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• FFMPEG screen capture : adjust switches to synchronize video and audio

  22 septembre 2017, par machine_1

  I don’t know much about ffmpeg library and I want to use it for screen capture. What I got basically is several commands from a youtube video and I have an issue, but first, let me list the commands :

  • List devices :

    ffmpeg -list_devices true -f dshow -i dummy

  • video and audio(microphone) :

    ffmpeg -y -rtbufsize 200M -f gdigrab -thread_queue_size 1024 -probesize 10M -r 30 -i desktop -f dshow -channel_layout stereo -thread_queue_size 1024 -i audio="Microphone (Realtek Audio)" -c:v libx264 -r 30 -preset ultrafast -tune zerolatency -crf 25 -pix_fmt yuv420p -c:a aac -strict -2 -ac 2 -b:a 128k "vid_mic.mp4"

  I am using the last one, and I noticed that the video in the output file is faster than the audio, that is to say, they are out of sync. How can I adjust the switches to resolve this issue ? I am using windows 10.

• FFMPEG using a screen capture for an overlay results in serious visual flaws

  3 octobre 2017, par Joey

  I’m trying to overlay a screen capture of a specific window on top of a background image, and output the result - it works but results in unacceptable visual flaws.

  The command I’m using is :

  ffmpeg -loop 1 -r 30 -i background.jpg -f gdigrab -r 30 -i title=Calculator \
  
  -filter_complex "[0:v][1:v]overlay=10:10[video]" -map "[video]" -c:v libx264 \
  
  -f flv output.flv

  which places a screencap of the calculator window on the background at position 10,10.

  This is what the output looks like :

  

  All the buttons on the calculator are super muddied and appear bold, almost as if it was overlaid several times at slightly different positions. Is there something wrong with the command or any way to fix it and preserve visual integrity of the original ? Changing the output format doesn’t have any effect, nor does setting -crf 0 or adjusting any other encoding settings.

  This doesn’t happen when I screen capture just the calculator by itself without overlaying it on anything. For reference here is what the output looks like when I only record the calculator with no overlaying :

  

• FFmpeg 3.3.4 avfoundation to record only a specific section of the screen on macOS Sierra using the command line

  16 octobre 2017, par antedesk

  I’m using FFmpeg version 3.3.4 (installed via brew) through the command line to record my desktop during some automated tests on my macOS Sierra (10.12.6).

  I would like to record only a specific section of the screen but, unfortunately, I’m not able to find the proper options in the documentation to reach my goal.

  According to the FFmpeg documentation for avfoundation, this is the command I use :

  ffmpeg 
  
  -f avfoundation    // avfoundation
  
  -pix_fmt uyvy422   // pixel format
  
  -i 1               // input: desktop
  
  -r 30              // framerate for output
  
  [PATH]/test.mp4      // filename

  When I run this command I have the following output :

  ffmpeg version 3.3.4 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with Apple LLVM version 9.0.0 (clang-900.0.37)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/3.3.4 --enable-shared --enable-pthreads --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-gpl --enable-ffplay --enable-frei0r --enable-libass --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopus --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-opencl --enable-videotoolbox --enable-openssl --disable-lzma --enable-libopenjpeg --disable-decoder=jpeg2000 --extra-cflags=-I/usr/local/Cellar/openjpeg/2.3.0/include/openjpeg-2.3 --enable-nonfree --enable-vda
  
    libavutil      55. 58.100 / 55. 58.100
  
    libavcodec     57. 89.100 / 57. 89.100
  
    libavformat    57. 71.100 / 57. 71.100
  
    libavdevice    57.  6.100 / 57.  6.100
  
    libavfilter     6. 82.100 /  6. 82.100
  
    libavresample   3.  5.  0 /  3.  5.  0
  
    libswscale      4.  6.100 /  4.  6.100
  
    libswresample   2.  7.100 /  2.  7.100
  
    libpostproc    54.  5.100 / 54.  5.100
  
  [avfoundation @ 0x7fb7d4005800] Stream #0: not enough frames to estimate rate; consider increasing probesize
  
  Input #0, avfoundation, from '1':
  
    Duration: N/A, start: 7263.782833, bitrate: N/A
  
      Stream #0:0: Video: rawvideo (UYVY / 0x59565955), uyvy422, 1920x1080, 1000k tbr, 1000k tbn, 1000k tbc
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (rawvideo (native) -> h264 (libx264))
  
  Press [q] to stop, [?] for help
  
  No pixel format specified, yuv422p for H.264 encoding chosen.
  
  Use -pix_fmt yuv420p for compatibility with outdated media players.
  
  [libx264 @ 0x7fb7d4028400] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 AVX2 LZCNT BMI2
  
  [libx264 @ 0x7fb7d4028400] profile High 4:2:2, level 4.0, 4:2:2 8-bit
  
  [libx264 @ 0x7fb7d4028400] 264 - core 148 r2795 aaa9aa8 - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - 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=-2 threads=6 lookahead_threads=1 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=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
  
  Output #0, mp4, to '[PATH]/test.mp4':
  
    Metadata:
  
      encoder         : Lavf57.71.100
  
      Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv422p, 1920x1080, q=-1--1, 30 fps, 15360 tbn, 30 tbc
  
      Metadata:
  
        encoder         : Lavc57.89.100 libx264
  
      Side data:
  
        cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
  
  frame=   83 fps= 28 q=-1.0 Lsize=     525kB time=00:00:02.66 bitrate=1612.6kbits/s dup=1 drop=0 speed=0.889x

  I tried to use the -video_size option to set the video frame size, but it doesn’t work.