[FFmpeg-user] Picture jerky when screencasting?

[Etienne Buira]

On Sat, Jun 04, 2011 at 06:31:24PM -0700, lugoteehalt wrote:
> 
> Etienne Buira wrote:
> > 
> > On Fri, Jun 03, 2011 at 09:14:21PM -0700, lugoteehalt wrote:
> >> Great thanks.  Seems to be an exact copy.  It now works with:
> > 
> > Make sure of it (you can use diff -s file1 file2).
> > 
> >> ffmpeg -f alsa -ac 2 -i pulse -f x11grab -s cif -r 25 -s `xdpyinfo | grep
> >> 'dimensions:'| awk '{print $2}'` -fpre
> >> /usr/local/share/ffmpeg/libx264-lossless_ultrafast.ffpreset -i :0.0
> >> ~/out.mkv
> >> 
> >> The picture no longer jerks on iplayer fullscreen, nor is it much
> >> webcammy. 
> >> But the quality, while acceptable for most things, is not high.  Colour
> >> gradients are stepped for instance.  Hope this not off topic but could
> >> you
> >> suggest how to tweek the quality - it is a complex piece of software for
> >> someone new?
> > 
> > The command you give is not the initial one, and here, you don't use
> > libx264 at all. Use your initial command, with only -vpre changed to
> > -fpre pointing to a file you know for sure is an exact copy of the
> > original preset.
> > Bear in mind that options ordering matters.
> > _______________________________________________
> > ffmpeg-user mailing list
> > ffmpeg-user at ffmpeg.org
> > http://ffmpeg.org/mailman/listinfo/ffmpeg-user
> > 
> Great thanks.  Did as you asked but the result was the same as before with 
> 
> [libx264 @ 0x9093f40] constant rate-factor is incompatible with 2pass.

Hi

Then, you have a bug I cannot reproduce.

> in red.  The command was:
> 
> ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 25 -s 1360x768 -i :0.0 -acodec
> pcm_s16le -vcodec libx264 -fpre
> /usr/local/share/ffmpeg/libx264-lossless_ultrafast.ffpreset output.mkv
> 
> The preset files are the same used diff like you said.
> 
> Tried strace, don't remotely know if this is relevant but did:

strace -e trace=file is less verbose, but as you are using fpre instead
of vpre, we know yet what preset ffmpeg should load.
(Well, you can give it a try, with -vpre lossless_ultrafast, and grep
strace for 'ffpreset').

> open("/usr/local/share/ffmpeg/libx264-lossless_ultrafast.ffpreset",
> O_RDONLY|O_LARGEFILE) = 9
> 
> so seems like it is going to the correct preset.
> 
> Had not realised I was not using libx264 in the most recent command that
> works, above.  Do not remotely know what I'm talking about but looked for
> libx264 and the only files the thing can presumably find are:

The -vcodec instructs which video codec to use, same with -acodec and
audio. If not specified, it will default depending on the container.

> /usr/lib/libx264.so.112
> /usr/local/lib/libx264.a
> 
> Is it possible it simply has no libx264?  Thanks again.

libx264 is installed as it is the software that tells you [libx264...]
lines.

Last thing I see you might look at is to check if you did any
modification to your git source tree.