I had the same problem. "Illegal instruction" means the program tries to do operations that are not supported by the processor. The most ffmpeg binaries are compiled for todays desktop processors. So you have to compile your own ffmpeg binary. Also you have to carefully choose the ./configure flags to meet the hardware criteria of the Quark processor (for the start: --disable-asm is required and make sure it is compiled for a 32 bit-system). I was able to get a ffmpeg binary that was able to start correctly, even to get some file format transformations done. But I never spend enough time to find the correct ./configure settings to get a working video capture.
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