[FFmpeg-user] x11grab video stalls every 30 seconds in screencapture

[Paul B Mahol]

On 6/26/12, Troy Gardner <troy at troyworks.com> wrote:
> We are using latest ffmpeg, for screencapture in the cloud.

And older version had same issue?

I ask because recently code for multithreaded demuxing have been added.

>
> We are seeing odd dropped frame stalls in video capture every 30 seconds
> for about 1-2 seconds in duration.
> Audio is captured without stalls, and  Audio Video sync is perfectly fine
> despite stalls.
>
> Hoping someone had ideas, this is driving us nuts and there's nothing
> obvious to explain it.
>
> This is the capture setting we are using.
> ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 30 -s 1024x768 -i :0.0  -acodec
> libvorbis -ar 44100 -vcodec libx264 -preset ultrafast -gp 0 -threads 0
> ffg4.mkv
>
> This is the a drop frame test case capture  with lossless x264 that shows
> dropped frames around 25-26 and significant stall errors at 30 and 60
> seconds
> http://66.220.0.170/XFG4.mkv
>
> We get this trying different options, like keyframes.
>
> This is the output  with flashsrv, which shows  similar pause around 23 and
> 53 seconds, and indicates it's not a libx264 specific issue.
> flashsrv http://66.220.0.170/out.mov
>
>
> This is running on an instance with 16 vcpu + 16gb ram, on the Amazon AWS
>  there is no noticeable background process that we can see at least that
> would explaing
> and happens regardless if it's debian, or ubuntu.
>
>
> This is the version of ffmpeg.
> ffmpeg version 0.11.1 Copyright (c) 2000-2012 the FFmpeg developers
>   built on Jun 26 2012 12:42:06 with gcc 4.7.1
>   configuration: --arch=x86_64 --enable-avfilter --enable-vdpau
> --enable-bzlib --enable-libgsm --enable-libschroedinger --enable-libspeex
> --enable-libtheora --enable-libvorbis --enable-pthreads --enable-zlib
> --disable-stripping --enable-gpl --enable-postproc --enable-swscale
> --enable-x11grab --enable-libdc1394 --enable-shared --disable-static
> --enable-libx264 --enable-libvpx --enable-libmp3lame --enable-libfaac
> --enable-nonfree --enable-libopencore-amrwb --enable-libopencore-amrnb
> --enable-version3
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