Hello,
I've completed a prototype for an NTSC decoder blockset for gnu radio. It's not
very sophisticated but it lets you see video on the screen using gr-video-sdl.
My development platform is Ubuntu 6.10 x86.
The signal starts out by using a custom AGC which simply scales the samples by
dividing all samples by a local maximum. This puts most of the samples in the 0
to 1.0 range. Then the frame detector uses a simple threshold method to
determine when pulses begin and end. The length of time between pulses is used
to determine the type of pulse. A simple state machine keeps the output
buffered correctly so the screen doesn't get out of whack.
Current features:
* Black/White reception (vertical and horizontal sync)
* Contrast/Brightness adjustment (still a little buggy)
Planned features:
* automatic black level
* color
* stereo audio
* better sync detection
* documentation
Any feedback would be appreciated.
http://www.danielgarcia.info/thesis/
http://www.danielgarcia.info/thesis/files/gr-video-analog.tgz
-Daniel
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