If I choose the bitrate, does 2-pass do anything?

After having all the problems I’ve been having with 2-pass encoding (previously in XP and Vista… now mainly in Vista), I’m beginning to wonder something… if I select the bitrate of the video, then is 2-pass encoding actually doing anything? Is the 2nd pass making “everything” better, or is it just there to help hit a target filesize if that is specified? I know I know, “try it on a video and find out.” But… to my naked eye, I probably wouldn’t notice if it was doing something, so I’m looking for a programmatic answer from people that are smart on how then 2nd pass of encoding works.
Thanks!

i asked someone that once before and they said that if you set up a 2pass the only thing that happens is that the program goes back through the file once more to verify that the file was completed correctly. in other words, it isnt gonna go back and see if it missed any frames of the movie, its just gonna go back to check if the bitrate or file size is correct in accordance with the settings.

like i said though, thats what someone else told me. cant say that its gospel but hey he’s the one going to computer graphics school…not me.

Encoding Method:
Fast encoding (1-pass): only 1 pass encoding.
High quality encoding (2-pass): the first pass encoding is a get information process, and the second pass is the real encoding. Video quality and output file size estimate improved over one-pass; takes a little longer.

http://dvdfab.com/docs/index.php/Main/DVDToMobileGeneric

As a general rule, 2 pass provides better quality video than one pass. Some will say ALWAYS use 2 pass, some will say NEVER USE IT.

What is supposed to happen is that the first pass analyses the video totally and works out where compression is best applied, motion, etc and then implements that on the second pass.

That being said, if the file is encoded at lower resolutions or displayed at lower resolutions, the difference will most probably be indiscernable.

Only when displayed on larger screens at higher resolutions does it become evident.

So really, it is a trade off for basically double the encoding time for a small improvement in quality.

As it is really only computer time being wasted, I always use 2 pass, but you really have to see what is acceptable to you so that you can make a value judgement.

[QUOTE=GregiBoy;1970664]As a general rule, 2 pass provides better quality video than one pass. Some will say ALWAYS use 2 pass, some will say NEVER USE IT.

What is supposed to happen is that the first pass analyses the video totally and works out where compression is best applied, motion, etc and then implements that on the second pass.

That being said, if the file is encoded at lower resolutions or displayed at lower resolutions, the difference will most probably be indiscernable.

Only when displayed on larger screens at higher resolutions does it become evident.

So really, it is a trade off for basically double the encoding time for a small improvement in quality.

As it is really only computer time being wasted, I always use 2 pass, but you really have to see what is acceptable to you so that you can make a value judgement.[/QUOTE]

Yeah as you say it’s really a question of priorities.

I always burn to DVD and I’m in no hurry so I always use 2 pass but if you’re converting for something with a small screen like for example an ipod it’s probably time wasted.

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