same quality at half size?

[roozbeh]

Hi...

i almost spend a week reading this forum,but still i dont know what should i do!!

i have a plenty of mpeg files in my hard and i just want to make the size reduced,half sized!but at same quality!

the problem is i cant understand if the setting is good...i always fear that some quality is lost!

i reached to this point that best codec to use now is xvid but my samples with half sized were that,quality was worst!

what is best setting for makeing them half sized and also best quality!

all of my mpeg files were ripped form vcds so i think lowbitrate!

(sorry if i posted in wrong place...i just saw nobody is interested in any form in converting mpegs to divx for just reducing size...everybody interested in dvd ripping!)

[celtic_druid]

XviD is a lossy codec, anything encoded with it will be of lower quality than the source. How big is your first pass size compared to the source mpg? Also what are you using for the audio and container?

[roozbeh]

Well....

i am a little bit newbie...
but i think ogm is a good choice!
i used mpeg layer 3 for audio ,but didnt know how to use ogg vorbis or if possible wma as audio!(as i think wma is half size of mp3)

i used gordianknot and just set size to half and with the given bitrate it does the rest!

i dont know the size of first pass.
should i look for it?

[Teegedeck]

I hesitate to speak of 'quality' when it comes to VCDs. VCDs usually contain compression artefacts which make XviD's job quite hard; by tendency, recompressing makes artefacts worse, so you need some strong postprocessing. Hmmm...; try filtering with avisynth. Make sure you've got dgdecode.dll in your Avisynth plugin directory (if you don't have it get dgmpgdec at www.avisynth.org/warpenterprises) and type an avs like this:


directshowsource("yourmpeg.mpg")
converttoyv12()
blindpp(cpu=4)


Additionally try some strong, fast denoising. Put removedirt.dll and removegrain.dll (http://forum.doom9.org/showthread.php?s=&threadid=84481) into your plugins directory (make sure you only put in those dlls that fit your cpu! i.e. no "SSE2"-dll for an old Athlon CPU) and try a script like:


directshowsource("yourmpeg.mpg")
converttoyv12()
blindpp(cpu=4)
removegrain()
removedirt(mode=2)


Edit: At h.263 quantizer 4 to 5 I believe your VCDs should come out considerably smaller now. You could also try using a custom-matrix (instead of h.263) that heavily quantizes high frequencies and see whether you like that 'look' better; try Javor's 1CD or Sharktooth's EQM ULR.

[roozbeh]

well when i load your script into virtualdub 1.5.10.1 first it give me 4 assert errors and then blindpp:work in yv12 colorspace

what doest it mean?

[Teegedeck]

That's why I added the line

'converttoyv12()'

[roozbeh]

well thanks
i'll tell you the results