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• Feeding a series of images to ffmpeg as each image is created [closed]

  5 février 2013, par Mark Schneider

  I'm trying to use ffmpeg to build a 1280x720 slide-show from a sequence of pictures and videos, but I have concerns about potential disk I/O bottleneck.

  I expect a typical slide-show to have about 50 pictures and 2-3 videos (10-15 seconds each at 30 fps). I would like to show each picture for 3-4 seconds (possibly with a
  Ken Burns effect) with a smooth 2 second crossfade between each set of pictures (or for pictures adjacent to videos - between the picture and the first/last frame of the video).

  Given about 50 pictures, the crossfades alone would amount to about 3,000 images (50 transitions x 2 secs/transition x 30 fps). And I suppose if I implement a Ken Burns effect during each picture's 3-4 second showing, I'd have to provide ffmpeg with individual images for each of those frames. (I'm writing a script in Ruby that will pull a list of images from a database and in turn call ImageMagick to create the individual images for each frame. As I understand it, the RMagick library interfaces with ImageMagick such that the output images come back as in-memory objects without needing to write to disk. FWIW, I'm developing in Windows 8 and will deploy to Heroku.)

  All of the slideshow examples I've found online feed ffmpeg a set of images which have already been created. However, in an effort to avoid waiting on considerable disk I/O, I'd like to feed each image to ffmpeg as the image is created rather than create them all in advance.

  Is there a way to send each image file to ffmpeg on the fly as the file is created in memory ?

• How to record a 5 second video on Raspberry Pi 3 with USB webcam ?

  16 mars 2023, par Feengineer

  Hi i tried to record a video whit a USB-webcam on my RaspberryPi.
When i type ffplay /dev/video0 I do see a live video, but when i try to record it with ffmpeg the video output is like a black screen with like the traffic cone in my VLC media player. I tried saving the video as a .mkv and .mp4 file. Anyone know how to fix this ?

  


  The code i used to record a video is : ffmpeg -f v4l2 -t 5 -framerate 25 -video_size 640x480 -i /dev/video0 output.mkv and ffmpeg -f v4l2 -t 5 -framerate 25 -video_size 640x480 -i /dev/video0 output.mp4
The video did show up in the folder, but it doesn't show video when opening.

  


  edit : I fixed it now by changing the file type to .avi, but if anyone can still explain how to get .mkv or .mp4, let me know :)

  


• Process Multiple Streams using ffmpeg-python

  27 novembre 2019, par C Dorman

  I have a MPEG-2 TS with a stream of video and a steam of KLV metadata. I can use ffmpeg-python to process each of these streams independently. For example, I can get the video stream, process each frames using numpy as shown in the docs. I can also get the data stream and show it in following way (using the library klvdata) :

  process = (
  
      ffmpeg
  
          .input(in_filename)
  
          .output('pipe:', format='data', codec='copy', map='data-re')
  
          .run_async(pipe_stdout=True, pipe_stderr=True)
  
  )
  
  
  
  for packet in klvdata.StreamParser(process.stdout.read()):
  
      packet.structure()
  
  
  
  process.wait()

  How do I do these at the same time ? I need to split the TS data into its streams and process them both, keeping them in sync. ffmpeg by itself can demultiplex the streams into separate files, but how do I handle the streams in python. The KLV has information that I want to show on top of the video stream (recognition boxes).