Re: [Mjpeg-users] Odd artifact from mpeg2enc rc92
Hi Richard, I finally got the y4m from Steven and I now know what's going. Actually, I should have been able to tell you very soon just by looking at the command line but ... that's life. Anyway I've Cc: Bernhard as 'honorary question answerer and Doku whipper-in' in case something like this comes up for others. On Thursday 04 December 2003 04:57, Richard Ellis wrote: > Has anyone noticed mpeg2enc rc92 creating odd "flashing" artifacts on > what should be otherwise generally smooth color backgrounds? I've > attached a small jpeg (29k) showing an example of the artifact. > ... > -f 5 -n n -a 2 -V 230 -B 224 -S 8000 -b 9576 -q 10 -I 1 -G 54 -H -^ > -N 0.0 -X 200 -Q 4.0 -R 0 -d -4 4 -2 4 Beep error spotted. The coloured splotches you are seeing are 'DCT mismatch' artefacts! What is happening is that there are very slight rounding differences between the iDCT and dequantisation routines in the encoder and the decoder. For P frames these differences steadily accumulate in the decoder as each P frame encoding assumes the results of the previous P frame *decoding*. Normally, these: - Simply don't occur (not such a 'heavy' -Q really putting extreme values in, more textured less near-maximum brightness areas) - Are invisible because in sensible-length GOPs a I frame comes along where an image is encoded 'from scratch' with zero accumulated differences - Are invisible because B frames mean far fewer P frames occur between I frames reducing the accumulate difference. However, with your setup you inadvertently created a worst-case scenario for mismatch artefacts: loong GOPs, extreme quantisation matrices, and a very bright slightly noisy (video capture) smooth image area! The real solution is to simply avoid excessively long GOPs. The compression gains beyond the 'normal' GOP lengths are pretty minimal and you can see the potential disadvantages! Andrew PS You may be wondering why MPEG-4 / DivX encoders can use mega-long GOPs. Easy: MPEG-4 rigidly defines the numeric behaviour of DCT/quantisation algorithms. They have to be bit-exact matches to the Spec so the mismatch problem doesn't occur (or at least not to such an extent). PPS The DCT/iDCT routines in mpeg2enc are 'o.k' but not hugely accurate: some nice high-precision SSE based ones are something I'd like to code up but other jobs currently have higher priority. --- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click ___ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
[Mjpeg-users] recording a powerpoint presentation
Hello, I want to record a powerpoint presentation to VCD. I will use OpenOffice to play the presentation. But how do I record the video output to harddisk? Has anybody done this, or something similar, before? I'd prefer a software solution. Maarten --- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click ___ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
Re: [Mjpeg-users] recording a powerpoint presentation
I answer myself: xvidcap > I want to record a powerpoint presentation to VCD. I will use OpenOffice > to play the presentation. But how do I record the video output to > harddisk? Has anybody done this, or something similar, before? I'd prefer > a software solution. --- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click ___ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
Re: [Mjpeg-users] Re: yuvkineco with good capture
Hi. Yes, yuvkineco expects raw captured materials, it is weak against encoded or denoised materials. Both -c and -n regulate pulldown cycle detection sensitivity (-n affects also deinterlacing). Bigger value of -c or -n causes sensitivity lower, but stronger against noises. -C reports noise level, I'd hoped it suits -n, but it was often too big, especially with materials those were not 2-3 pulldown, so I could not write about reported noise level. I recommend -n 10(default) or lower, if reported noise level was lower, lower than it. With movie for theaters, containing little pulldown cycle change, specify -c big. With TV program, film recorded and video edited, containing many pulldown cycle change, specify -c small. If you want to know more about what yuvkineco is doing, set environment variable MJPEG_VERBOSITY=2, yuvkineco will print debug information. --DEBUG: [yuvkineco] 00:00:000:068:254:12 4:12 -47:17 -24391:158 -12:2617855:21 0 10 2333 0 7 - - --DEBUG: [yuvkineco] 00:00:00 68:254:124:12 -47:17 -24391:158 -12:2617855:21 -12:21 0 21 32001322 3 7 5 4 --DEBUG: [yuvkineco] 00:00:03 -999:158-999:2617855:21 -12:21 -27922:770:2997851:17 -25:25 1299 01200322 4 7 - 5 4 : : each fields are: * timecode * field difference:frame difference * 8 * frame offset * frame dropping threshold * flags*8 (frame marked 0 or 2 would drop) * dropped frame * noise level * field forwarded frame At last, if you can do very tiresome work, edit pulldown cycle list by hand, feed it with -O to retry. -- KAWAMATA/Hitoshi --- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click ___ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
Re: [Mjpeg-users] Re: yuvkineco with good capture
Thanks for the information. I was never real clear which 'c' values to use. Might be useful to update the man page to indicate reasons to lower/raise it. I'd been using nuppelrec for about 6 months with good results run through yuvkineco - an occasional glitch but not bad. I modified nuppelrec to write lzo-compressed 'raw' frames after purchasing a larger drive (I like nuppelrec :-) Anyway, after doing this yuvkineco was worse. Come to find out nuppelrec was dropping a lot of frames but not reporting it as such (Drop: 0 was also displayed, but there were other messages saying it was having problems but continuing - didn't realize that meant it lost a frame...) I've now modified nuppelrec to use fieldnr, changed my large filesystem from reiserfs back to ext3 (ext3 seems to perform better with really large files - had been using ext3 prior to upgrading the drive and wasn't having so many problems). Also made a few 'tweaks' to nuppelrec and am now able to record for a long time without a drop. Have had a recording going for about 90 minutes with other things running on the system and haven't observed a dropped frame come through yet. I'm really pleased with it now. Had also found that whenever my wife changes the speed of the ceiling fan that it causes a little noise to come across that sometimes confuses the card - fieldnr reports more fields than it really received during the time interval, so I have a 'backup' method that uses timestamps to validate the results of fieldnr...though this is a really rare case that takes lots of times flipping the switch to make it fool fieldnr :-) And from previous messages I've started recording interlaced rather than using yuvkineco - but I'm considering moving back to yuvkineco for movies. After all, I'm getting no drops at all while recording now, and since it is raw it oughta' work great with yuvkineco. I gotta' say I've had a lot of fun since I started playing with this stuff last spring. I've learned more than I ever wanted to know about video capture, but now that I've got everything working just about perfect (except the DVD player counts a bit awkward, which I believe Andrew Stevens has a fix for that I've not been able to try yet because I can't build from what I pull from CVS) I'm really enjoying it. -- Ray --- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click ___ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
Re: [Mjpeg-users] recording a powerpoint presentation
Hallo > I want to record a powerpoint presentation to VCD. I will use OpenOffice > to play the presentation. But how do I record the video output to > harddisk? Has anybody done this, or something similar, before? I'd prefer > a software solution. A general answer would be to create jpegs images and then loop a number of frames so the single image is shown for some time. The disadvantage of this is that you have to create a avi file. And use the AVI's than for encoding. auf hoffentlich bald, Berni the Chaos of Woodquarter Email: [EMAIL PROTECTED] www: http://www.lysator.liu.se/~gz/bernhard --- This SF.net email is sponsored by: IBM Linux Tutorials. Become an expert in LINUX or just sharpen your skills. Sign up for IBM's Free Linux Tutorials. Learn everything from the bash shell to sys admin. Click now! http://ads.osdn.com/?ad_id=1278&alloc_id=3371&op=click ___ Mjpeg-users mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/mjpeg-users
