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• How to convert short video clips to TS without sound "gaps" between the segments ?

  10 novembre 2022, par Zvika

  I am trying to convert a sequence of short video files from MP4 to TS using ffmpeg.
I get valid TS files, but when playing them in any HLS player, there is a noticeable short gap in the sound between segment to segment.

  


  If I first stitch all the short video files to a single video file, and convert this file to TS while slicing it to segments, it plays perfectly fine.

  


  To the gory details :
My software creates short video clips that should be concateenated to an output video and streamed as HLS.
Each short clip is an H.264 video file and WAV audio file (I can create other formats if needed).
I then convert each such pair of H.264+WAV to a TS file using ffmpeg :
ffmpeg -y -i seg_0.mp4 -i seg_0.wav -c:a libvo_aacenc -c:v copy -bsf:v h264_mp4toannexb seg_0.ts ffmpeg -y -i seg_1.mp4 -i seg_1.wav -c:a libvo_aacenc -c:v copy -bsf:v h264_mp4toannexb -output_ts_offset 2.01 seg_1.ts ffmpeg -y -i seg_2.mp4 -i seg_2.wav -c:a libvo_aacenc -c:v copy -bsf:v h264_mp4toannexb -output_ts_offset 4.02 seg_2.ts
etc.

  


  and I create an appropriate M3U8 file to play all the short clips as a sequence.
The result is not satisfying, as I have audio gaps between each segment and segment, as you can hear here :
https://rnd3-temp-public.s3.amazonaws.com/HLS_4/out_seg2.m3u8

  


  However, if I concat all the pairs together, and convert the concatenated sequence to TS, while requesting ffmpeg to slice them again to segments, using a command like :
ffmpeg -y -f concat -i mp4_list.txt -f concat -i wav_list.txt -c:a libvo_aacenc -c:v copy -bsf:v h264_mp4toannexb -flags +cgop -g 30 -hls_time 2 out2.m3u8
it plays perfectly OK, as you can hear here :
https://rnd3-temp-public.s3.amazonaws.com/HLS/out2.m3u8

  


  How can I get a clear audio output by still encoding each segment separately ? (It's crucial for my workflow)

  


  Thanks !

  


• FFmpeg / python - command works when run from shell but fails when run from python

  4 avril 2019, par artembus

  I have a python script which should run an ffmpeg command with this function :

  def transcode(in_path, out_path):
  
      cmd = ["ffmpeg", "-y", "-i", in_path, '-vf smartblur=lr=1']
  
      cmd += ["-an", out_path]
  
      print("Running:", " ".join(cmd))
  
      subprocess.run(cmd, stdout=cmdout, stderr=cmdout)

  When I run the python script it fails with this ffmpeg error :

  Running: ffmpeg -y -i raid/orig/scenes/train/5786088.mp4 -vf smartblur=lr=1 -an raid/4K/scenes/train/5786088.mp4
  
  ffmpeg version 2.8.15-0ubuntu0.16.04.1 Copyright (c) 2000-2018 the FFmpeg developers
  
    built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.10) 20160609
  
    configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  
    libavutil      54. 31.100 / 54. 31.100
  
    libavcodec     56. 60.100 / 56. 60.100
  
    libavformat    56. 40.101 / 56. 40.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 40.101 /  5. 40.101
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  2.101 /  1.  2.101
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Unrecognized option 'vf smartblur=lr=1'.
  
  Error splitting the argument list: Option not found

  You can see the command it tries to execute in the first line, when I run it in the command line it works fine. When I run the command in the shell it outputs the same version and parameters of the ffmpeg as written in the error above.

  I feel like I missed something simple yet crucial, anyone can point me to the right direction ?

• python3 openCV VideoCapture only black image (Raspbian Stretch)

  21 juin 2018, par PrimuS

  I have a little python function that analyzes a video, chunks it into one image per second and gives me the most dominant color for that image. (Code can be found here : https://github.com/primus852/python-movie-barcode)

  This works great on my Windows testing environment. However, on my Rasbian Stretch Raspberry Pi Setup it only produces a black image, as the source seems to be black.

  I compiled OpenCV (3.4.1) myself with this great article : https://www.pyimagesearch.com/2017/09/04/raspbian-stretch-install-opencv-3-python-on-your-raspberry-pi/, and it worked perfectly fine. I am using python3 and a virtualenv.

  I tried adding the ffmpeg package : apt install ffmpeg, to no avail.

  2 ideas

  • I compiled the openCV source without support for mkv/mp4/similar ? If so, how would I check that and can I just "re-compile" the whole package ?
  • I am missing codecs, where would I be able to check that ?

  The crucial code (I think) is this :

  cap = cv2.VideoCapture(full_path) are there other options that do not break the majority of my code ? I read about skvideo.io from scikit-video but that does not seem to work with my code...

  I am new to python, any hint is appreciated

  // EDIT, I think it is not a duplicate because I pass the I get no error that the capture cannot be opened and :

  OpenCV FFMPEG support :

  • python -c "import cv2; print(cv2.getBuildInformation())" | grep -i ffmpeg
    • returns : FFMPEG: YES

  FFMPEG Codec :

  • ffmpeg -codecs | grep -i avc (file is using AVC)
    • returns : DEV.LS h264 H.264 / AVC / MPEG-4 AVC / MPEG-4 part 10 (decoders: h264 h264_mmal h264_vdpau ) (encoders: libx264 libx264rgb h264_omx h264_vaapi )

  File PATH

  It exists and the path is correct...

  Any other ideas ? Could it possibly the virtualenv ?

  //EDIT2

  Tried with an AVI file

  works...