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Old 17th September 2008, 17:25   #1  |  Link
ZZZERO
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Use Turbo mode?

What are the opinions as to how much improvement in quality is gained by turning turbo off in some of the presets (say unrestricted 2 pass HQ or unrestricted 2 pass EQ modes). Is it negligible or are there many of you that think turbo mode hurts quality enough that you don't use it?
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Old 17th September 2008, 17:27   #2  |  Link
Sagekilla
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I'm sorry but what are you talking about? Is this a specific GUI you're speaking of?
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Old 17th September 2008, 17:29   #3  |  Link
Audionut
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Quote:
Originally Posted by ZZZERO View Post
how much improvement in quality is gained by turning turbo off


Not much. The speed increase is usually worth the slight quality loss.

edit: although with --b-adapt 2!!!!

Last edited by Audionut; 17th September 2008 at 17:54.
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Old 17th September 2008, 17:31   #4  |  Link
Sharktooth
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Quote:
Originally Posted by Sagekilla View Post
I'm sorry but what are you talking about? Is this a specific GUI you're speaking of?
i think he's talking about megui
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Old 17th September 2008, 17:59   #5  |  Link
EddietheEagle
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It's negligible. I don't worry about it.
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Old 17th September 2008, 18:09   #6  |  Link
ZZZERO
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Yes. Megui. You say use --b-adapt 2!!!! Is that the "Adapt. B-Frames setting" and set it to "2 - Slow"? The presets I looked at have it set to "1 - Fast" with turbo mode on.
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Old 17th September 2008, 18:14   #7  |  Link
Audionut
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Quote:
Originally Posted by ZZZERO View Post
You say use --b-adapt 2!!!! Is that the "Adapt. B-Frames setting" and set it to "2 - Slow"?
It's totally up to you if you want to use it. And if so,

And yes, that is Adapt. B-Frames setting.


edit: with b-adapt 1, the speed gain is worth setting turbo mode.
With b-adapt 2, that could be different depending on source.

See here.
http://forum.doom9.org/showthread.ph...74#post1184974

Then goto the start of that thread and read.

Last edited by Audionut; 17th September 2008 at 18:17.
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Old 17th September 2008, 19:34   #8  |  Link
Quark.Fusion
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AFAIK b-adapt only matters on first pass, so even in "turbo" mode you can use it if you want it in second pass. Specify --b-frames 3 to speed up it. (Or ever 2, depending on source)
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Old 17th September 2008, 20:00   #9  |  Link
kemuri-_9
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Quote:
Originally Posted by Quark.Fusion View Post
AFAIK b-adapt only matters on first pass, so even in "turbo" mode you can use it if you want it in second pass. Specify --b-frames 3 to speed up it. (Or ever 2, depending on source)
all frame decisions are only calculated on the first pass.
b-adapt is ignored on the 2nd pass.

any change in settings from 1st pass to 2nd pass that would normally affect frame decisions on a 1st pass will not change the decisions at all.
it uses the 1st pass .stats and does not change it.
(why .stat hacking has worked for ages for specifying frame types on 2nd passes)

so 'turbo'ing on the first pass will make the first pass go faster, but you get worse decisions to use in the 2nd pass.
it's up to you if you desire this quality/time trade-off.
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Last edited by kemuri-_9; 17th September 2008 at 20:02.
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Old 17th September 2008, 20:19   #10  |  Link
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However, the changes are very, very minimal. Even when I use extreme (--me umh (maybe higher) --merange 32 --subme 7 --trellis 2 --no-fast-pskip, etc.) settings, I usually do "turbo" (fast first pass). If you have a very slow AVS script, though, and you don't want to do a lossless pass, then it may be worth it to do a higher quality first pass, since the encoding is mostly limited by the AVS.
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Old 17th September 2008, 20:27   #11  |  Link
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OK, so what are these 'turbo' settings that MeGUI has so i can compare them to the slower settings i use.

that is, all the settings... the default x264 ones, the default megui ones, and then the settings that the turbo mode specifies.
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Old 17th September 2008, 20:32   #12  |  Link
Ranguvar
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Not sure what MeGUI's turbo is, but this is what I use:

x264.exe --bframes 3 --b-adapt 2 --b-pyramid --deblock -1:-1 --bitrate 6500 --pass 1 --stats "C:\Example.stats" --partitions none --direct auto --weightb --me dia --subme 2 --output NUL --level 3.2 --progress --threads auto "C:\Example.avs"

So basically, deblock, bframes, weightb, b-adapt, b-pyramid, and direct (and AQ) matter. Everything else can be slaughtered. A possible idea for a test, also, is doing the first pass with worse AVS filters. This is more touchy, though. For example, with degraining, do the first pass and try to get the same amount of grain lost, just use fast filters even if they kill a good amount of detail.
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Old 17th September 2008, 20:37   #13  |  Link
kemuri-_9
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this whole thread is based on megui turbo as far as i can tell, so the settings from that are necessary.
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Old 17th September 2008, 20:47   #14  |  Link
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In my x264 lossless test --subme 3 was same speed as --subme 2 and in recent builds were some speed optimisations to --subme 1. Also it seems that --b-adapt 2 depends on motion estimation settings.
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Old 17th September 2008, 21:05   #15  |  Link
cyberbeing
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MeGUI's 1st pass turbo mode is something like this but largely depends on what options are chosen (I haven't listed all options and possibilities):

--pass 1 --bitrate XXXX --bframes XX --b-pyramid (if set for pass 2) --b-adapt 1|2 --direct auto --filter X:X (set the same as pass 2) --subme 1 --partitions none --me dia --threads auto --thread-input --progress --no-dct-decimate (if set for pass 2)

Kemuri, why not just download a build of MeGUI that you can fool around with? It shows you the x264 cli it uses when you change settings.

Last edited by cyberbeing; 17th September 2008 at 21:14.
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Old 17th September 2008, 22:00   #16  |  Link
Inventive Software
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Wrong forum, for a start! MPEG-4 Encoder GUIs.

@mod: please move this.
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Old 17th September 2008, 23:19   #17  |  Link
ZZZERO
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Really? I thought was asking an encoding question about the turbo settings for a quick first pass and how that affects the quality of the final encode, and that's why I put it in this forum.
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Old 17th September 2008, 23:31   #18  |  Link
fields_g
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Quote:
Originally Posted by Inventive Software View Post
Wrong forum, for a start! MPEG-4 Encoder GUIs.

@mod: please move this.
"Turbo Mode" may be a checkbox in a GUI, but the formation and usage discussions belongs here. People who do 2-pass by command line or batch file are benefited by this discussion. The only benefits for a GUI would be developers who want to tweak their turbo option or people who want to try to convince them to do so.
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Old 18th September 2008, 14:09   #19  |  Link
ZZZERO
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Quote:
Originally Posted by kemuri-_9 View Post
OK, so what are these 'turbo' settings that MeGUI has so i can compare them to the slower settings i use.

that is, all the settings... the default x264 ones, the default megui ones, and then the settings that the turbo mode specifies.
I'd be happy to provide you with those details if I could figure out how to get them. Usually when you change a setting the command line changes in the interface, but when I click or unclick turbo I don't see where it changes so I don't know how to post the difference between turbo on and turbo off here so that I can get some opinions as to how that would affect the final encode. How the command line changes is probably a question I could post in the GUI forum.
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Old 18th September 2008, 15:49   #20  |  Link
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If you want to see what meGUI has done, look in the logs. Otherwise you can browse the source to see what it is doing, I think this is the section:

Code:
  533             if (Turbo)
  534             {
  535                 NbRefFrames = 1;
  536                 SubPelRefinement = 0;
  537                 METype = 0; // diamond search
  538                 I4x4mv = false;
  539                 P4x4mv = false;
  540                 I8x8mv = false;
  541                 P8x8mv = false;
  542                 B8x8mv = false;
  543                 AdaptiveDCT = false;
  544                 MixedRefs = false;
  545                 BRDO = false;
  546                 Trellis = false;
  547                 noFastPSkip = false;
  548                 WeightedBPrediction = false;
  549                 biME = false;
  550             }
http://megui.svn.sourceforge.net/vie...20&view=markup
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