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Re: [Mjpeg-developer] mpeg2enc with MJPEG Tools 1.9.0rc2 buggy !
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From: Christophe D. <cdu...@ma...> - 2007-03-19 11:55:59
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Hi I have the same problem with rc2 ! I encode a DVD with an older version of mpeg2enc (just before rc1) the problem doesn't appear, the quality is perfect. If I use mpeg2enc rc2 with the same video file and the same parameters, the image quality is VERY VERY POOR ! I think it's a bug in rc2, introduce after rc1. I have compiled rc2 on a MacIntel, the speed is good, the quality very poor I have compiled rc2 on a Mac PPC, the speed is VERY VERY SLOOOOOW and the quality very poor. If I try mpeg2enc juste before rc1 on a MacIntel or MacPPC theses problems doesn't appears. I am sure that this is a bug of mpeg2enc, I use mpeg2enc for 3 years now, and I doesn't have seen this problem before 1.9.0 rc2. Christophe On Monday, March 19, 2007, at 08:14AM, "stefan" <st...@sf...> wrote: >stefan schrieb: >>> First, if you are encoding for DVD do *NOT* use '-q 1 -b 9000'! >>> >> >> Which is very mpeg2enc related. I now know several encoders (ffmpeg >> included), which produce a *lot* less bitrate-spikes and seem to avoid >> them completely in 2-pass-mode ... I have even seen some files where >> there have not been any spikes... >> >> >>> If you use "-q 3" or "-q 4" the problem appears to go away. >>> >> Sorry,... not here... :-( >> >>> Ideally and eventually '-q' should go away completely. ALl that should >>> be specified is a desired average bitrate and a tolerance (how much >>> above/below the average is acceptable). >>> >>> >> Huh? I don't regard this to be a good idea. There is no harm, if an >> encoder uses less bits than specified by the bitrate. Imagine a >> completly black frame: P+B frames could be close to zero-size (just the >> overhead to say the decoder "same than before"...). >> >> I think, mpeg2enc needs two bitrate-modes: >> >> 1) variable bitrate-mode: A local and short second pass is just used to >> chop off bitrate-spikes. That is, whenever the encoder realizes that >> there was a spike, it goes back some frames (a GOP?) and reencodes them >> with a lower q-scale again. But only for that spike... >> >> 2) average-bitrate-mode or "filesize-mode": Here it makes some sense to >> specify an upper-bound-tolerance, only. > >and in case someone asks... an average-bitrate, of course... > >> The encoder must not go beyond >> this. If not possible otherwise, then use 2 passes... This mode should >> fit a file as close as possible to a given file-size/average-bitrate... >> >> hmm,... seems like I must use ffmpeg, currently... >> >> cu >> Stefan >> >> >> ------------------------------------------------------------------------- >> Take Surveys. Earn Cash. Influence the Future of IT >> Join SourceForge.net's Techsay panel and you'll get the chance to share your >> opinions on IT & business topics through brief surveys-and earn cash >> http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV >> _______________________________________________ >> Mjpeg-developer mailing list >> Mjp...@li... >> https://lists.sourceforge.net/lists/listinfo/mjpeg-developer >> > > >------------------------------------------------------------------------- >Take Surveys. Earn Cash. Influence the Future of IT >Join SourceForge.net's Techsay panel and you'll get the chance to share your >opinions on IT & business topics through brief surveys-and earn cash >http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV >_______________________________________________ >Mjpeg-developer mailing list >Mjp...@li... >https://lists.sourceforge.net/lists/listinfo/mjpeg-developer > > |
