x264 and settings for CBR

[ski]

I want to create CBR video using x264 and can't figure out the correct settings. I am creating good baseline profile H.264 using x264, I just want to confim it is CBR. Maybe I'm already doing it- I specify the bit rate on the command line (and frankly, the video looks CBR, but I don't have any tools that give me playback stats and I must be sure).

Does the bitrate tolerance setting have something to do with this? I leave it at the default of 1. Also, any tools out there that give playback stats during local playback? I know many players do when streaming, but those features are off for local playback.

Thanks for your help.

[dionoea]

Code: Select all

--sout-x264-qcomp <float> QP curve compression (0.0=CBR to 1.0=QCP)

hope that helps,

[ski]

I've not seen the qcomp argument in the windows version of VLC- I'm using 0.84a. All I've seen is

--sout-x264-tolerance <float>
Bitrate tolerance

If I can just use x264 preferences (vice command line) to set this, that would be fine. qcomp is not there, though, only bitrate tolerance.



I'll try qcomp, but my command line is a little different than some (but it works) and so I can't tell where to put the parameter you have suggested.

".\halflife_30sec_20fps_01.avi" --sout=#transcode{venc=x264{keyint=6},vb=350,scale=0.5,fps=20,acodec=mp4a,ab=48,channels=2}:duplicate{dst=std{access=file,mux=mp4,url=".\halflife_cbr.mp4"}} vlc:quit

Thanks again.

[The DJ]

0.8.4a only had very early support for H264
If you work with H264 you always need to use the VERY latest

[Trax]

You need to specify a vbv-maxrate instead of quants. See my comment in "CBR mode in x264" post: viewtopic.php?t=21961

[rahulsharma]

Hello folks,

We are also facing certain problems related to fluctuating bitrates by VLC. I would like to know in particular is VideoLan developers have taken a note of this allready? Can anyone lead me to the ticket / track No. where the bug related to such fluctuations is accepted.

looking forward for a prompt reply.

Regards
Rahul Sharma

[DJ]

There are no bugs related to fluctuating bit rates in x264. This is a feature and is called ABR (Average bit rate)

[The DJ]

Yes please stop calling it a bug, and start learning.