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• How to concat videos with FFMPEG without a black frame in the middle

  21 juillet 2020, par david k

  I need to join two videos together programmatically, and FFMPEG seems to be working perfectly except it leaves a single black frame between the two joined videos.

  


  Based on this post, I'm guessing it's because the video and audio streams aren't exactly the same length (not sure why). Since I'm seeing a black flash, I'm guessing that the audio is slightly longer than the video, but I can't figure out how to remedy that. I'm fine losing a tiny piece of the audio at the end of the file.

  


  Can anyone help me "trim" the end of my audio stream so that it matches my video stream ? I need to be able to do this for many files, so I can't just hard-code a value into my command.

  


  I've attempted both of the methods that FFMPEG provides to concat, and both of them have this issue. I'd be fine with either approach, if I can get rid of the black frame.

  


  Transcode :

  


  ffmpeg -i video1.mp4 -i video2.mp4 -filter_complex \
  "[0:v][0:a][1:v][1:a] concat=n=2:v=1:a=1 [outv] [outa]" \
  -map "[outv]" -map "[outa]" output.mp4


  


  Re-wrap :

  


  ffmpeg -f concat -i files.txt -c copy output.mp4


  


  Here is the output of ffmpeg -i video1.mp4 -i video2.mp4 :

  


  ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  built with Apple clang version 11.0.0 (clang-1100.0.33.16)
  configuration: --prefix=/usr/local/Cellar/ffmpeg/4.2.2_1 --enable-shared --enable-pthreads --enable-version3 --enable-avresample --cc=clang --host-cflags='-I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.0.1.jdk/Contents/Home/include -I/Library/Java/JavaVirtualMachines/adoptopenjdk-13.0.1.jdk/Contents/Home/include/darwin -fno-stack-check' --host-ldflags= --enable-ffplay --enable-gnutls --enable-gpl --enable-libaom --enable-libbluray --enable-libmp3lame --enable-libopus --enable-librubberband --enable-libsnappy --enable-libtesseract --enable-libtheora --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwebp --enable-libx264 --enable-libx265 --enable-libxvid --enable-lzma --enable-libfontconfig --enable-libfreetype --enable-frei0r --enable-libass --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-librtmp --enable-libspeex --enable-libsoxr --enable-videotoolbox --disable-libjack --disable-indev=jack
  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
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  5.100 /  5.  5.100
  libswresample   3.  5.100 /  3.  5.100
  libpostproc    55.  5.100 / 55.  5.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'video1.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2020-07-20T20:43:05.000000Z
  Duration: 00:00:09.88, start: 0.000000, bitrate: 1330 kb/s
    Stream #0:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 32000 Hz, mono, fltp, 53 kb/s (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:05.000000Z
      handler_name    : AAC audio
    Stream #0:1(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 1280x720, 1274 kb/s, 25 fps, 25 tbr, 30k tbn, 60k tbc (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:05.000000Z
      handler_name    : H.264/AVC video
      encoder         : AVC Coding
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'video2.mp4':
  Metadata:
    major_brand     : mp42
    minor_version   : 0
    compatible_brands: isommp42
    creation_time   : 2020-07-20T20:43:06.000000Z
  Duration: 00:00:11.68, start: 0.000000, bitrate: 1346 kb/s
    Stream #1:0(und): Audio: aac (LC) (mp4a / 0x6134706D), 32000 Hz, mono, fltp, 53 kb/s (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:06.000000Z
      handler_name    : AAC audio
    Stream #1:1(und): Video: h264 (Baseline) (avc1 / 0x31637661), yuv420p, 1280x720, 1289 kb/s, 25 fps, 25 tbr, 30k tbn, 60k tbc (default)
    Metadata:
      creation_time   : 2020-07-20T20:43:06.000000Z
      handler_name    : H.264/AVC video
      encoder         : AVC Coding
At least one output file must be specified


  


• getting black screen while trying to record dockerized lxde using ffmpeg

  29 mars 2023, par Itzik.B

  I have created a docker image that has LXDE and TightVNCServer.

  


  # Pull base image.
FROM ubuntu

# Install LXDE and VNC server.
RUN apt-get update
RUN apt-get install -y xvfb
RUN DEBIAN_FRONTEND=noninteractive apt-get install -y lxde-core lxterminal tightvncserver
RUN rm -rf /var/lib/apt/lists/*
RUN touch /root/.Xresources
RUN touch /root/.Xauthority
COPY xstartup /root/.vnc/xstartup
RUN chmod +x /root/.vnc/xstartup
#Install Node.js & npm

# Define working directory.
WORKDIR /data

COPY * /data

RUN apt-get install -y ffmpeg


  


  I am running this container using this command :

  


  docker run -it --rm -v /data:/data -p 5901:5901 -e USER=root ubuntudsktp  bash -c "vncserver :1 -geometry 1280x800 -depth 24 && tail -F /root/.vnc/*.log"


  


  I am logging into this container using VNC and running this command to record the whole screen :

  


  ffmpeg -f x11grab -i :1.0 output.webm


  


  After the recording was over, I opened the video and I could see that the video is completely blank(black screen).

  


  this is also my input when i try to run glxinfo :

  


  # glxinfo | grep "OpenGL renderer"
Error: unable to open display


  


  I have also tried to run it using :

  


  DISPLAY=:1 ffmpeg -f x11grab -i :1.0 output.webm


  


  And the results are the same.

  


  What I am missing here ?

  


• Scan video file to detect black page or color/bar tone

  7 février 2023, par sol

  commandline script that will scan bar and tones using nodejs and ffmpeg

  


  ffmpeg -i sample.mp4 -vf -loop 1 -i colorbars.jpg -filter_complex \ "[0:v][1:v]blend=difference:shortest=1,blackframe" \ -an -f null -