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• 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...

• Unable to find a suitable output format for 'pipe :' pipe: : Invalid argument

  22 août 2017, par Mahi

  When I run this command :

  raspivid -n -vf -hf -t 0 -w 960 -h 540 -fps 25 -b 500000 -o - |
  
  ffmpeg -i - -vcodec copy -an -metadata title="Streaming from raspberry pi camera" \
  
  -f flv $RTMP_URL/$STREAM_KEY

  it returns :

  [NULL @ 0x3414410] Unable to find a suitable output format for 'pipe:'
  
  pipe:: Invalid argument

  How should I tweak my command line ?

• Specifying input duration of .aac with ffmpeg

  28 septembre 2020, par Jademalo

  I had an error with an mp4 recording, and after recovering the video and audio streams I've still got an issue. The aac audio file is 160kb/s CBR. However, ffmpeg returns this when trying to work with it ;

  


  [aac @ 000001187e6944c0] Estimating duration from bitrate, this may be inaccurate
Input #0, aac, from 'result.aac':
  Duration: 00:38:41.01, bitrate: 174 kb/s
    Stream #0:0: Audio: aac (LC), 44100 Hz, stereo, fltp, 174 kb/s


  


  That duration and bitrate is totally wrong. It should be 42 minutes long, and it definitely has a bitrate of 160 kb/s.

  


  This results in the audio being very inconsistently timed, as well as having all sorts of other issues. It's very weird.

  


  Is there any way I can specify that the input is 160 cbr to try and wrangle it back into a usable file ?