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• Extract Motion Vectors From x264 source code

  27 mai 2021, par Essam Aly

  If you are familiar with the x264 source code, where in the code I can extract the MV (motion vectors) of each frame ? Can you point please to a line of code I can intercept and save the MVs to disk ?
Thank you.

  


• Adding watermark bitmap over video in android : 4.3's MediaMuxer or ffmpeg

  7 avril 2017, par Alin

  Here is my scenario :

  • Download an avi movie from the web
  • Open a bitmap resource
  • Overlay this bitmap at the bottom of the movie on all frames in the background
  • Save the video on extarnal storage
  • The video length is 15 seconds usually

  Is this possible to achieve using MediaMuxer ? Any info on the matter is gladly received

  I’ve been looking to http://bigflake.com/mediacodec/#DecodeEditEncodeTest (Thanks @fadden) and it says there :

  "Decoding the frame and copying it into a ByteBuffer with
  glReadPixels() takes about 8ms on the Nexus 5, easily fast enough to
  keep pace with 30fps input, but the additional steps required to save
  it to disk as a PNG are expensive (about half a second)"

  So having almost 1 sec/frame is not acceptable. From what I am thinking one way would be to save each frame as PNG, open it, add the bitmap overlay on it and then save it. However this would take an enormous time to accomplish.

  I wonder if there is a way to do things like this :

  1. Open video file from external storage
  2. Start decoding it
  3. Each decoded frame will be altered with the bitmap overlay in memory
  4. The frame is sent to an encoder.

  On iOS I saw that there a way to take the original audio + original video + an image and add them in a container and then just encode the whole thing...

  Should I switch to ffmpeg ? How stable and compatible is ffmpeg ? Am I risking compatibility issues with android 4.0+ devices ? Is there a way to use ffmpeg to acomplish this ? I am new to this domain and still doing research.

  ---

  Years later edit :
  Years have passed since the question and ffmpeg isn’t really easy to add to a commercial software in terms of license. How did this evolved ? Newer versions of android are more capable on this with the default sdk ?

• Recieving multiple files from ffmpeg via subprocesses.PIPE

  19 août 2014, par Per Plexi

  I am using ffmpeg to convert a video into images. These images are then processed by my Python program. Originally I used ffmpeg to first save the images to disk, then reading them one by one with Python.

  This works fine, but in an effort to speed up the program I am trying to skip the storage step and only work with the images in memory.

  I use the following ffmpeg and Python subproccesses command to pipe the output from ffmpeg to Python :

  command = "ffmpeg.exe -i ADD\\sg1-original.mp4 -r 1 -f image2pipe pipe:1"
  
  pipe = subprocess.Popen(ffmpeg-command, stdout = subprocess.PIPE, stderr = subprocess.PIPE)
  
  image = Image.new(pipe.communicate()[0])

  The image variable can then be used by my program. The problem is that if I send more than 1 image from ffmpeg all the data is stored in this variable. I need a way to separate the images. The only way I can think of is splitting on jpeg markers end of file (0xff, 0xd9). This works, but is unreliable.

  What have I missed regarding piping files with subproccesses. Is there a way to only read one file at a time from the pipeline ?