[x264-devel] preset veryfast always generates lower bitrate than veryslow. Why and how to fix?

[Alex KAS]

On 25.11.2016 16:34, Henrik Gramner wrote:
> On Fri, Nov 25, 2016 at 4:04 PM, Alex KAS <alex-kas at altaray.net> wrote:
>> I encoded literally 34 videos in a raw. All the time the command line
>> was identical (-crf 22, etc) apart from filenames and the -preset setting.
>> Every time I got that veryfast creates a file of the smallest size.
>> Even less than placebo or veryslow
> 
> I believe the underlying misunderstanding here is the assumption that
> CRF guarantees a specific constant "quality" (however you chose to
> define that term) regardless of other settings. It doesn't.
> 
> The average quality:bitrate ratio will improve with slower settings,
> but that doesn't mean that the file size will decrease for any given
> CRF value.
> 
> It's completely normal to get a smaller output file size when using
> faster encoding settings, but the quality will also be worse.
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I understand your logic, but I feel it is strange to get exactly one
preset to be different from "average" or "expected" behavior.

Other way around:
Is it too complicate to check whether the part of the code converting
"preset" into really used parameters is written correctly, specifically
for veryfast?

I would do it myself (it is c/c++/asm, correct?) given someone can guide
me up to some extent at least saying where is the relevant piece of code.

Best,
Alex