[FFmpeg-user] 2 pass encoding with hevc_nvenc

[Peter White]

04.09.2016 14:31, Reindl Harald:
>
>
> Am 04.09.2016 um 14:24 schrieb Peter White:
>> 04.09.2016 14:00, Reindl Harald:
>>>
>>>
>>> Am 04.09.2016 um 13:57 schrieb Peter White:
>>>> But I never saw the point of running two passes to improve the quality
>>>> of a file encoded with CRF mode. The quality improvement must be very
>>>> small, I reckon. But the encoding time doubles--not worth it
>>>
>>> with smart params it don't double
>>>
>>> the first pass can be with a faster profile and skip audio entirely and
>>> so it's typically around 50% of a normal run and often far below
>>
>> But that then defeats the point of having a /useable/ 1st-pass file. ;)
>
> says who?

I do.

> are you sure you understand how 2-pass-encoding works?

Pretty much, no expert, though. But what do I get when I use a faster
profile for the video in the 1st pass? A file with inferior video
quality to what I want. And the bitrate in CRF mode is highly dependent
on the encoder settings, so I would not have a bitrate estimate for the
2nd pass that is representative. Plus, no audio, if I go with your whole
suggestion.
The idea in my original example is to have a file with all the bells
and whistles after the 1st pass already. And if one fancies, improve on
that in a 2nd pass.
Your method is just another approach to 2-pass encoding with a
throw-away 1st pass.


Peter