[pvrusb2] NSLU2 + PVRUSB2 = Bird-Box Cam

Michael Roitzsch mroi at users.sourceforge.net
Mon Feb 6 15:00:22 CST 2006


>> Is there a computationally-easy way to convert an MPEG frame into  
>> a JPEG - they both use DCTs, don't they?
> As for converting mpeg frame(s) into jpeg, I really have no idea.

It would be possible to do compressed domain transcoding from MPEG to  
JPEG for the I-frames (intracoded frames) only. I most MPEG streams,  
an I-frame appears around every 15 frames. For the other frames (P-  
and B-frames), this is completely impossible, since these are not  
stored as complete frames, but as motion vectors and difference  
information towards an earlier decoded reference frame. You have to  
decode them to reconstruct the actual picture.


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