[FFmpeg-user] ffserver with libvpx-vp9 problem

[Cley Faye]

2016-03-31 11:24 GMT+02:00 Moritz Barsnick <barsnick at gmx.net>:

> a) Why are you using "-pass 1"? AFAIU it will still create an encoded
> video, but it is really meant for multi-pass encoding.
>
> b) What do you intend to achieve with "-b:v 0"? No video in the world
>    can compress that well. ;-) (I'm not aware of any special semantics
>    of the value '0' either.)
>

About that, I can enlighten you: "-b:v 0" ​is used for Constant Quality
encoding for vp9; it works with -crf to determine the "visual quality" of
the video. Setting both -b:v and -crf result in constrained quality (like
constant quality with a maximum bitrate value).

A good read on this: https://trac.ffmpeg.org/wiki/Encode/VP9
However, there is no mention of multiple passes, and it wouldn't do much
good in constant quality encoding anyway, as two-pass is used to improve
variable bitrate encoding (at least for other codecs).