~ % ffmpeg -f x11grab -video_size 1366x768 -framerate 45 -i :0.0 -f alsa -i default -preset ultrafast -crf 18 -probesize 42M -pix_fmt yuv420p cyclehit.mp4
ffmpeg version n4.2.3 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 10.1.0 (GCC)
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-fontconfig --enable-gmp --enable-gnutls --enable-gpl --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libdav1d --enable-libdrm --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libiec61883 --enable-libjack --enable-libmfx --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-libsoxr --enable-libspeex --enable-libsrt --enable-libssh --enable-libtheora --enable-libv4l2 --enable-libvidstab --enable-libvmaf --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxcb --enable-libxml2 --enable-libxvid --enable-nvdec --enable-nvenc --enable-omx --enable-shared --enable-version3
  libavutil      56. 31.100 / 56. 31.100
  libavcodec     58. 54.100 / 58. 54.100
  libavformat    58. 29.100 / 58. 29.100
  libavdevice    58.  8.100 / 58.  8.100
  libavfilter     7. 57.100 /  7. 57.100
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
[x11grab @ 0x5602407665c0] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, x11grab, from ':0.0':
  Duration: N/A, start: 1594618549.499365, bitrate: N/A
    Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1366x768, 45 fps, 1000k tbr, 1000k tbn, 1000k tbc
Guessed Channel Layout for Input Stream #1.0 : stereo
Input #1, alsa, from 'default':
  Duration: N/A, start: 1594618549.533270, bitrate: 1536 kb/s
    Stream #1:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
File 'cyclehit.mp4' already exists. Overwrite ? [y/N] y
Stream mapping:
  Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  Stream #1:0 -> #0:1 (pcm_s16le (native) -> aac (native))
Press [q] to stop, [?] for help
[alsa @ 0x560240770100] ALSA buffer xrun.
[swscaler @ 0x5602407c7800] Warning: data is not aligned! This can lead to a speed loss
[libx264 @ 0x5602407ba440] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX
[libx264 @ 0x5602407ba440] profile Constrained Baseline, level 3.2, 4:2:0, 8-bit
[libx264 @ 0x5602407ba440] 264 - core 159 r2999 296494a - H.264/MPEG-4 AVC codec - Copyleft 2003-2020 - 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=0 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=250 keyint_min=25 scenecut=0 intra_refresh=0 rc=crf mbtree=0 crf=18.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=0
[alsa @ 0x560240770100] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
Output #0, mp4, to 'cyclehit.mp4':
  Metadata:
    encoder         : Lavf58.29.100
    Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv420p(progressive), 1366x768, q=-1--1, 45 fps, 11520 tbn, 45 tbc
    Metadata:
      encoder         : Lavc58.54.100 libx264
    Side data:
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 128 kb/s
    Metadata:
      encoder         : Lavc58.54.100 aac
[x11grab @ 0x5602407665c0] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
frame=  747 fps= 51 q=-1.0 Lsize=    2499kB time=00:00:16.57 bitrate=1234.9kbits/s dup=88 drop=86 speed=1.13x
video:2254kB audio:230kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.608863%
[libx264 @ 0x5602407ba440] frame I:3     Avg QP: 9.67  size:350404
[libx264 @ 0x5602407ba440] frame P:744   Avg QP: 9.66  size:  1688
[libx264 @ 0x5602407ba440] mb I  I16..4: 100.0%  0.0%  0.0%
[libx264 @ 0x5602407ba440] mb P  I16..4:  0.2%  0.0%  0.0%  P16..4:  1.4%  0.0%  0.0%  0.0%  0.0%    skip:98.5%
[libx264 @ 0x5602407ba440] coded y,uvDC,uvAC intra: 42.8% 8.5% 8.1% inter: 0.8% 0.2% 0.2%
[libx264 @ 0x5602407ba440] i16 v,h,dc,p: 66% 23% 11%  1%
[libx264 @ 0x5602407ba440] i8c dc,h,v,p: 88%  9%  3%  0%
[libx264 @ 0x5602407ba440] kb/s:1111.91
[aac @ 0x5602407bc380] Qavg: 198.486
Exiting normally, received signal 2.