D2SRoBa Conditional Sizing Pass -- Why?

brett · 18th January 2004, 11:42

I can understand the reason for a Conditional Sizing Pass in D2SRoBa when your target is undersized or oversized. That's obvious. But...

Why is there a "Q over" option for the Conditional Sizing Pass? If your movie is 100% on target, why do you want a sizing pass just because it has a high Q? Is this actually supposed to help quality? If so, in what way does it help? I mean, if it helps, I'll just leave it at 25 or lower since I usually encode at night.

Manolito's post here seems to imply that the "Q over" sizing pass is totally useless:
Does a sizing pass always improve quality?

If this is true, why does the option exist?

tylo · 18th January 2004, 19:11

Look from this post:
http://forum.doom9.org/showthread.ph...117#post411117

The CCE manual says something like : Q1 ~ 40 : Priority of quality over compressability. Above this, CCE will do compromizes on bitrate allocation. I guess this is what can be improved by doing more passes, but I haven't done any comparisons on this.

bobwillis · 18th January 2004, 23:39

Hi,

My 'test' was done with Saving Private Ryan (region 1). The Q of this movie is over 70. If you look at chapter 9 (the scene in the church when Miller talks to Oppem), black blocking is obvious on Miller's face with a single OPV pass. The improvement with the additional VBR pass was pretty obvious to me.

I didn't do any more comparative tests, but this proved to me that enabling the sizing pass was a good idea for high Q material.

Regards,
Bob

18th January 2004, 11:42	#1 \| Link
brett Registered User Join Date: Nov 2001 Posts: 177	D2SRoBa Conditional Sizing Pass -- Why? I can understand the reason for a Conditional Sizing Pass in D2SRoBa when your target is undersized or oversized. That's obvious. But... Why is there a "Q over" option for the Conditional Sizing Pass? If your movie is 100% on target, why do you want a sizing pass just because it has a high Q? Is this actually supposed to help quality? If so, in what way does it help? I mean, if it helps, I'll just leave it at 25 or lower since I usually encode at night. Manolito's post here seems to imply that the "Q over" sizing pass is totally useless: Does a sizing pass always improve quality? If this is true, why does the option exist?

18th January 2004, 19:11	#2 \| Link
tylo Author of D2SRoBa Join Date: Mar 2003 Posts: 483	Look from this post: http://forum.doom9.org/showthread.ph...117#post411117 The CCE manual says something like : Q1 ~ 40 : Priority of quality over compressability. Above this, CCE will do compromizes on bitrate allocation. I guess this is what can be improved by doing more passes, but I haven't done any comparisons on this. Last edited by tylo; 18th January 2004 at 19:18.

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18th January 2004, 23:39	#3 \| Link
bobwillis Registered User Join Date: Oct 2003 Posts: 218	Hi, My 'test' was done with Saving Private Ryan (region 1). The Q of this movie is over 70. If you look at chapter 9 (the scene in the church when Miller talks to Oppem), black blocking is obvious on Miller's face with a single OPV pass. The improvement with the additional VBR pass was pretty obvious to me. I didn't do any more comparative tests, but this proved to me that enabling the sizing pass was a good idea for high Q material. Regards, Bob