[FFmpeg-user] 2 pass encoding with hevc_nvenc

Carl Eugen Hoyos ceffmpeg at gmail.com
Sun Sep 4 14:01:34 EEST 2016

2016-09-04 12:52 GMT+02:00 Peter White <peter.white at posteo.net>:
> 04.09.2016 12:21, Carl Eugen Hoyos:

>>> i am trying to encode with a variable bitrate, 2 pass encoding
>> How is this supposed to work (in a general sense, unrelated
>> to a codec or an implementation)?
>> Two-pass encoding indicates constant bitrate afaict.

This should have been "average bitrate" which is not
the same as variable bitrate.

> No, it does not. If each frame got the same bitrate, which
> is the definition of constant bitrate (CBR)

No, the actual definition of cbr (for mpeg-2 video or h.264)
is very difficult and cannot be part of a short email.
(But using cbr with two-pass encoding makes not much
sense, I believe we agree on that.)

Anyway, my point was that you can either specify a quality
or a bitrate. If you specify a bitrate, two-pass encoding
increases quality. If you don't want an average (but a variable)
bitrate, I don't see how two-pass encoding can help.

Carl Eugen

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