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| Unofficial VirtualDub Support Forums > Newbie Questions > How Does Multipass Divx5.05 Encoding Work? |
| Posted by: ccarollo Sep 12 2003, 02:34 PM |
| I'd like to try some multipass encoding, but I'm not sure how to do it in VirtualDub/VirtualDubMod. The divx settings don't have a "2 pass" setting -- they've got "1 pass", "1st pass", and "nth pass". When I select anything but "1 pass" it doesn't do multiple passes I end up with a tiny unplayable file. So...what's the trick? |
| Posted by: Cyberman Sep 12 2003, 04:21 PM |
| "2-pass" is a name that doesnīt really fit the newer DivX codecs. Nowadays itīs "n-pass". The "n" you might know from mathematics or related - itīs a placeholder. It stands for any value you want. While 2-pass only has two passes(1-pass and 2-pass), n-pass has more. You have to run at least 2 encodes, which means the following: 1) set settings in Divx, select "1st pass" and run VDub. Or save it as job 2) leave the settings(though you *could* change them) and select "nth-pass". Run it again, or save it. 3) If you saved the runs as job, run them. Voila - youīve got an encoded video. 4) optional, you might run another encode, or two more. AFAIK, with DivX 5.0.5 thereīs no use in more than 3 runs. The idea behind is that in the first run, the codec can analyze the video stream and make notes of it. In the second(or nth run) it can then use the notes to better compress the video. The more runs you make, the better it should compress. In theory, at least. The 1-pass setting does this all in one run - Iīd call it a "quick and dirty" encode. Useful for previewing of edits, but surely not for final encoding. |
| Posted by: ccarollo Sep 12 2003, 04:30 PM |
| Ah, I see. Didn't realize I had to do the multiple passes manually. Easy enough, though. Thanks! |
| Posted by: ccarollo Sep 12 2003, 10:58 PM |
| Hmmm...well, I got it working, but two-pass (while compressing 10% better) looks noticably worse than one-pass. I'm compressing a 720x480 image from DVD to 320x180, with a 1024kb/s bitrate. One-pass is a little blocky, but looks pretty good. Two-pass is sharper, but has a TON of mosquito noise, and the background moves around in large noisy blocks much more noticably. Any idea what I might be doing wrong...? |
| Posted by: Cyberman Sep 13 2003, 06:34 AM |
| Hmm. Interesting. It shouldnīt do that. Thatīs all I can say. Try three passes. Maybe that helps. Sorry. |
| Posted by: ccarollo Sep 14 2003, 04:56 AM |
| Something else might have been going on, like it failing to overwrite an existing file. I was getting similar results with some of the single-pass encodings I was doing. I'll try again. :-) |