XviD 2nd Pass question

Hi, I've been encoding with DivX/XviD and am more than happy with what XviD has to offer - my query is concerning the 2nd pass option - I normally encode at a moderate rate of, say, 1400Kbps (just a single pass).

Does the 2nd pass optimise the video quality whilst maintaining a (relatively) smaller file size, or is the purpose of the 1st pass/2nd pass option just to allow users to specify a target framerate/file size for their encodes?

Thanks for any help in advance,

Jon

 

The multipass purpose is: minumum size keeping a maximum bitrate.

Thet is, if a part of your video has no losses by keeping, say, 400 kbps, that part of video is encoded at 400 kbps (this happens on the credits, for instance).
Aa long as the video images raise in complexity, also the bitrate of that AVI is encreased (but by keeping Bitrate > MAXIMUM BITRATE you set when you set 'multipass XXXX kbps').

For example, a 900 MB AVI (@ 1-pass encoding) could lower to 700 MB without losing any quality (because during the 1st pass the codec scans, durning the 2nd pass it compresses the movie according to the scan result).

The same happens using MP3 VBR (Variable Bit Rate) compression: an audio file compressed using MP3 128 kbps VBR will have a smaller size than an audio file compressed MP3 128 kbps CBR (Constant Bit Rate) but keeping the same quality. But remember: the maximum quality is set @ 128 kbps, it won't be comparable to, say, 160 or 192 kbps. (but if this applicable only to music, because for movies it's better keep CBR compression, ot you'll create an un-sync .MPG if you'll encode .AVI --> .MPG).

Therefore, multipass is simply a method to have smaller file size but keeping the same quality. To have more quality you would have to encrease the bitrate (e.g. '1400 kbps multipass ' is smaller (the amount of 'smaller' is dependent on the movie's characteristics) than '1400 kbps single pass' but worse of '1401 single pass').

 

Hey what are you guys using for software? I love xvid's! I like them better then dvd becuase the quality is so good and they are so small! I would like to take dvd's and make them xvid's. Can you recommend any software?

 

Xvid or DivX, DivX set at 'Encode Performance = Slow' (more time but less size).
The only problem is that DivX must be registered, Xvid is free.
But I think that Xvid and DivX are equivalent...

 

Would I need to rip the dvd first to the hard drive then encode it?

 

My suggestion is to follow http://www.afterdawn.com/guides/archive/dvd2divx_anamorphic.cfm.
I, who like VCD movies, usually do an even easier process (I avoid resizing):
1) VOB --> MPEG-1 with TMPGenc + DVD2AVI plugin
2) MPEG-1 --> AVI with VirtualDub.
In this way, using DivX 'Portable profile' I have a no-loss AVI compression of about 700 MB.
This because most of the quality loss occur in the AVI compression.
If you have a different opinion, use the guide above mentioned...