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virtualdub, divx, calculating bitrate
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GeJe
Newbie
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12. May 2003 @ 23:55 |
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ok, i´m new to this, so i red the article at
http://www.afterdawn.com/articles/archive/dvd2divx_anamorphic.cfm
and followed the instructions carefully, several times already, but somehow the calculated bitrate doesn´t give the expected result
i´ve got a movie on dvd (PAL 16:9, 93min), i´ve got all the software from that article and went thru it step by step to make a backup of that dvd
the dvtool tells me, i shall set the video bitrate to 867kbit/sec to fit on an 80min cd-r
if i do that and run it thru virtualdub, i get 2 files:
moviename_firstpass.avi (size 92MB)
moviename_secondpass.avi (size 422MB)
and that obviously is not what i wanted
now forgive me my stupidity and tell me what am i doing wrong?
1.) the secondpass.avi seems to hold the entire movie, but of course in a very low quality since it has only 422MB, so whats the firstpass.avi good for? or do i need to merge these somehow?
2.) using my own calculation instead of dvtool, i get the same result, so why has the file less size than calculated and how to calculate the proper bitrate?
3.) what else might i be doing wrong?
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Clove
Suspended due to non-functional email address
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14. May 2003 @ 21:45 |
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My problem is the same only opposite... I over-shot my size estimate by about 300M.
It was a very dark avi, and my bitrate was set quite low, 592k.
Do we need to just tweak our bitrate?
Is DIVX overriding us somehow?
-Clove
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powerdup
Senior Member
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15. May 2003 @ 16:32 |
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Geje: Before encoding the video is analysed to understand its complexity:how many high motion scences and low-motion scenes. Thats what the 1st pass does, it goes through the video gathering info on how to efficiently distribute bits to create good looking video as well as stay within the target bitrate you allowed the codec to use. The 2nd pass uses the info obtained by the 1st pass and encodes the video with it. So basically the actual encoding is done by the 2nd pass.
ok youre movie might have been saturated which means the codec has encoded your video at the best quality and so the filesize is as big as its going to get. Im not too sure if this is your problem because as you said video is low quality. Unless your basing this opinion because of low file size. Take a look at your movie again and see if its pretty good looking or just plain crap. If it is crap, id suggest getting the newest release of the divx codec:divx 5.05. If your movie is pretty good and all you want is to increase the file size then you could could increase the resolution and increase the bitrate or uncheck B-Frames.
Clove: not sure what you mean, is your file under sized or over-sized? If it is then lower resolution or lower bitrate, but in my opinion bitrates less than 600 is not ideal for a feature length movie, i usually get crappy video with bitrates that low.
Life is but a dream...so wake me up already!!!
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Clove
Suspended due to non-functional email address
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17. May 2003 @ 01:13 |
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My file came out much bigger than I expected.
I wouln't worry about it, but it was by a 200M or so.
It had a lot of action, and really didn't look that bad at all.
I don't really want to decrease the bitrate too much lower, like you said, but if it doesn't look that bad as is, maybe I can afford to...
I'm trying to back-up two 1-hour episodes per disc, I'll probably end up just giving that one it's own...
But I would be interested in any ideas, in case I run into this for a longer backup that might do the same thing.
Thanks,
-Clove
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GeJe
Newbie
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17. May 2003 @ 01:36 |
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well, that answer explains what the firstpass is good for, but on the rest it doesn´t help much
i just tried to encode another DvD, and since that one is a long movie in perfect DvD quality, i wanted to split it into 2 CD-R´s,
same as before, i´ve set the bitrate to 1790 as calculated by DVtool, and expected a 1400MB file, but what i got instead was only 704MB and comparing to the DvD the quality is real junk
since its mathematical impossible to fit 97min x 60sec * 1790bit = 1.3GB + 114MB audio into 704MB filesize, still the same question, wtf is virtualdub/divx doing with my settings? why does it reduce the set bitrate by about 50%?
yes i got the latest divx and quality is by far not matching other DvD rips i´ve seen elsewhere, even if other (older) rips r using an older version of divx
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powerdup
Senior Member
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17. May 2003 @ 03:11 |
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ok geje can you tell me exactly the settings you used and the name of the dvd?
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powerdup
Senior Member
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17. May 2003 @ 03:13 |
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OK clove i suggest visiting doom9.org and reading their guides, they use gordian knot, which will help you a lot in getting a filesize that you want as well as having pretty damn good quality.
Life is but a dream...so wake me up already!!!
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GeJe
Newbie
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18. May 2003 @ 02:39 |
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i followed precisely the help article i mentioned above, did all settings exactly as shown there
smartripper, dvd2avi, vfapi, dvtool, cdex, virtualdub, simply everything exactly as shown
the only variable in it is always the bitrate which i at first set as calculated by dvtool
by now i even tried it several more times with different settings, i.e. bitrate 3500 (guessing that doubling the bitrate might result in a proper file if divx cuts it by half again)
but the result is even worse, while i had a file of 704MB with bitrate 1790, at bitrate 3500 the file i got had only 686MB (does this make any sense?)
movies i tried 4 different ones by now, all between 90 and 115 min all with almost same result, so it cannot be a matter which movie it is
(all the movies r PAL, 16:9, 25fps, one is interlaced (and yes i used the deinterlace filter), the other 3 progressive, one i cropped to 640x280 the other 3 r matching 640x360)
and finally i got dvd2svcd v1.1.3 yesterday which seems to have no such problem, i let it encode one of those 4 movies last night, and what i found this morning was a file in perfect quality and of course 2 CD-R´s size
but this just for testing, i´d really prefer to create avi´s rather than svcd´s, if only i knew how to
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powerdup
Senior Member
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18. May 2003 @ 15:28 |
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ok that's really strange i mean with a high bitrate like that and having a file only 686 MB. ok one of your mistakes is the resizing of the first vid:640x280, both horizontal and vert. resolutions have to be multiples of 16 for the divx codec to work correctly. How did the other three look like? the ones you resized to 640x360. Also its not a good idea to use high bitrates like 3500 with the multipass method, it tends to not give great results. its really used for lower bitrate encodes like 600/700 etc...Also did you disable the choose your profile option? check box to get into the mpeg 4 tool like bi directional frames, Qpel, GMC? if you did then uncheck everything except for bi-directional frames. Also i think you should try 1 pass quality based if all your files are so small, try at its highest setting of two, that should give you a larger file size.
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