On Thu, Apr 06, 2006 at 04:54:55PM -0700, Steven M. Schultz wrote: > > On Fri, 7 Apr 2006, Nicolas wrote: > > > Huh? It's written in the manpage of mplex: > > -V|--vbr > > Set variable bit rate multiplexing. This is needed to multiplex > > variable bit-rate video streams correctly. > > Right - but '-f 8' implies VBR ;) > > > I don't apply any filter. I spent 2 evenings trying to find good > > Ok - that's the cause (at least indirectly) of the problems. The > encoder's spending too many bits on preserving noise :( > > > settings to denoise the video without any success. Each time the result > > was blur. There was far less details on the pictures... > > > There's a lot of camera shake, and the video comes from an analog > > I know that will drive up the bitrate. > > > camcorder. It's noisy indeed, and some scenes are shot in a forrest (lot > > of details in the background). The edges are blacken using yuvscaler. > > Ah, good - the junk in the edges (especially the bottom) will waste > a lot of bits. 'y4mshift -b' can also be used to blacken the borders. > y4mshift can also center (using -n and -N) the image within the frame > (useful if the black borders are much larger on one side than the > other side). > > > In fact, I'm archiving old Hi8 cassettes shot around 10 years ago. > > Using a MJPEG (is this the DC30+ that's been mentioned or have I > confused this thread with a different one) card? > > > > There's something about the source that's creating files that > > > are right on the edge of being usable. > > > > You probably guess right... The video is really noisy. But I really did > > not find any correct solution to remove the noise without softening very > > much the video. The last thing I tried was that : > > Several things that might help: > > 1. A mild lowpass filter. Yes, y4mspatialfilter can soften the image > if the parameters are too low but a MILD application of a spatial > filter can reduce the noise without losing too much detail > > y4mspatialfilter -L 5,0.92,5,0.92 > > will only reduce the luma bandwidth 8% - could remove a lot some > noise but not a lot of detail. > > 2. Filter only the chroma. Chroma coming from old analog tapes is > quite dirty from what I've seen can be aggressively filtered. > > > 0 -I ACTIVE_702x560+8+8 -M BICUBIC | yuvdenoise -s 2,6,6 -g 0,0,0 -t > > 4,5,5 | /usr/bin/yuvmedianfilter -t 0 | /usr/bin/y4munsharp -L 1.0,0.2,0 > > One thing that you will notice, if you do upgrade to the cvs version > is that 'yuvdenoise' no longer has the -s and -g options. Those > options offered a lot of flexibility that I miss now. > > While you still have the old yuvdenoise you might try the milder > settings of "-s 1,2,2 -g 0,0,0 -t 2,4,4". That should lose almost > no detail but still remove a lot of the noise. > > 3. heavy center pixel weighting median filter. Maybe something like > "yuvmedianfilter -f -R 1 -r 1 -w 16" will be effective. > > But I would avoid 'y4munsharp' if the source is noisy. > > y4munsharp sharpens the NOISE which makes it look even worse and raises > the bitrate needed even more :( > > 4. y4mdenoise is slow but effective. Have you tried that filter? > > > > Maybe adding -E to the encoding parameters will help lower the peak rate. > > > > > > > I fear that could reduce the video quality. It really need to be > > Ah, so you haven't tried it ;) It's not a "filter" in the same > way as you might be thinking ("yuvdenoise"). > > There are some items that the eye can not see but the encoder will > spend a lot of bits on because they're very hard to encode. -E > can help the encoder save bits in certain cases (it's not a constant > "filter" like yuvdenoise!). > > I think a new slogan is needed: "invisible quality is wasted bits" :) > > But if you're that serious about having these precious videos being > playable 20 years from now I'm surprised you haven't invested in > some higher-end capture equipment and software... ;) There are some > fantastic plugins available for FinalCutPro that could be quite useful. > > The other thing I 've noticed when processing (old) analog tapes is > that they deteriorate over time - almost every single one I've looked at > (with the software scopes) has had a color cast problem. Color > correction and black level adjustment can do wonders for a video (a > slight lowering of the black level, also known as "crushing the > blacks", can improve the perceived contrast and richness of the > video). Then too desaturating the lows (dark) can improve the > appearance and lower the bitrate (slightly). > > Good Luck with your latest encoding run. > > Cheers, > Steven Schultz
Steven, I'm now running some tests with the filters on, and the parameters you suggested. The result is nice. I mean, the video isn't very blurry, and the noise is reduced. You asked me why I don't use FinalCutPro? Well, probably because Open-Source is my philosophy. I don't want to use Windows or Mac. As regards to the color correction, I know I can modify the histogram of the pictures in Cinelerra. However, do you know of any automated method of doing the correction you talk about? A command I could include in the mjpegtools pipe for example. ;-) Sometimes in the past, I made an error with color correction. I corrected the histogram of one video, and the only thing I used as the reference was what was displayed on my monitor. Unfortunately, the video looked really different when displayed on a TV. I then discovered the way the luminance is displayed on a monitor and a TV is really different... :-/ Nicolas. ------------------------------------------------------- This SF.Net email is sponsored by xPML, a groundbreaking scripting language that extends applications into web and mobile media. Attend the live webcast and join the prime developer group breaking into this new coding territory! http://sel.as-us.falkag.net/sel?cmd=lnk&kid=110944&bid=241720&dat=121642 _______________________________________________ Mjpeg-users mailing list Mjpeg-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mjpeg-users