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[HELP] Loss of x264 options when selecting a preset - Printable Version

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+--- Thread: [HELP] Loss of x264 options when selecting a preset (/thread-1447.html)

Loss of x264 options when selecting a preset - The_Tinkerer - 11.07.2020

I've always just glossed over this, finally it's bugged me enough to ask about it.

In Hybrid, load any video, go to the x264 tab, and select "constant rate factor (1-pass)" for encoding mode.

The x264 command line looks like:

x264 --preset veryfast --crf 18.00 --profile high --level 4.1 --ref 3 --direct auto --b-adapt 0 --sync-lookahead 15 --qcomp 0.5 --rc-lookahead 40 --qpmax 51 --partitions i4x4,p8x8,b8x8 --no-fast-pskip --subme 5 --aq-mode 2 --vbv-maxrate 62500 --vbv-bufsize 78125 --sar 1:1 --qpfile GENERATED_QP_FILE --non-deterministic --demuxer raw --input-res 1312x960 --input-csp i420 --input-range tv --input-depth 8 --fps 25/1 --output-depth 8 --output "C:\Users\Administrator\AppData\Local\Temp\Lossless.264" -

Now, click the arrow next to "Preset", in my case I use veryslow. The command line changes to:

x264 --preset veryslow --crf 18.00 --profile high --level 4.1 --ref 6 --sync-lookahead 1 --qpmax 51 --vbv-maxrate 62500 --vbv-bufsize 78125 --sar 1:1 --qpfile GENERATED_QP_FILE --non-deterministic --demuxer raw --input-res 1312x960 --input-csp i420 --input-range tv --input-depth 8 --fps 25/1 --output-depth 8 --output "C:\Users\Administrator\AppData\Local\Temp\Lossless.264" -

So, the following command line options have been completely eliminated:

--direct auto
--b-adapt 0
--qcomp 0.5
--rc-lookahead 40
--partitions i4x4,p8x8,b8x8
--no-fast-pskip
--subme 5
--aq-mode 2

Is that by design, or a bug? It's been like that for quite a long time.

Video files seem to look and play fine... so I'm not sure how important this is.  Tongue

RE: Loss of x264 options when selecting a preset - Selur - 11.07.2020

Okay, here's what's happening when applying the 'very slow' preset (slightly simplified).
  • Hybrid applies the 'default/medium'-preset (since all other presets are based on it).
  • Hybrid applies the specific changes of the 'very slow' preset, that differ from the 'medium/default'-preset:
    --b-adapt 2 --bframes 8 --direct auto --me umh --merange 24 --partitions all --ref 16 --subme 10 --trellis 2 --rc-lookahead 60
  • assuming 'x264->Misc->Main->Minimize command line' is enabled, which is the default, Hybrid then:
    • checks which preset best covers the current option
    • replaces these option with the '--preset <presetName>'
    • check whether the rest of the parameters are covered by a tune option, if a tune option fully overlaps with the remaining parameters (doesn't usually happen), then hide those parameters by replacing them with '--tune <name of the found option>
    • hides all options which are covered by the 'medium/default' preset which do not interfere with the previously selected preset and/or tune option.
-> If you want to see the full x264 command line and don't want those simplifications of the commandline parameters simply disable 'x264->Misc->Main->Minimize command line'.

The options you are 'missing' are simply changed to the application of the preset. Applying a preset in x264 differs from applying a tune option, it always means applying the 'default/medium'-preset and then applying the additional changes of the selected preset. (This is how the x264 developers, same for x265, designed it; this is not a Hybrid thing. Smile)

I hope this explains what happens to the options you thing are going missing. Smile

Cu Selur

RE: Loss of x264 options when selecting a preset - The_Tinkerer - 11.07.2020

Thanks very much for the explanation.  Cool