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  #1  
04-13-2004, 07:36 PM
Jimblob Jimblob is offline
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Hi

This question is about 2-pass VBR encoding. When I use the preset video bitrates(min 300, max 2520) I get an mpeg of 790Mb. If I increase the min to 500, I get an mpeg of 670Mb.

Why is that?

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04-13-2004, 07:40 PM
kwag kwag is offline
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Quote:
Originally Posted by Jimblob

Why is that?

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Because TMPEG's 2-pass mode is really bad
That's why we never used it

-kwag
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04-13-2004, 07:58 PM
Jimblob Jimblob is offline
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By your reply, can I assume that CQ does a better job of file sizing when I set the min VBR to 500?

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04-13-2004, 08:18 PM
kwag kwag is offline
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Quote:
Originally Posted by Jimblob
By your reply, can I assume that CQ does a better job of file sizing when I set the min VBR to 500?

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Probably, but you'll have to do file size prediction, which is not 100% bullet proof either
But I didn't know 2-pass with TMPEG was THAT way off, as I just looked at your results

-kwag
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04-13-2004, 08:55 PM
Jimblob Jimblob is offline
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Here's what I've been trying to do. The latest TMPGEnc has a new 2-pass VBR wizard template that boasts an out of standard SVCD that fits 110 minutes. In conjunction with an avs script, my final mpeg size is precise. No need to use CQMatic. The only problem is sometimes the vbr goes too low. Get yourself a scene with fog and the result is blotchy. So, I raised the min vbr to 500 to avoid the fog problem and that is when my output mpeg was only 670Mb. I can't figure out why.
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04-13-2004, 09:11 PM
kwag kwag is offline
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Quote:
Originally Posted by Jimblob
So, I raised the min vbr to 500 to avoid the fog problem and that is when my output mpeg was only 670Mb. I can't figure out why.
Seems it's a common problem with TMPEG's bitrate allocation, because the same things happen in CQ mode.
But then it means that TMPEG doesn't obey the average bitrate
The second pass should maintain the average, no matter what you set MIN or MAX to.
So something is broken in TMPEG.

Have you tried this with a very old version of TMPEG, just for the hell of it
Maybe the .12B versions

-kwag
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04-13-2004, 09:33 PM
Jimblob Jimblob is offline
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I'm not sure what to do at this point. Maybe I'll revisit the CQ world.

Thanks for all your input.
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