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• How to write mp4 video file with H264 codec ?

  21 mai 2017, par kramer65

  On OSX I can record from my webcam and write a video file with the following simple script :

  import cv2
  
  camera = cv2.VideoCapture(0)
  
  
  
  # Define the codec and create VideoWriter object to save the video
  
  fourcc = cv2.VideoWriter_fourcc(*'XVID')
  
  video_writer = cv2.VideoWriter('output.avi', fourcc, 25.0, (640, 480))
  
  
  
  while True:
  
      try:
  
          (grabbed, frame) = camera.read()  # grab the current frame
  
          frame = cv2.resize(frame, (640, 480))  # resize the frame
  
          video_writer.write(frame)  # Write the video to the file system
  
  
  
      except KeyboardInterrupt:
  
          camera.release()
  
          break

  The resulting avi file is quite big though. I want a smaller file, preferably an mp4. So I changed the filename to output.mp4 and the fourcc codec to H264. That writes a video file which works, but gives me the following error :

  $ python write_video_file.py 
  
  OpenCV: FFMPEG: tag 0x34363248/'H264' is not supported with codec id 28 and format 'mp4 / MP4 (MPEG-4 Part 14)'
  
  OpenCV: FFMPEG: fallback to use tag 0x00000021/'!???'

  Since I thought I’m missing the H264 codec in ffmpeg I decided to uninstall ffmpeg and opencv and reinstall them again with H264 support. For this I used the following commands :

  # First ffmpeg
  
  brew install ffmpeg --with-fdk-aac --with-libvidstab --with-openh264 \
  
        --with-openjpeg  --with-openssl --with-tools --with-webp --with-x265 --with-zeromq
  
  # then opencv3
  
  brew tap homebrew/science
  
  brew install opencv3 --with-contrib --with-ffmpeg --with-tbb

  After this I ran the script again, using the following combinations :

  • output.mp4 with H264
  • output.mp4 with X264

  Unfortunately I still get the OpenCV warnings/errors. The file is readable, but it still annoys me that I get these errors. Does anybody have any idea how I can make OpenCV write mp4 video file with the H264 codec ?

  All tips are welcome !

• FFMPEG - Merge two videos with timecode sync

  25 mai 2022, par Olivier Rivard

  We are recording 2 videos from 2 cameras. There is a Timecode metadata attached two the 2 videos. But the starting and stopping of the 2 recodings could have a small difference in time. Less than a second, mostly couple of frames.

  


  One of the video has also the audio recording.
We used ffprobe to extract timecode to analyze the difference.

  


  The difference in timecode won't always be the same.

  


  Ex :
video1.mov timecode : 20:41:11:21
video2.mov timecode : 20:41:11:52

  


  This is the current command that we use to combine the 2 videos side by side to have a look similar to a Zoom call. The only issue is that our videos are out of sync.

  


  ./ffmpeg -i video1.mov -i video2.mov -filter_complex "[0:v]pad=iw*2:ih[int]; [int][1:v]overlay=W/2:0[vid]; [0:a][1:a]amix=inputs=2:duration=longest[aud]" -r 30 -map [vid]" -map "[aud]" output.mp4


  


  We want to make sure that the 2 videos are sync by the timecode.

  


  Example of a combine video :


  


• FFMPEG zoompan only applies and shows 3 images out of the many

  26 mai 2018, par Sanjyot Shah

  I am trying to generate a video from images using FFMPEG 4.0 windows built on AWS windows instance using PHP.

  $command2="ffmpeg -r 1/5 -i https://<path>/$images%d.jpg -c:v libx264 -r 5  -t $total_video_time -y  ".trim($video_name)." -i http://<path>/$audio ";
  
  </path></path>

  The above generates the correct video output with all the input images (50 in this case) but without the zoompan effect on the images.

  Now I try to add the zoompan effect for the images using -

  $command2="ffmpeg -r 1/5 -i https://<path>/$images%d.jpg  -filter_complex zoompan=z='zoom+0.002':d=25*4:s=1280x800 -pix_fmt yuv420p  -c:v libx264 -r 5  -t $total_video_time -y  ".trim($video_name)." -i http://<path>/$audio ";
  
  </path></path>

  This will only pick up the first 3 images and apply the zoompan to the first two images or so.

  Can you please help me with this issue ? Any inputs, pointers are welcome too.