available for both Windows and Linux, or a DirectShow filter in conjunction with an easy to use GUI application (Windows only).

Keys

RecorderOndioFunction
Off OnOff Quit Plugin
Play Mode Stop seeking / pause / restart
Up/Down Up/Down Increase / decrease volume
Left/Right Left/Right Start seeking backward / forward
F3/F2 Mode+Up/Mode+Down Increase / decrease contrast

Miscellaneous

For the technically interested user:

The archos lcd screen is only able to display black & white. The video player simulates grayscales by quickly flipping the pixels between black and white. The ratio of black and white pixels displayed at a pixel spot defines the perceived brightness of that spot. There are some implications of this technique:

  • Since it requires changing the display content very fast, some optimization had to be done to the lcd driver. Even with today's highly optimized lcd driver, a fair amount of cpu power is used for this pixel flipping alone.
  • The flipping frequency has to be synchronized to the internal scan frequency of the lcd, in order to avoid excessive flicker and artifacts. Unfortunately, exact synchronization is not possible because of 2 reasons: (1) The internal scan frequency is not constant, since it is generated by a simple RC oscillator. It is temperature dependent. (2) There is no feedback information available from the display.
  • Since exact synchronization is not possible, some artifacts ("fishes") are sometimes visible. This can't be avoided.

The same method was used later to develop the grayscale library and its new, way faster incarnation, the greyscale library, which is currently used by the JPEG viewer, the mandelbrot set explorer, the cube demo, the plasma demo and the grayscale library demo?fire demo.

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CategoryPlugin: Video viewer, in grayscale, with sound! [RecorderDONE, OndioDONE]

r5 - 09 Apr 2008 - 18:33:28 - JensArnold

Revision r5 - 09 Apr 2008 - 18:33 - JensArnold
Revision r4 - 21 Nov 2007 - 13:13 - DaveChapman
Copyright by the contributing authors.