Opened 10 years ago

Closed 3 years ago

#1486 closed defect (needs_more_info)

stalls / pauses in video every 30 seconds.

Reported by: Troy Gardner Owned by:
Priority: normal Component: undetermined
Version: unspecified Keywords: x11grab
Cc: Michael Niedermayer Blocked By:
Blocking: Reproduced by developer: no
Analyzed by developer: no


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.

Change History (6)

comment:1 by Carl Eugen Hoyos, 10 years ago

Cc: removed

Please test current git head and please use internal encoders instead of those starting with lib* when reporting problems and please provide complete, uncut console output (together with the command line).

If you record only audio or only video, is the problem also reproducible?
What happens if you significantly reduce the resolution?

comment:2 by Michael Niedermayer, 10 years ago

please run it under gdb and interrupt it during a pause then provide backtraces of all threads
repeat 2-3 times

comment:3 by Michael Niedermayer, 10 years ago

Cc: Michael Niedermayer added

comment:4 by -niko-, 10 years ago

Same problem here, I cant do the gdb thing because the freeze are only in the final video so I cant really see when is happening. I already tried with others enconders and I have the same problem. Lower the bitrate and the resolution helped alot, but i need to do it alot. Worked fine at 60 fps for 30 seconds (its a little more but almost constant) using sameq or half of the bitrate and I need to go lower than that to get no freeze.


0:28, 1:00, 1:36, 2:08, etc

PD: English isn't my first language, so if I wrote something wrong sorry. xD

Last edited 10 years ago by -niko- (previous) (diff)

comment:5 by Elon Musk, 3 years ago

Is this still reproducible?

comment:6 by Carl Eugen Hoyos, 3 years ago

Keywords: x11grab added; pause stall freeze capture xllgrab xvfb removed
Resolution: needs_more_info
Status: newclosed
Note: See TracTickets for help on using tickets.