ffmpeg to Facebook

 ffmpeg-4.1-64bit-static/ffmpeg \
    -thread_queue_size 2048 \
    -f x11grab \
    -s 1280x720 \
    -r 30 \
    -i :0.0+1280,12 \
    -f lavfi \
    -i anullsrc \
    -c:v libx264 \
    -pix_fmt yuv420p \
    -g 300 \
    -c:a aac \
    -ar 44100 \
    -b:a 128k \
    -preset ultrafast \
    -maxrate 4000k \
    -bufsize 960k \
    -f flv "rtmp://live-api-s.facebook.com:80/rtmp/$KEY"

Using PPAPI flash.
[4822:4822:1207/153511.653432:ERROR:sandbox_linux.cc(379)] InitializeSandbox() called with multiple threads in process gpu-process.
ffmpeg version 4.1-static https://johnvansickle.com/ffmpeg/  Copyright (c) 2000-2018 the FFmpeg developers
  built with gcc 6.3.0 (Debian 6.3.0-18+deb9u1) 20170516
  configuration: --enable-gpl --enable-version3 --enable-static --disable-debug --disable-ffplay --disable-indev=sndio --disable-outdev=sndio --cc=gcc-6 --enable-fontconfig --enable-frei0r --enable-gnutls --enable-gray --enable-libaom --enable-libfribidi --enable-libass --enable-libvmaf --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librubberband --enable-libsoxr --enable-libspeex --enable-libvorbis --enable-libopus --enable-libtheora --enable-libvidstab --enable-libvo-amrwbenc --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzimg
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
[x11grab @ 0x6b3ae40] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, x11grab, from ':0.0+1280,12':
  Duration: N/A, start: 1544214913.195751, bitrate: N/A
    Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1280x720, 30 fps, 1000k tbr, 1000k tbn, 1000k tbc
Input #1, lavfi, from 'anullsrc':
  Duration: N/A, start: 0.000000, bitrate: 705 kb/s
    Stream #1:0: Audio: pcm_u8, 44100 Hz, stereo, u8, 705 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  Stream #1:0 -> #0:1 (pcm_u8 (native) -> aac (native))
Press [q] to stop, [?] for help
[libx264 @ 0x6b4ae00] using cpu capabilities: MMX2 SSE2Fast SSSE3 Cache64 SlowShuffle
[libx264 @ 0x6b4ae00] profile Constrained Baseline, level 3.1, 4:2:0, 8-bit
[libx264 @ 0x6b4ae00] 264 - core 157 r2935 545de2f - H.264/MPEG-4 AVC codec - Copyleft 2003-2018 - http://www.videolan.org/x264.html - options: cabac=0 ref=1 deblock=0:0:0 analyse=0:0 me=dia subme=0 psy=1 psy_rd=1.00:0.00 mixed_ref=0 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=0 threads=6 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=300 keyint_min=30 scenecut=0 intra_refresh=0 rc_lookahead=0 rc=crf mbtree=0 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 vbv_maxrate=4000 vbv_bufsize=960 crf_max=0.0 nal_hrd=none filler=0 ip_ratio=1.40 aq=0
Output #0, flv, to 'rtmp://live-api-s.facebook.com:80/rtmp/1993678504078694?s_ps=1&s_sw=0&s_vt=api-s&a=AbyIKCVEjpexIZ60':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: h264 (libx264) ([7][0][0][0] / 0x0007), yuv420p(progressive), 1280x720, q=-1--1, 30 fps, 1k tbn, 30 tbc
    Metadata:
      encoder         : Lavc58.35.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 4000000/0/0 buffer size: 960000 vbv_delay: -1
    Stream #0:1: Audio: aac (LC) ([10][0][0][0] / 0x000A), 44100 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc58.35.100 aac
[flv @ 0x6b49780] Failed to update header with correct duration.ate=3258.2kbits/s speed=1.02x
[flv @ 0x6b49780] Failed to update header with correct filesize.
frame=  828 fps= 31 q=-1.0 Lsize=   10976kB time=00:00:27.56 bitrate=3261.5kbits/s speed=1.02x
video:10933kB audio:7kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.330961%
[libx264 @ 0x6b4ae00] frame I:3     Avg QP:33.91  size: 49845
[libx264 @ 0x6b4ae00] frame P:825   Avg QP:23.89  size: 13388