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Old 26th December 2014, 16:07   #10  |  Link
gamebox
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Join Date: Nov 2011
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Thanks a lot, qwill

Quote:
Originally Posted by rwill View Post
AQ Mode = 1 should have a positive impact on your type of content because it lowers the quality of macroblocks with high variance and raises the quality of macroblocks with low variance. So high contrast patterns will get less bits and low contrast patterns will get more bits.
Yes, it did help, and I use AQ 1 most of the time doing encodes. However, in the case of this video value of 0.5 for AQ strength gave better results than the default 1.0.

Quote:
Originally Posted by rwill View Post
You should still set Trellis to 2 as this is a coding efficiency optimization which will save some bits and improve quality at the cost of encoding speed. It also enables the encoder to "see" what a macroblock will look like earlier instead of delaying this to the final encode of the macroblock.
Trellis 2 and value of 0.15 brought significant change here. The end quantizer was improved to 26-27 instead of 27-28, at about 15-20% speed penalty. It seems to me though some textures (eg. faces) got a bit "simpler" and "smoother" and lost some details, but blocking is reduced on "medium" complexity textures and increased only in "lowest" complexity ones, so the end result is less blocking overall (though this might actually be quantizer related).

Quote:
Originally Posted by rwill View Post
You can try to set the deblocking parameters back to 0,0 or even try 1,1 so the background gets blurred more. While this goes against the artistic intend of your scene description it might help to further improve overall quality.
I lowered deblocking to -1,-1 before as default 0,0 made H264 videos noticeably "softer" to me than what I got used to see with XVID. I had that impression of softness even with quantizers like 24-25, especially in areas of high motion where I still prefer (slight) blocking over complete smoothness. I don't know, however, whether lower deblocking decreases compression efficacy (increases quantizers) and by how much.

Quote:
Originally Posted by rwill View Post
You should be careful with enabling all partitions ( p4x4 ) because a Level of 3.0 or higher imposes certain restrictions on the number of motion vectors in two consecutive macroblocks, which I think x264 will violate.
I encode targeting level 4.1 (more like 4.0 since I use low bitrate), as the videos are mostly 720p. I consider playing the video on my Radeon series 4 GPU a "standalone-compatibility test" of sort, as UVD decoder built into it should be pretty much "standard" in its capabilities and features. It refused decoding some clips which were clearly breaking the spec (too many reference frames, etc).

Quote:
Originally Posted by rwill View Post
You can try if disabling MbTree helps visual quality in your case, --no-mbtree.
I never thought about changing mbtree parameter, as I thought it was always beneficial as some sort of RDO optimization for B-frames. I should give this a try for this particular movie (I will continue using it on the ones with normal visual "lineup" - sharp actors, dark and blurred background).

Quote:
Originally Posted by rwill View Post
If you "encode once, decode many" you should always throw as much processing power at the encode as you can. Some hours or even days of CPU time should not matter if the total time of decodes goes into months or years. So use these veryslow/placebo presets.
Yes, that's what I do. I process movies for storage primarily, so I aim for best possible coding and PSY efficiency. Typical 720p movies of about 90 minutes get processed in about 30-40 hours on my single core Athlon64.

And regarding Trellis - what exactly does it do? It seems to me it is some sort of quantization pre-step which "simplifies" macroblocks before coding, making them compress somewhat smaller. That is somewhat similar to quantization matrices used in XVID before, right? I disliked Trellis in XVID for analog captures back in the days as I was getting clearly less details I cared for, but in X264, for digitally sourced material, it seems to bother me somewhat less (though I still alternatively see frames which look better with Trellis and the ones which don't).

Last edited by gamebox; 26th December 2014 at 18:22.
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