What video properties does preset influence?

[Anakunda]

Hello,

whose actually video characteristics is preset switch impacting?
I guess the slower conversion is chosen, the higher ratio quality/bitrate, ie. in quality mode this impacts lower bitate at given quality, while in bitrate mode it impacts higher quality at given br. Is something else influenced by speed preset?
I see ref count is set to max on slowest handling, actually does 16 refs increase decoding complexity, therefore CPU utilization?
Are there other changed characteristics than quality/br factor?

[LoRd_MuldeR]

I guess the slower conversion is chosen, the higher ratio quality/bitrate, ie. in quality mode this impacts lower bitate at given quality, while in bitrate mode it impacts higher quality at given br. Is something else influenced by speed preset?

That is basically correct.

However in "quality mode" (i.e. CRF mode) the only thing you know is that 'slower' presets will improve the quality/bitrate ratio and that 'faster' presets will hurt the quality/bitrate ratio, but the file might come out either smaller or bigger at a given CRF value when switching presets/settings. Thus you may need to re-adjust your CRF value.

For details about the individual presets see "x264 --fullhelp" ;)

[nm]

I see ref count is set to max on slowest handling, actually does 16 refs increase decoding complexity, therefore CPU utilization?

More reference frames increase decoder memory consumption, not necessarily CPU utilization.

Are there other changed characteristics than quality/br factor?

Yes, many stream characteristics get changed between the presets (especially the fastest ones) and that may affect decoding in one way or another.

[Anakunda]

More reference frames increase decoder memory consumption, not necessarily CPU utilization.



Yes, many stream characteristics get changed between the presets (especially the fastest ones) and that may affect decoding in one way or another.

OK than can you confirm that video made on slowest preset won't have any performance problems on slower machine, i.e. will play as smoothly as video encoded on default preset?

[nm]

OK than can you confirm that video made on slowest preset won't have any performance problems on slower machine, i.e. will play as smoothly as video encoded on default preset?

Yes, it should play as smoothly.

[AnonCrow]

Compared to default medium preset , the veryslow and placebo presets may actually require 2% to 5% more CPU time to decode.

The ultrafast is a lot faster to decode (but tune fast-decode /w medium is a better choice) , the superfast a little faster.