Dear Mark and Stefan, many thanks for your investigations. I'll do what you suggest and let you know as soon as possible.
At present I can only say that: 1) the distance between the source and the card doesn't seem to matter, because the same results are obtained when I try to record from the S-Video output of my brand new digital camcorder (the cable is about one meter long). 2) the electrical appliances near the PC have always been the same for a very long time before the problem appeared. Anyway I will try to turn off everything. For the recording bitrate, I can only change decimation and JPEG quality, because I use lavrec. The image you have seen is a frame extracted from an AVI file produced by lavrec. If I understand MJPEG, that image is exactly the JPEG image created by the Zoran chipset, without any changes. Could it be of any help in the investigation trying to record at decimation 2? I usually record at full frame (decimation 1) and 40% JPEG quality. More than that gives me lost frames. Maybe 50% JPEG quality is possible, but I never tried. Best regards. Mark Heath wrote: > I've split this image into it's Y-U-V channels, > > There appears to be no noise in the chroma channels only the Luma > channel. > > This could be due to: > > * the chroma channels being half resolution, not enough resolution to > represent the noise pattern. (below the nyquist value) > * the interference frequency is not high enough to cause colour shifts. > > Or due to JPEG compression. > > * notice that the noise falls cleanly within Macroblock boundaries. > * the noise may be falling below the quantizable threshold in those > areas. Thus not being encoded into the Macroblock. > > If you get to capture the image again, maybe do it at a very high > bitrate, so we don't see compression artifacts. > > I have seen this type of noise before, even recorded onto a digibeta > provided by Universal, but never looked into methods of removing it. > > Have you tried a bit of trial and error, to see if the noise goes away? > > * Turn off all electrical appliances. > > * Try the capture source closer to the computer. > > Mark > > -- > Check out my latest YUV tools at http://silicontrip.net/~mark/lavtools/ > > On 08/03/2008, at 8:34 AM, Andrea Giuliano wrote: > >> Okay, you and Burkhard suspect radio interference. But you have not >> seen >> the full pictures I sent to Bernhard Praschinger. In those picture you >> could see that the pattern is not spread all over the frame: the >> trunks >> of the trees, and the rocks too, are only affected very little, if >> even >> not at all. Could an interference affect some colors and not other? >> I'm >> not expert of interference, nor of colors, indeed? >> >> So here is a link to one of those frames: >> >> http://www.webalice.it/sarkiaponius/00000669.jpg >> >> It's just 54K big. If you zoom around the trunks or the rocks you will >> surely understand what I'm trying to say (sorry, my native language is >> neapolitan, not english...) > > > ------------------------------------------------------------------------- > This SF.net email is sponsored by: Microsoft > Defy all challenges. Microsoft(R) Visual Studio 2008. > http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ > _______________________________________________ > Mjpeg-users mailing list > Mjpeg-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/mjpeg-users -- Andrea ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users
