On Sun, Mar 20, 2005 at 04:20:48PM -0800, Steven M. Schultz wrote: > > On the recently discussed topics of "blocks in dark scenes" and > "does the encoder see things differently than the eye" I have > something that might be of interest. > > I pulled up a still frame from a DV file that to the eye looks > black. The encoder on the other hand will see quite a bit of R G B > (more than I expected) that needs to be encoded.
What you are likely seeing there is the limits of the accuracy of the ADC of whatever encoded the video. I.e., ADC noise, which will always be present in varying amounts. Part of what likely makes pro level gear so expensive is the amount of design work that goes into building a relatively noise free ADC for the digitization pass. Consumer level gear isn't going to have the same accuracy ADC built into it. > After applying the 'desaturate lows' (along with other color > correction) the RGB levels are about 1/5 as high without visibly > affecting the overall picture. The result is that the encoder > produces much better looking dark areas. What about having a "selective median" (for want of a better term) type filter. What I'm thinking is a median type filter that becomes more aggressive as the overall luminance of the frame / block becomes darker. Is there any way to perform something like that with any of the existing filters? And would doing something like that provide a useful filtering result? > Color correction's a subject for another mail item ;) It's amazing > how grungy some tapes are and how much better the video looks after > a little nudging of the whitebalance, black level, contrast and so > on. Well, if the source "tape" is VHS, then the system has taken an already decimated NTSC color signal and further decimated (ruined?) it before recording it onto the tape. ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
