The way I understand it, it creates smaller and/or better quality files. During the first pass, it analyses the footage and gets a chancve to workout what bitrate etc for different scenes will work best. So when it comes to do the actual encoding on the 2nd pass, the encoder has more info about whats coming next, so can make better use of available bitrate.
Many people liked 3ivx dualpass, gave better results than single pass, but a bug made it useless with QT7/tiger. However there is a workaround for that bug: http://forums.3ivx.com/index.php?showtopic=83898 For many people it may not be worth the extra time/hassle of going for a 2-pass solution, it depends how much you care about quality/filesize. Try both, and see if the results are worth it. 2-pass should be as much of a hassle as it is with 3ivx (manually starting 2nd pass & doing bug workaround). I think the qt7.0.3 ipod video export option uses 2-pass, another reason why its so slow. Steve of Elbows --- In [email protected], Harold Johnson <[EMAIL PROTECTED]> wrote: > > What was the point of two passes anyway? I'm unfamiliar with this. > > Thanks, > Harold > http://podcasterherald.com > > On 12/30/05, Michael I <[EMAIL PROTECTED]> wrote: > > > > Great! > > The days of 1st pass 2nd pass are over! > > Thanks for the info. > > Aloha. > > *andrew michael baron <[EMAIL PROTECTED]>* wrote: > > > > I have Tiger, QT7 and 3ivx 4.5.1 > > > > I encode to single pass constant bitrate (or single pass average bitrate > > when file is too big) at 6400 kbits/sec [error in software makes this > > setting confusing, but thats what I set it at] > > compressor quality med, high or best, depending on motion complexity of > > footage (I usually preset at med). > > maxium quality Quantizer is around 90%-100% (usually 95%) > > minimum quality quantizer is around 10% > > frames per second is 15. > > keyframs forced every 300 delta frames > > half-pixel motion and four vector motion engaged. > > > > Audio is AAC 44.1 128kbs > > > > On Dec 29, 2005, at 10:35 PM, Stan Hirson, Sarah Jones wrote: > > > > I've been doing some tests with 3ivx and QuickTime, but have not been > > getting� file size economy� that is any better than MPEG4 or H.264.� > > > > I got the idea of usinig 3ivx from the Rocketboom tools documentation. It > > was very helpful and generous, but I'm afraid I need some more guidance > > aboput specific settings.� The whole subject of compression has been, > > quite frankly, something that I've been avoiding because it is so confusing > > with its own language and parameters that, to me, don't make much sense.� > > > > I am developing a vlog that will a lot of footage of horses in motion. I > > am trying to keep the bit rate as low as possible to avoid stuttering while > > showing some sense of motion as clean as possible on DSL bandwidth. > > > > What I am looking for from this list is some pointers to instruction about > > compression that is somewhere between the Freevlog tutorials and the 3ivx > > documentation.� > > > > I'd appreciate any advice. > > > > Thanks > > > > Stan Hirson > > hestakaup.blogspot.com > > > > > > > > > > SPONSORED LINKS > > Individual<http://groups.yahoo.com/gads?t=ms&k=Individual&w1=Individual&w2=Fireant&w3=Typepad&w4=Use&c=4&s=51&.sig=IkmOF87iVVg5aOV5s-5ShQ> > > Fireant<http://groups.yahoo.com/gads?t=ms&k=Fireant&w1=Individual&w2=Fireant&w3=Typepad&w4=Use&c=4&s=51&.sig=H15DYYUHQoulfARYZSKttA> > > Typepad<http://groups.yahoo.com/gads?t=ms&k=Typepad&w1=Individual&w2=Fireant&w3=Typepad&w4=Use&c=4&s=51&.sig=bK2vbSrJUIzcRadddW7krQ> > > Use<http://groups.yahoo.com/gads?t=ms&k=Use&w1=Individual&w2=Fireant&w3=Typepad&w4=Use&c=4&s=51&.sig=RO46LszR1YSPWsK2mib1pA> > > ------------------------------ > > YAHOO! 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