[FFmpeg-user] x11grab video stalls every 30 seconds in screencapture
b13253 at gmail.com
Fri Jun 7 08:47:13 CEST 2013
> We are using latest ffmpeg, for screencapture in the cloud.
> 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
> libvorbis -ar 44100 -vcodec libx264 -preset ultrafast -gp 0 -threads 0
> 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
> We get this trying different options, like keyframes.
> This is the output with flashsrv, which shows similar pause around
> 53 seconds, and indicates it's not a libx264 specific issue.
> flashsrv http://220.127.116.11/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
I have been experiencng this problem as well. After it stalls, the video and
audio lost sync. However I noticed that my HDD LED flashes when the video
I think that perhaps Linux kernel is trying to write buffered data to
I wonder if there is a way to switch to write-through mode.
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