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Old 5th January 2019, 10:33   #14  |  Link
excellentswordfight
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Join Date: Jul 2017
Posts: 322
Quote:
Originally Posted by asarian View Post
Ok, this is slightly weird. My first x265 test I did as follows, with these 'joke' settings:

Code:
VSPipe f:\jobs\%1.vpy - --y4m | x265 - --y4m --preset placebo --sar 1:1 --aud --profile main --vbv-bufsize 160000 --vbv-maxrate 160000 --level-idc 51 --frames %_frames% --crf %2 --aq-mode 3 --qg-size 64 --rc-lookahead 120 --subme 7 --colorprim bt709 --transfer bt709 --colormatrix bt709 --range limited --output "%3:\video\%1.265"
Then I did a regular x264 test, with the same 5 sec sample:

Code:
VSPipe f:\jobs\%1.vpy - --y4m | x264 - --demuxer y4m --opencl --frames %_frames% --crf %2 --sar 1:1 --aud --nal-hrd none --level 4.1 --preset placebo --vbv-bufsize 70000 --vbv-maxrate 60000 --aq-mode 2 --ref %_reframes% --tune film --output "%3:\video\%1.264"
These are the exact commandlines used in my cmd script, for good measure. CRF = 14 in both cases. Now where it gets weird, is where the HEVC result is actually 39k, vs. 38k for the x264 test (Sic!). The former took an order of magnitude longer to process, though.

Now, how can this be?! The whole idea of trying to transition to HEVC (for me), was so as to get smaller files, not larger ones. Average bitrate of both results is about the same: ca. 21.x MBps.
Its not weird, and these are the results I was anticipating, hence why I thought you were kidding.

Imo the use case for x265 with very low preset with very low crf value are very limited, especially for consumer ripping bellow 4K (and at 4K as well as going with that low of an crf value will result in massive bitrates) Cause the more bits you spend, and the closer to visually lossless you get the less difference will there be between AVC and hevc, and with very small difference it will be very hard to justify the speed cost.

And you cannot really use the same crf value between different encoders and expect simulair behavior that effeciency conclusions can be drawn from, you cant even do that between different presets in x265! Use 2pass and use a bitrate were you are starting to get a degraded picture with x264 and see if you can improve it with x265. Then dail in a crf value that corresponds with the bitrate range were you are please with the quality.

I ripp in the more 18ish range for 1080p blurays, and there I get away with a bitrate arround 6mpbs, were x264 would need closer to 8mbps. This is with a 2.5x speed penalty mind you, and that gives me maybe a 20% bitrate reduction (calculations based on my very subjetive eyes )

Last edited by excellentswordfight; 5th January 2019 at 11:19.
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