On Wednesday 18 February 2004 20.16, you wrote: > >> I found the problem. It is concerned with lavtools. I was > >> recording the fooprint using lavrec. Apparaently, it produced many > >> pixels (at least 10% per image) with YUV out of the spec > >> (16<=Y<=235, 16<= u,v <= 240). Since matteblend.flt is programmed > >> using the exact spec, a lot of overflow/underflow conditions > >> appeared giving rise to the above mentioned effects. I added some > >> code to matteblend.flt.c in an attempt to force the standard. This > >> worked well, although the process became much slower. > > ... > > >That pixles are a slight problem, because they are nor allowed, but > >appear, because of the transmiton. There should be one or two mail from > >Andrew about that problem. > > Such pixels are not really "out of spec"... all values in the range > [1,254] are legal --- even though they do not map back to R'G'B' > values. (For example, Y' < 16 is "blacker than black".) > > The specification was created this way on purpose, to give some room > for ringing and over/under-shoot in both the signal acquisition and > the digital operations that follow. The pixels should only need to > be clipped to the [16,235]/[16/240] range when converted to R'G'B'... I see. This is the answer to my question. Why is the complete range [0,255] not allowed?
> > ...AND, here, the value of the alpha frame pixels in matteblend.flt > should also be clipped (because they are being implicitly converted > into a [0,1] scale). But, the output pixels (and the other inputs) > should not. > > (The output should be restricted to a [1,254] range, but given the > math involved and legal input pixels, clipping is probably not > necessary.) This is what I did. The luminance channel of the matte is used in a convex combination of the input sources thus using the [16,235]/219 range. Michael > > -matt m. ------------------------------------------------------- SF.Net is sponsored by: Speed Start Your Linux Apps Now. Build and deploy apps & Web services for Linux with a free DVD software kit from IBM. Click Now! http://ads.osdn.com/?ad_id56&alloc_id438&op=click _______________________________________________ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
