DivX5.02 1 pass = 650mb, 2-pass, first pass =18mb file ?!?!

[DaveQB]

i have to set the VBR mode to 1 pass to get a normal sized and playable AVI file

if i try and set to 2-pass, first pass then the same file that encodes fine to a (approx.) 650mb PLAYABLE file comes out at (approx.) 18mb's and unplayable in WMP

tried several files and same result.


any ideas why i cant use 2-pass, first pass ??

have tried both the Pro version and the non-Pro version of DivX5.02

[Dreassica]

because it is just the first pass, it will only create a file with the info needed to make a 2nd pass with better bitrate allocation, u won't get a playable file the fisrst time. AFTER the 1st pass is done, choose 2 pass second pass and then it will create the right file!

[DaveQB]

OH!!!
i never knew that! :)
i couldnt find anything on it!

well thanx for clearing that up for me.

i thought i was doing well (quality wise) with what i had,
so now i can get even better quality ?

*excittedly goes off to encode*

PS do i have to pick a bitrate for the second pass?
should it be the same or what for best quality?
time taken for encoding isnt an issue

[DaveQB]

oh hmmm,
now with 2-pass i am noticing the final size file will be double that of a 1-pass,
ok makes sense,
so i should use half the bitrate then to have the same size file as a 1-pass??

therefore, the question is, is there a quality benefit to using 2-pass if the final sized file needs to be XXX mb's ??

[Acaila]

now with 2-pass i am noticing the final size file will be double that of a 1-pass,
ok makes sense, so i should use half the bitrate then to have the same size file as a 1-pass??No, absolutely not. The 2-pass method should not result in a double sized clip. If you input the same bitrate for both modes they should result in a file of the same size (bitrate=size). Could you check the DivX5 Guide (http://www.doom9.org/gknot-main3.htm) to see if you did everything correctly?

therefore, the question is, is there a quality benefit to using 2-pass if the final sized file needs to be XXX mb's ??That's what 2-pass exists for, to get the best possible quality for your available space by optimizing the bit allocation. The 1-pass methods can't look ahead in the video, 2-pass mode first analyzes it then encodes it so it can look ahead.

[DaveQB]

hmm interesting
the predicted file size is slowing coming down, but it wont make the same size file that the one did (bout 620mb's i recall)

this one is currently predicted at ....872mb's
and is at 670 mb's right now

i may have punched in a lsightly differnt bitrate,
got mixed up what i was doing here (encdoing DivX and SV-CD's and capturing here) :D

so if i run the 2-pass, twice, leaving all settings the same , (ie bitrate) i should have the same sized file as a 1-pass would result, but with better quality just taking twice as long to do.
am i right ?? do i win the car! :D

[DaveQB]

this is how i have been working out what bitrate to use to fit on a CD.. been very accurate til now, is there a better way?

42:10 minutes = (42*60)+10
= 2530 seconds

650mb's / 2530 = .256917 mb's per second

therefore 256K's/Second

256*8 = 2048 bitrate

[Acaila]

Seems about right. But how about substracting the audio bitrate though?

[FactorM]

are those 650mb only for video? If not you have to subtract the audio bitrate from your calculated video bitrate.

And my calculation would look like this:

650mb = 665600kb

665600kb / 2530s = 263 kb/s

263 * 8 = 2104 kbit/s


edit: little bit too late :)

[hermanthegerman]

Don't be surprised if you end up with a file much smaller than 650MB. The bitrate of about 2000kb/s is very high. Depending on your movie the codec won't probably need such a high bitrate to get max quality. So he will reduce bitrate automatically and this will result in a smaller file.

Servus,
hermanthegerman

[DaveQB]

ok, must of done something wrong first time thru,

at a bitrate of 2045 i am getting a projected file size of 578

was aiming for 620-30 oh well, close enough

didnt calculate audio

i guess i dont coz at 7k's/second (14mb) its not too much to be concerned about

thanx for the help guys!

PS one thing i noticed was the 2-pass encoding looks a little cleared but has a slight fuzz, snow to it.

dunno if its worth all the effort

[jggimi]

There's this great bitrate calculator out there, Dave, that I'd recommend you try, for a variety of reasons:[list=1]
It will run a 2-pass DivX encoding for you....
It can also transcode audio for you, and will recalc bitrate if needed
It can test compressability for you, to increase the accuracy of the final file size...
It can automate resizing and aspect ratio...
Most DivX encoders use it....
It allows you to adjust the major DivX 5 Pro encoding parameters....
Doom9 recommends it...
It's the bees knees (and other insect erogenous zones)...
[/list=1]

Gordian Knot.

[DaveQB]

oh ok,

this is in place of Virtual Dub ??

i thought Virtual Dub was the s#!t ??

it seems witht his program, Nandub and virtual VCR that VD isnt that good after all....

i'll have a look at it, thanx!

[Acaila]

GordianKnot uses VirtualDub to encode, it's a frontend that is very useful for calculating things.

[jggimi]

The current version, GKnot 0.26, is a bitrate calculator and encoding suite that includes:

SmartRipper, Vstrip, DVD2AVI, AviSynth, Virtual Dub, Nandub, Vobsub, DivX3.11Alpha, Azid, LAME, BeSweet, and is used for encoding SBC or DivX5.

Check out Doom9's guide and the Gknot faq for more info.

[theReal]

it seems witht his program, Nandub and virtual VCR that VD isnt that good after all....

Nandub is a VDub mod especially made for Divx3.11 SBC encoding, plus it handles AC3 audio muxing and double-audio avis. Apart from that, VDub is the same (and the best!!)

[DaveQB]

oh ok,
thanx all for clearing this up,

i am learning, trial and error :D