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• Remove Static Pixels from a Video to Mimic a Green Screen Effect [closed]

  2 août 2021, par nKrkan

  I have a video that's 50 seconds in length, resolution of 480x480 and 16 frames per second.

  


  There is a person talking in it, with the background being static I thought if there's a way
  
to remove those static pixels (background) and just extract the moving pixels (foreground)
  
and possibly mimic a green screen effect ?

  


  I was thinking on writing a picture-by-picture comparison tool to do such thing but I don't
  
believe I'm up to the task, or maybe It's laziness.

  


  And now I know, some of you will point out that the video has compression artifacts and that
  
might cause some problems but It doesn't have to be Studio quality stuff.

  


  I tried the ffmpeg command from this question : Remove random background from video using ffmpeg or Python
  
And it does mask the person, but... I couldn't quite get it to work, apparently putting the
  
reference image in the input makes that image burned into the video, thus having no way to
  
remove it, but it did mask the background as black and the person as greenish, so still not a
  
viable way to do it.

  


  Have also tried some Python projects I've found on the GitHub but none of them worked as
  
I expected.

  


  So, what I thought to do is simply compare the first and the second frame of the video, check
  
all the pixels by comparing them with the two sources, and change those that stay within a
  
certain range of the initial pixel value.

  


  I should point out I'm not very knowledgeable with mathematics and the majority of the
  
methods used in these type of things, but perhaps someone could point me to an interesting
  
source to read and learn, or by providing an alternative to the methods aforementioned above.

  


• How to create a video out of frames without saving it to disk using python ?

  6 septembre 2022, par brenodacosta

  I have a function that returns a frame as result. I wanted to know how to make a video out of a for-loop with this function without saving every frame and then creating the video.

  


  What I have from now is something similar to :

  


  import cv2
out = cv2.VideoWriter('video.mp4',cv2.VideoWriter_fourcc(*'DIVX'), 14.25,(500,258))
for frame in frames:
    img_result = MyImageTreatmentFunction(frame) # returns a numpy array image
    out.write(img_result)
out.release()


  


  Then the video will be created as video.mp4 and I can access it on memory. I'm asking myself if there's a way to have this video in a variable that I can easily convert to bytes later. My purpose for that is to send the video via HTTP post.

  


  I've looked on ffmpeg-python and opencv but I didn't find anything that applies to my case.

  


• ffmpeg How to get PCM floats from AVFrame with AV_SAMPLE_FMT_FLT

  26 novembre 2020, par cs guy

  I have an AVFrame obtained through a decoder that has a format of AVSampleFormat::AV_SAMPLE_FMT_FLT. My issue is I want to convert the data stored inside

  


  avFrame->data; // returns uint8_t *


  


  to Array of floats that are between [-1, +1]. I see that avFrame->data; returns uint8_t * how may I use this to obtain the float pcm data for each channel of the audio ?

  


  I tried the following :

  


  auto *floatArrPtr = (float *)(avResampledDecFrame->data[0]);

    for (int i = 0; i < avResampledDecFrame->nb_samples; i++) {
        // TODO: store interleaved floats somewhere
        floatArrPtr++;
    }


  


  but I am not sure if this is the right way to get data