Encoding XviD using one pass?

[snowman1234]

Hello. I'm new to encoding VOB files into AVI, so I have a couple of questions...

So far, encoding a VOB file using Auto GK takes a lot longer than I'd like, so I was wondering whether it is fine to encode using only one pass (I'd have to get non-auto GK, yes?). What are the advantages and disadvantages of using one pass? Also, are there certain settings I should be using for one pass as opposed to two?

If it helps, I'm encoding to 350 MB. I'm not even sure what a "pass" is, I just know that two of them take longer than one!

So, suggestions?

Thanks a lot in advance

[Irakli]

Originally Posted by snowman1234

Hello. I'm new to encoding VOB files into AVI, so I have a couple of questions...

So far, encoding a VOB file using Auto GK takes a lot longer than I'd like, so I was wondering whether it is fine to encode using only one pass (I'd have to get non-auto GK, yes?). What are the advantages and disadvantages of using one pass? Also, are there certain settings I should be using for one pass as opposed to two?

If it helps, I'm encoding to 350 MB. I'm not even sure what a "pass" is, I just know that two of them take longer than one!

2-pass encoding usually used to hit a particular filesize (e.g. 350 MB in your case). First pass analyses the video to determine how many bits each part of the video needs, etc., and writes this information to stats file. Second pass then uses this stats file to create actual encoded file; because second pass now 'know' everything about video (from stats file), it can successfully hit a particular filesize and, at the same time, vary bitrate in order to provide more or less constant quality accross the video.

In theory, it is possible to use 1-pass encoding to hit a particular filesize by using single pass average bitrate mode (or even CBR), but the disadvantage is that the quality will not be very constant accross the video: some parts will get more bits than necessary, while others will not get enough bits and quality will suffer.

It is also possible to use constant quantizer mode to encode with 1 pass. Advantages: you will get more or less constant quality across the whole video without doing 2-pass encoding. Disadvantages: this mode aims for particular quality level, and the size of final encode is therefore unpredictable in advance.
IIRC, you can easily use this mode in AutoGK by activating Target Quality mode instead of Predefined Size.

Originally Posted by snowman1234

So, suggestions?

Summarising what was said above:

Use 2-pass mode if you want to get good quality at given filesize.
Use constant quantizer mode if you want to get good quality with 1 pass only, but don't care about filesize. This can be activated by selecting Target Quality in AutoGK.
Use 1-pass bitrate mode mode in you want to get particular filesize but target quality is not a very high priority. AutoGK doesn't have this mode.

Originally Posted by snowman1234

Thanks a lot in advance

You're welcome.

[raeltheimperialaerosolkid]

I quote Irakli 100%...
Since filesize is not a matter anymore for me since I started using a DVD writer instead of the old CD writer. I left the 2 pass mode to history and started to use the 1 pass costant quantizer with the maximum satisfaction.

[laserfan]

Yeah I think since DVD burning got cheap the 2-pass method, formerly for hitting CD-sized targets, is of less & less interest.

I made an HD Xvid of an "extreme high action" movie a few weeks ago that was 6800Mb in size, but most every movie I make fits on a DVD-5, even using Xvid in HDTV profile and 2.00 target quant max quality.

[stax76]

Yeah I think since DVD burning got cheap the 2-pass method, formerly for hitting CD-sized targets, is of less & less interest.

Multipass is still more popular I think, probably many people don't really understand the pros and cons of multipass vs quality mode, use multipass because of habit etc.

[dat720]

I like using 2 pass becasue of a couple of things, as already mentioned you end up with a smaller file, the codec can distribute the bandwidth according to where it's needed which is nice as slow scenes will be encoded with a low bitrate, and fast scenes have more bandwidth available to work with so will be less likely to appear blocky. Also it will only use the bandwidth it requires, if you're encoding a slow scence BR/HD movie with a high bitrate like 9000kbps, it will only use what is required, a movie could end up only using half that.

[stax76]

@dat720

I'm not sure you understand quality mode well, there isn't a big difference in filesize/quality/efficiency between quality mode and 2 pass mode.

You can find some explanations here. Similar applies to XviD.