Hello Dan, Brian.
Thank you for your answers. I've been struggling with this issue for a
while and I don't manage to get an almost constant video bitrate in
the output.
It seems I should use the --nal-hrd cbr option to "fill the mux" as
explained in post:
http://forum.doom9.org/archive/index.php/t-159536.html
<http://forum.doom9.org/archive/index.php/t-159536.html>
But I don't manage to use it successfully in Melt neither with
-x264-params, nor with x264opts.
I don't know how to properly translate it to "name=value" melt syntax.
Should I write -x264opts in the command or not?
I have made different tries with no success so far, such as:
vcodec=libx264 nal-hrd=cbr vbv-bufsize=6M vb=3M minrate=3M maxrate=3M
g=15 bf=2 ts=cbr
Changing the line to:
vcodec=libx264 -x264opts nal-hrd=cbr vbv-bufsize=6M vb=3M minrate=3M
maxrate=3M g=15 bf=2 ts=cbr
does not seem to have effect either.
If I do: "melt -query consumer=avformat | grep x264"
It seems I have both options available:
- identifier: x264opts
description: x264 options (libx264)
description: Select the quality for constant quality mode (libx264)
- identifier: x264-params
description: "Override the x264 configuration using a :-separated
list of key=value parameters (libx264)"
description: Set the encoding preset (cf. x264 --fullhelp)
(libx264rgb)
Do you have a melt working example to get a constant video bitrate in
the output?
Thank you,
David
It seems your version of ffmpeg supports both the new and old x264
option. So you can use either.
This has worked for me in the past to get a reasonably CBR output:
x264opts="keyint=30:min-keyint=1:bframes=2:nal-hrd=cbr:pic-struct:weightp=0:crop-rect=0,0,0,4:fps=29.97:bitrate=18000:vbv-maxrate=18000:vbv-bufsize=25000:ref=4:level=4"
Try tweaking it to meet your needs. It also demonstrates the correct syntax.
As I recall, if the bitrate is high enough, and the content is simple
enough (like a solid color or still picture), x264 might not be able to
use all of the available bitrate - even if you specify CBR.
~Brian
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