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• 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.

  


• Extract the English audio of video file using ffmpeg

  19 août 2019, par HappyFace

  I like to extract the English audio stream of a video file using ffmpeg. Also, if the file doesn’t have an English audio stream, I want to extract all audio streams. Preferably with a language suffix in their names, if their languages is known.

• How to let ffmpeg download partial m3u8 video without download the full ones ?

  15 octobre 2018, par 3142 maple

  I want to get a video from a m3u8 stream from range : 21:24 22:54.
  I found a answer at https://superuser.com/questions/758943/ffmpeg-cut-for-time-range , and it said I can use -ss 00:21:24.00 -t 90 to cut it.

  But I found that ffmpeg is actually download the whole video until 00:21:24.00 rather that just download 21:24 22:54 .
  How can I let it just download the 90 seconds I want ?

  The command I came up :

  ffmpeg -i "M3U8URL" -acodec copy -vcodec copy -ss 00:21:24.00 -t 90 output.mp4