[FFmpeg-trac] #1486(undetermined:new): stalls / pauses in video every 30 seconds.

FFmpeg trac at avcodec.org
Tue Jun 26 21:32:21 CEST 2012

#1486: stalls / pauses in video every 30 seconds.
             Reporter:  TroyWorks    |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:
  undetermined                       |  unspecified
             Keywords:               |               Blocked By:
  pause,stall,freeze,capture,xllgrab,xvfb|  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
 Summary of the bug:

 We are using fllgrab for screencapture in the cloud.

 Every 30 seconds for about 1-2 seconds in duration, are pauses in only the
 video. Audio and  Audio Video sync is perfectly fine despite stalls.

 EXAMPLEs: with a four color frame counter drop frame test case

 WITH  lossless x264 dropped frames around 25-26 and significant stall
 errors at 30 and 60 seconds

 We get this trying even different options, like keyframes, bitrate.

 WITH flashsrv, which shows  similar pause around 23 and 53 seconds, and
 indicates it's not a libx264 specific issue.

 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 explain

 It happens regardless if it's debian, or ubuntu.

 How to reproduce:
 Using XVFB open chrome with this test

 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

 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

 Ubuntu (several versions) and Debian, with hardware accelerated
 virtualization (HVM). We've also tried several xwindows and xvfb/xenth
 with same issue.

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1486>
FFmpeg <http://ffmpeg.org>
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