Running webVideoTranscode jobs manually to transcode a video, with the following command: `php maintenance/runJobs.php --type webVideoTranscode`, I notice it hangs forever.
This is the output of the ps command on another shell:
```
jesus@wikidex22:~$ ps aux |grep ffmpeg
php-fpm+ 31120 0.0 0.0 4288 808 pts/2 SN+ 20:00 0:00 sh -c /bin/bash '/home/www/www.wikidex.net/mediawiki-1.30.1/includes/shell/limit.sh' ''\''/usr/bin/ffmpeg'\'' -y -i '\''/data2/mwuploads/public/wikidex/9/95/Pikapicado_LGPE
.webm'\'' -threads 1 -skip_threshold 0 -bufsize 6000k -rc_init_occupancy 4000 -qmin 1 -qmax 51 -vb '\''2048000'\'' -vcodec libvpx -slices '\''4'\'' -f webm -s 1280x720 -aq '\''3'\'' -acodec libvorbis /var/tmp/php-fpm-wikidex/transcode_7
20p.webm965400c454a6.webm 2>&1' 'MW_INCLUDE_STDERR=;MW_CPU_LIMIT=28800; MW_CGROUP='\'''\''; MW_MEM_LIMIT=4194304; MW_FILE_SIZE_LIMIT=3145728; MW_WALL_CLOCK_LIMIT=28800; MW_USE_LOG_PIPE=yes'
php-fpm+ 31121 0.0 0.0 12944 2772 pts/2 SN+ 20:00 0:00 /bin/bash /home/www/www.wikidex.net/mediawiki-1.30.1/includes/shell/limit.sh '/usr/bin/ffmpeg' -y -i '/data2/mwuploads/public/wikidex/9/95/Pikapicado_LGPE.webm' -threads 1
-skip_threshold 0 -bufsize 6000k -rc_init_occupancy 4000 -qmin 1 -qmax 51 -vb '2048000' -vcodec libvpx -slices '4' -f webm -s 1280x720 -aq '3' -acodec libvorbis /var/tmp/php-fpm-wikidex/transcode_720p.webm965400c454a6.webm 2>&1 MW_INCLU
DE_STDERR=;MW_CPU_LIMIT=28800; MW_CGROUP=''; MW_MEM_LIMIT=4194304; MW_FILE_SIZE_LIMIT=3145728; MW_WALL_CLOCK_LIMIT=28800; MW_USE_LOG_PIPE=yes
php-fpm+ 31122 0.0 0.0 11840 796 pts/2 SN 20:00 0:00 /usr/bin/timeout 28800 /bin/bash -c '/usr/bin/ffmpeg' -y -i '/data2/mwuploads/public/wikidex/9/95/Pikapicado_LGPE.webm' -threads 1 -skip_threshold 0 -bufsize 6000k -rc_init
_occupancy 4000 -qmin 1 -qmax 51 -vb '2048000' -vcodec libvpx -slices '4' -f webm -s 1280x720 -aq '3' -acodec libvorbis /var/tmp/php-fpm-wikidex/transcode_720p.webm965400c454a6.webm 2>&1
php-fpm+ 31123 0.0 0.0 12920 2768 pts/2 TN 20:00 0:00 /bin/bash -c '/usr/bin/ffmpeg' -y -i '/data2/mwuploads/public/wikidex/9/95/Pikapicado_LGPE.webm' -threads 1 -skip_threshold 0 -bufsize 6000k -rc_init_occupancy 4000 -qmin 1
-qmax 51 -vb '2048000' -vcodec libvpx -slices '4' -f webm -s 1280x720 -aq '3' -acodec libvorbis /var/tmp/php-fpm-wikidex/transcode_720p.webm965400c454a6.webm 2>&1
php-fpm+ 31124 0.9 0.2 503724 32596 pts/2 TN 20:00 0:00 /usr/bin/ffmpeg -y -i /data2/mwuploads/public/wikidex/9/95/Pikapicado_LGPE.webm -threads 1 -skip_threshold 0 -bufsize 6000k -rc_init_occupancy 4000 -qmin 1 -qmax 51 -vb 204
8000 -vcodec libvpx -slices 4 -f webm -s 1280x720 -aq 3 -acodec libvorbis /var/tmp/php-fpm-wikidex/transcode_720p.webm965400c454a6.webm
jesus 31207 0.0 0.0 12784 1000 pts/1 S+ 20:01 0:00 grep ffmpeg
```
I can reproduce the problem executing the command directly from the command line. The only output I get is the following:
```
ffmpeg version 3.2.9-1~deb9u1 Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 6.3.0 (Debian 6.3.0-18) 20170516
configuration: --prefix=/usr --extra-version='1~deb9u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnut
ls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libebur128 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgs
m --enable-libmp3lame --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-
libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-
libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
libavutil 55. 34.101 / 55. 34.101
libavcodec 57. 64.101 / 57. 64.101
libavformat 57. 56.101 / 57. 56.101
libavdevice 57. 1.100 / 57. 1.100
libavfilter 6. 65.100 / 6. 65.100
libavresample 3. 1. 0 / 3. 1. 0
libswscale 4. 2.100 / 4. 2.100 libswresample 2. 3.100 / 2. 3.100
libpostproc 54. 1.100 / 54. 1.100
/home/www/www.wikidex.net/mediawiki-1.30.1/includes/shell/limit.sh: line 101: 26075 Killed /usr/bin/timeout $MW_WALL_CLOCK_LIMIT /bin/bash -c "$1" 3>&-
```
Then the shell freezes forever. CTRL+C doesn't work. I have to `kill -9` (a simple kill does nothing) the 2 last processes.
After fiddling around with it, the problem is basically the `MW_WALL_CLOCK_LIMIT=28800` parameter. If I set this to 0, then `/usr/bin/timeout` don't get invoked, and the encoding works flawlessly.
My server is Debian Stretch `4.9.0-4-amd64 #1 SMP Debian 4.9.51-1 (2017-09-28) x86_64 GNU/Linux`
I've "solved" the problem by setting `$wgTranscodeBackgroundTimeLimit = 0;` in LocalSettings.php which effectively sets MW_WALL_CLOCK_LIMIT to 0 on the job run.