-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Wiebe Cazemier schrieb: > To clarify on the brightness issue a bit. When I have my video driver set to > x11-xv, > the brightness in the composite and view video window, is "unstable". ...
Hi! this is a often reported problem, while the circumstances under which it arises are somewhat complicated and difficult to track down. (I was suffering from it myself at times). Let me explain the situation a bit... When you use the X-xv, you use a different method of outputting video images, which is usually hardware accelerated. This XV-output is showed as an overlay over the normal output produced by your X server. Now, under some circumstances it can happen that both output methods produce a different visual result from the same pixel data. A common situation is when some gamma correction is involved. For example, the X server may be configured to correct for your monitor's gamma, i.e. it modifies the pixel values on the fly. In most cases this means making dark regions brighter (as monitors often have a too steep gamma curve, so that even dark grey pixels (e.g. 15% grey) are already displayed as black. And if the xv output method doesn't apply the same gamma correction (for example it doesn't apply any correction at all), then the visible colours are different. Now comes the part specific to cinelerra: this application reads input data from your source media, decodes it, probably manipulates it and then sends it to output again. But there is a special facility which detects if the image data isn't modified at all, in which case it could use a faster method employing the X-xv display. But the moment the application has to do some modifications to the video frames (e.g. when you move the fader away from 100% or if you use the compositing facilities of cinelerra (the "camera" or "projector") to offset the frame, then it does this manipulations using the CPU and outputs the resulting data differently. The switch-over may even cause a short flicker on some graphic boards. The problem now is: the judgement what is the "right" display depends on your specific circumstances. If you work with image data and do a colour/brightness correction, than this includes inadvertently the display characteristics of your monitor. If you look at your results on another monitor or using another gamma correction, suddenly everything seems to be wrong. That's the reason why professional setups use these expensive colour calibration and correction profiles. hope this helped clarify the situation a bit Greetings Hermann Vosseler -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFIAYltZbZrB6HelLIRAm8XAKCQQ2bdxtPP/CZC7vzI0p97wqamxQCfZisF J2Z1g6im2IfmSVx9qLKVV+0= =yUkf -----END PGP SIGNATURE----- _______________________________________________ Cinelerra mailing list [email protected] https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra
