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• ffmpeg : What is the best practice to keep a live connection/socket with a camera, and save time on ffprobe

  15 mai 2022, par Jeff Strongman

  Today... I used the following command : with subprocess.PIPE and subprocess.Popen in python 3 :

  


  ffmpeg -i udp://{address_of_camera} \
  -vf select='if(eq(pict_type,I),st(1,t),gt(t,ld(1)))' setpts=N/FRAME_RATE/TB \
  -f rawvideo -an -vframes {NUM_WANTED_FRAMES} pipe:`


  


  This command helps me to capture NUM_WANTED_FRAMES frames from a live camera at a given moment.

  


  However... it takes me about 4 seconds to read the frames, and about 2.5 seconds to open a socket between my computer and the camera's computer.

  


  Is there a way, to have a socket/connection always open between my computer and the camera's computer, to save the 2.5 seconds ?

  


  I read something about fifo_size and overrun_fatal. I thought that maybe I can set fifo_size to be equal to NUM_WANTED_FRAMES, and overrun_fatal to True ? Will this solve my problem ? Or is there a different and simpler/better solution ?

  


  Should I try to record always (no -vframes flag) store the frames in a queue(With max size), and upon a wish to slice the video, read from my queue buffer ? Will it work well with the keyframe ?

  


  Also... What to do when ffmpeg fails ? restart the ffmpeg command ?

  


• Creating periodic offsets with ffmpeg segment muxer for seamless ffmpeg-concat transitions

  30 janvier 2021, par Soren Wray

  Suppose I begin with a 1 minute video with a framerate output of 24 frames/second and then use ffmpeg's segment muxer to split it into 60 equal parts of 1 second each with the timesptamps reset :

  


  ffmpeg -i input.mp4 -map 0 -f segment -segment_time 1 -reset_timestamps 1 -g 24 output_%03d.mp4

  


  I then use ffmpeg-concat to string output_000.mp4-output_059.mp4 together into a single video with a periodic 0.5 second dreamy transition effect between each segment : ffmpeg-concat -t dreamy -d 500 -o dreamy.mp4 output_*.mp4

  


  Unfortunately, the transition effects introduce a negative 0.5 second offset between the segments, resulting in a video that is 32 seconds in duration. I don't want to deform the audio and video in this manner. I want to use transition effects without changing the duration or creating any other syncing issues. How to best achieve these seamless transitions is the question.

  


  One potential solution would be to add an offset to the segments, e.g. 0.25 seconds at the beginning and end of every segment, such that the segment muxer produces 60 segments of 1.5 second duration from a 1 minute video. In this manner, the 0.5 second transition effects should blend seamlessly into the offsets.

  


  I don't know where to begin to achieve this potential solution. I've read the official guide, but I can't decipher the relevant filter options for this particular use case. ffmpeg-concat doesn't seem to provide any native options around this problem either.

  


• SOLVED ffmpeg : consider increasing probesize error, but it is never satisfied

  27 octobre 2020, par Jaz

  I was trying to use an Arch solution for streaming to twitch today through FFMPEG, but all of my attempts were in vain because of one simple thing on FFMPEG. it says that the probesize is not large enough, so I instinctively increased the probesize value more and more... and now it is -probesize "500M" yet it is still saying it is not enough. here is the code snippet

  


  [x11grab @ 0x5631f846cd00] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #0, x11grab, from ':0.0':
  Duration: N/A, start: 1603397505.341400, bitrate: 1007124 kb/s
    Stream #0:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1366x768, 1007124 kb/s, 30 fps, 1000k tbr, 1000k tbn, 1000k tbc
0: Input/output error


  


  and the code

  


  #!/bin/bash
     INRES="1366x768" # input resolution
     OUTRES="1366x768" # output resolution
     FPS="30" # target FPS
     GOP="60" # i-frame interval, should be double of FPS,
     GOPMIN="30" # min i-frame interval, should be equal to fps,
     THREADS="2" # max 6
     CBR="1000k" # constant bitrate (should be between 1000k - 3000k)
     QUALITY="ultrafast"  # one of the many FFMPEG preset
     AUDIO_RATE="44100"
     PROBESZ="500M" # specify a size for the ffmpeg tool to assess frames
     STREAM_KEY="$1" # paste the stream key after calling stream_now
     SERVER="live-mia" # twitch server in miami Florida, see https://stream.twitch.tv/ingests/ for list

     ffmpeg -f x11grab -s "$INRES" -r "$FPS" -i :0.0 -f pulse -i 0 -f flv -ac 2 -ar $AUDIO_RATE \
       -vcodec libx264 -g $GOP -keyint_min $GOPMIN -b:v $CBR -minrate $CBR -maxrate $CBR -pix_fmt yuv420p\
       -s $OUTRES -preset $QUALITY -tune film -acodec aac -threads $THREADS -strict normal \
       -bufsize $CBR -probesize $PROBESZ "rtmp://$SERVER.twitch.tv/app/$STREAM_KEY"


  


  even though it was a solution to store in .bashrc, I stored it in a script to call manually.

  


  and if this is helpful, here is the fancy banner ffmpeg shows before the error

  


  ffmpeg version n4.3.1 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-librav1e --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. 51.100 / 56. 51.100
  libavcodec     58. 91.100 / 58. 91.100
  libavformat    58. 45.100 / 58. 45.100
  libavdevice    58. 10.100 / 58. 10.100
  libavfilter     7. 85.100 /  7. 85.100
  libswscale      5.  7.100 /  5.  7.100
  libswresample   3.  7.100 /  3.  7.100
  libpostproc    55.  7.100 / 55.  7.100