performance/quality slowest ?

[fredthemasterofpuppets]

Well, I did read most of the topics about new divx 5.1 released. But I did not see clearly the purpose of using slow/slowest mode for encoding. Indeed, does the quality increase so significantly that it's worth such a high drop in speed ? Does anybody make some test and notice the improvement ?

Thanks for your answers.

[jggimi]

Please see Acaila's comments in http://forum.doom9.org/showthread.php?s=&threadid=61150 and, if you need more info, please use the Search button.

[fredthemasterofpuppets]

I've already read Acaila comments and used "search button". But I would have expected a more precise answer concerning quality issues.

Thanks anyway.

[jggimi]

Sorry to have irritated you. I misread your post as "what?" rather than "why?" which is why I responded the way I did. I contritely solicit your forgiveness.

And I'd have been able to give you an answer, had I migrated to 5.1. But I'm still on 5.05. I try to lag releases with major changes by several months, due to the codec's historical teething troubles.

You'll need to await answers from those who've had experience with the product.

[fredthemasterofpuppets]

no problem. English isn't my native language, so it may be crappy, and people can easy misunderstand me.

I'm going to try to look by myself for now. I was just asking, because I'm quite ignorant in the way codecs are working and have barely no knowlegde about what algorithms are used to compress video.

This is what I found on www.divx.com

1. Fastest - This corresponds to the previous "Fastest" Quality mode. No motion estimation is processed. This mode is intended to be used in conjunction with the 1 Pass Quantizer mode (with Q=1 or Q=2), with the scene change threshold set to 1 and with no MPEG-4 features enabled. With this mode, the codec can be used to generate MJPEG like frames. This is very useful for capturing high-quality clips before re-encoding them at a lower bitrate.
2. Standard - The standard mode corresponds to the old "Slowest" mode in previous versions of the DivX Codec. This mode uses the DivX Patent Pending motion estimation algorithm to ensure a good balance of encoding speed and video quality. This has been slightly tweaked in the DivX 5.1 release and has been proven to improve visual quality when compared to the previous version.
3. Slow - This new mode emulates part of the new rate distortion based decisions and demonstrates a good quality improvement compared to the Standard mode.
4. Slowest - This new mode processes ALL rate-distortion based decisions and is recommended only when either a very fast PC is used or the absolute maximum video quality is requested.

Yet, "3. Slow - This new mode emulates part of the new rate distortion based decisions" does not mean anything to me. Any explanation is welcome.

Thanks

[Prettz]

From what I gathered from the explanation where you got those quotes, it would appear that the "rate distortion" controlled by the "Slow" and "Slowest" settings is identical to the rate distortion of Xvid's VHQ. So using the "Slow" or "Slowest" settings is equivalent to changing the VHQ setting in Xvid. The slower the setting, the longer it will search and the more data it will search through to find the best (most efficient) way of encoding each block.

[fredthemasterofpuppets]

ok.
So now, I think we have to wait people to tell if le quality improvement is great enough to use Slow/Slowest mode. I finished a 30 hours encoding using standard for the first pass et slow for the second. The quality is definitly great. but for now I don't have time to do the encoding in standard mode to compare :(

[SeeMoreDigital]

Hi Fred

Personally speaking I've generated encodes using both the slow and slowest modes with the beta versions of DivX 5.1. And in my opinion unless you have a very fast PC (a P4 2.66GHz or above) the benifits of using these modes does not justify the time it takes to generate the encode...... Sorry DivX.

If I were you I would stick with the standard mode for now and learn as much as you can about the settings (Bi-Di, GMC, Qpel etc) as possible.

Do what many of us have done, which is to rip a chapter or trailer from a DVD and encode it using all the DivX modes and settings and then compare them against each other.

However, don't forget that a full movie encode using 2pass VBR will look a lot better than a 3min trailer or a 6min chapter from a DVD.

Cheers

[fredthemasterofpuppets]

Thanks for your answer SeeMoreDigital.
I'm going to look forward Q-Pel, since I never used it before.
I'll do the Trailer test later, when I'll have time.

Regards.