the Goal:
I am trying to record a specific X display on a remote server with a command line tool.
the Problem:
The output file contains a pure black video stream for the whole duration of the recording.
My Approach: I am connecting to a remote server via x2go. The Server runs Ubuntu 16.04.2 with Xfce Desktop Environment. The Display I try to record is :50 (which gets created when I connect to the x2go server). I can control the remote server totally fine through x2go.
My commands for recording via ffmpeg (or avconv/recordmydesktop, which use ffmpeg underneath) all look more or less the same and are like this:
ffmpeg -f x11grab -r 25 -s 1854x1176 -i :50.0 -c:v libx264 screencast.mkv
Sample output:
user@machine:~/$ ffmpeg -f x11grab -r 25 -s 1854x1176 -i :50.0+0,0 -c:v libx264 -vb 4000k -an screencast.mkv
ffmpeg version N-86766-g264f6c6 Copyright (c) 2000-2017 the FFmpeg developers
built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
configuration: --prefix=/home/user/ffmpeg_build --pkg-config-flags=--static --extra-cflags=-I/home/user/ffmpeg_build/include --extra-ldflags=-L/home/user/ffmpeg_build/lib --bindir=/home/user/bin --enable-gpl --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree
libavutil 55. 67.100 / 55. 67.100
libavcodec 57.100.104 / 57.100.104
libavformat 57. 75.100 / 57. 75.100
libavdevice 57. 7.100 / 57. 7.100
libavfilter 6. 95.100 / 6. 95.100
libswscale 4. 7.101 / 4. 7.101
libswresample 2. 8.100 / 2. 8.100
libpostproc 54. 6.100 / 54. 6.100
[x11grab @ 0x1fd9b40] XFixes not available, cannot draw the mouse.
[x11grab @ 0x1fd9b40] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, x11grab, from ':50.0+0,0':
Duration: N/A, start: 1500041497.684675, bitrate: N/A
Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1854x1176, 25 fps, 1000k tbr, 1000k tbn, 1000k tbc
File 'screencast.mkv' already exists. Overwrite ? [y/N] y
Stream mapping:
Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x1fe3040] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x1fe3040] profile High 4:4:4 Predictive, level 4.2, 4:4:4 8-bit
[libx264 @ 0x1fe3040] 264 - core 148 r2643 5c65704 - H.264/MPEG-4 AVC codec - Copyleft 2003-2015 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=1 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=abr mbtree=1 bitrate=4000 ratetol=1.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, matroska, to 'screencast.mkv':
Metadata:
encoder : Lavf57.75.100
Stream #0:0: Video: h264 (libx264) (H264 / 0x34363248), yuv444p, 1854x1176, q=-1--1, 4000 kb/s, 25 fps, 1k tbn, 25 tbc
Metadata:
encoder : Lavc57.100.104 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/4000000 buffer size: 0 vbv_delay: -1
[swscaler @ 0x1fe94e0] Warning: data is not aligned! This can lead to a speedloss
frame= 179 fps= 36 q=-1.0 Lsize= 16kB time=00:00:07.04 bitrate= 18.8kbits/s speed=1.43x
video:14kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 12.869934%
[libx264 @ 0x1fe3040] frame I:1 Avg QP: 6.00 size: 518
[libx264 @ 0x1fe3040] frame P:45 Avg QP: 0.44 size: 81
[libx264 @ 0x1fe3040] frame B:133 Avg QP: 0.94 size: 73
[libx264 @ 0x1fe3040] consecutive B-frames: 0.6% 1.1% 0.0% 98.3%
[libx264 @ 0x1fe3040] mb I I16..4: 0.0% 100.0% 0.0%
[libx264 @ 0x1fe3040] mb P I16..4: 0.0% 0.0% 0.0% P16..4: 0.0% 0.0% 0.0% 0.0% 0.0% skip:100.0%
[libx264 @ 0x1fe3040] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 0.0% 0.0% 0.0% direct: 0.0% skip:100.0%
[libx264 @ 0x1fe3040] final ratefactor: -23.85
[libx264 @ 0x1fe3040] 8x8 transform intra:100.0%
[libx264 @ 0x1fe3040] coded y,u,v intra: 0.0% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 0x1fe3040] i16 v,h,dc,p: 0% 0% 100% 0%
[libx264 @ 0x1fe3040] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 0% 0% 100% 0% 0% 0% 0% 0% 0%
[libx264 @ 0x1fe3040] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x1fe3040] kb/s:15.56
Using: Ubuntu 16.04.2 LTS
I have successfully accomplished to capture the display :50 with "simplescreenrecorder", but that tool has no command line interface. It uses ffmpeg also, so it somehow should be possible to caputure the display but I can´t get it to work properly.
Issue is resolved. I simply swapped x2go for a combination of xvfb and x11vnc and everything is working just fine. Below is the approach, which is working perfectly fine for me. Hope it´s helpful, otherwise I could provide additional info.
user@machine:~/$ Xvfb :50 -screen 0 2560x1440x24 -ac +extension GLX +extension RANDR +render -noreset &> /dev/null &
user@machine:~/$ export DISPLAY=:50
user@machine:~/$ startxfce4 &> /dev/null &
user@machine:~/$ x11vnc -display :50 --forever -noxdamage -nopw -rfbport 5900 -scale 1920x1080 &"
and connect to the vnc server with xvnc4viewer (example below/can be seen in x11vnc startup log)
user@machine:~/$ xvnc4viewer -viewonly -FullScreen hostname:0