Now paying attention to licensing policy I've found great ffmpeg library (which is used in many-many projects on different OS). And ffmpeg is fortunately LGPLed. So as GledPlay is.
A've chosen Mpeg4 decoder from it, because it is frame based, so it will be more easy to skip frames.
Now I'm at the stage of having ability to decode frames to file, so the light in tunnel is very close
But, have licensing question, because I'm not very competent in this field.
To somehow ease my work in porting I've used ported version from TCPMP's ffmpeg plugin. All FFMPEG files in this source at the top has all LGPL license type. And all native TCPMP files with GNU license was removed.
I think as I removed GNUed files from this project I can make this ported library LGPLed?