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• avfilter/af_astats : add noise floor count stat

  17 avril 2020, par Paul B Mahol

  avfilter/af_astats : add noise floor count stat
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/af_astats.c

• Animating a 2D plot (2D brownian motion) not working in Python

  8 avril 2020, par Thamu Mnyulwa

  I am trying to plot a 2D Brownian motion in Python but my plot plots the grid but does not animate the line.

  



  Attempted at performing this plot is below,

  



  !apt install ffmpeg

import matplotlib
matplotlib.use("Agg")
import matplotlib.pyplot as plt
import matplotlib.animation as animation


np.random.seed(5)


# Set up formatting for the movie files
Writer = animation.writers['ffmpeg']
writer = Writer(fps=15, metadata=dict(artist='Me'), bitrate=1800)


def generateRandomLines(dt, N):
    dX = np.sqrt(dt) * np.random.randn(1, N)
    X = np.cumsum(dX, axis=1)

    dY = np.sqrt(dt) * np.random.randn(1, N)
    Y = np.cumsum(dY, axis=1)

    lineData = np.vstack((X, Y))

    return lineData


# Returns Line2D objects
def updateLines(num, dataLines, lines):
    for u, v in zip(lines, dataLines):
        u.set_data(v[0:2, :num])

    return lines

N = 501 # Number of points
T = 1.0
dt = T/(N-1)


fig, ax = plt.subplots()

data = [generateRandomLines(dt, N)]

ax = plt.axes(xlim=(-2.0, 2.0), ylim=(-2.0, 2.0))

ax.set_xlabel('X(t)')
ax.set_ylabel('Y(t)')
ax.set_title('2D Discretized Brownian Paths')

## Create a list of line2D objects
lines = [ax.plot(dat[0, 0:1], dat[1, 0:1])[0] for dat in data]


## Create the animation object
anim = animation.FuncAnimation(fig, updateLines, N+1, fargs=(data, lines), interval=30, repeat=True, blit=False)

plt.tight_layout()
plt.show()

## Uncomment to save the animation
#anim.save('brownian2d_1path.mp4', writer=writer)


  



  However, instead of performing the plot the program is printing,


  



  How do I animate this plot ? I am new to python so I apologize in advanced if this is an easy question.

  



  I found this question on http://people.bu.edu/andasari/courses/stochasticmodeling/lecture5/stochasticlecture5.html , there is a walkthrough of how this code came to being.

  


• ffmpeg : how can i hstack 2 videos and display a watermark outside the video area

  27 février 2020, par Cédric Kamermans

  I’m new to using ffmpeg and I want to combine two 1920x1080 videos using hstack. The output video also needs to be 1920x1080. At the same time I want to display a watermark at the bottom of the screen (outside the video area) and one in the top middle of the screen.

  So far i managed to make an hstack with padding but the watermark won’t display outside the video area.

  Here is my first attempt :

  ffmpeg -y -i input1.mp4 -i input2.mp4 -i watermark1.png -filter_complex "[0]pad=iw+5:color=black[left];[left][1]hstack=inputs=2","overlay=x=(main_w-overlay_w)*0.95:y=(main_h-overlay_h)*0.95","scale=w=1920:h=1080" Output.mp4

  Here is a comparison of what i get and what i want :

  wrong output desired output

  Any help regarding my problem would be very much appreciated !